essay about water on mars

Water on Mars: Exploration & Evidence

Liquid water may still flow on Mars, but that doesn't mean it's easy to spot. The search for water on the Red Planet has taken more than 15 years to turn up definitive signs that liquid flows on the surface today. In the past, however, rivers and oceans may have covered the land. Where did all of the liquid water go? Why? How much of it still remains?

Observations of the Red Planet indicate that rivers and oceans may have been prominent features in its early history. Billions of years ago, Mars was a warm and wet world that could have supported microbial life in some regions. But the planet is smaller than Earth , with less gravity and a thinner atmosphere. Over time, as liquid water evaporated, more and more of it escaped into space, allowing less to fall back to the surface of the planet.

Where is the water today?

Liquid water appears to flow from some steep, relatively warm slopes on the Martian surface. Features known as recurring slope lineae (RSL) were first identified in 2011 in images taken by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the Mars Reconnaissance Orbiter (MRO). The dark streaks, which appear seasonally, were confirmed to be signs of salty water running on the surface of the planet.

"If this is correct, then RSL on Mars may represent the surface expression of a far more significant ongoing drainage system on steep slopes in the mid-latitudes," a research team member told Space.com in 2012.

In 2015, spectral analysis of RSL led scientists to conclude they are caused by salty liquid water. [Related: Salty Water Flows on Mars Today, Boosting Odds for Life ]

"The detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," the study's lead author, Lujendra Ojha, of the Georgia Institute of Technology in Atlanta, said in a statement . Vast deposits of water appear to be trapped within the ice caps at the north and south poles of the planet. Each summer, as temperatures increase, the caps shrink slightly as their contents skip straight from solid to gas form, but in the winter, cooler temperatures cause them to grow to latitudes as low as 45 degrees, or halfway to the equator. The caps are an average of 2 miles (3 kilometers) thick and, if completely melted, could cover the Martian surface with about 18 feet (5.6 meters) of water. 

Frozen water also lies beneath the surface. Scientists discovered a slab of ice as large as California and Texas combined in the region between the equator and north pole of the Red Planet. The presence of subsurface water has long been suspected but required the appearance of strange layered craters to confirm. Other regions of the planet may contain frozen water, as well. Some high-latitude regions seem to boast patterned ground-shapes that may have formed as permafrost in the soil freezes and thaws over time. 

The European Space Agency's Mars Express spacecraft captured images of sheets of ice in the cooler, shadowed bottoms of craters, which suggests that liquid water can pool under appropriate conditions. Other craters identified by NASA's Mars Reconnaissance Orbiter show similar pooling.

Evidence for water on Mars first came to light in 2000, with the appearance of gullies that suggested a liquid origin. Their formation has been hotly debated over the ensuing years.

But not everyone thinks that Mars contains water today. New research reveals that RSL may actually have formed by granular flows formed by the movement of sand and dust.

"We've thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand," lead author Colin Dundas said in a statement. "This new understanding of RLS supports other evidence that shows that Mars today is very dry."

That idea may have been washed away by the recent discovery of a possible subsurface lake near the Martian South Pole.

An underground lake?

Researchers made a big splash when they announced that Mars might be hiding a lake beneath its southern pole. The European Mars Express spacecraft used its Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to detect the proposed water. Ground-penetrating radar sent radar pulses to the surface, then timed how long it took for them to be reflected. The properties of the subsurface layers affect how long it takes for the beams to return.

MARSIS' investigation revealed that the Martian south pole is composed of multiple layers of ice and dust to a depth of about nearly 1 mile (1.5 kilometers) spread over a 124-mile-wide (200 km) region.  

"This subsurface anomaly on Mars has radar properties matching water or water-rich sediments," Roberto Orosei, principal investigator of the MARSIS experiment and lead author of the new research, said in a statement. 

MARSIS also revealed the presence of a subsurface lake among the pockets. According to the radar echoes, the lake is no more than 12.5 miles (20 km) across, buried nearly a mile beneath the surface. The scientists aren't certain of the lake's depth, but they have confirmed that it is at least 3 feet (1 meter) deep. According to the researchers, the lake must have salt to keep from freezing.

"This is just one small study area; it is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered," Orosei said.

Not all researchers are as certain about the presence of liquid water.

"I think it's a very, very persuasive argument, but it's not a conclusive or definitive argument," Steve Clifford, a Mars researcher at the Planetary Science Institute in Arizona, told Space.com . "There's always the possibility that conditions that we haven't foreseen exist at the base of the cap and are responsible for this bright reflection."

More than three decades ago, Clifford proposed that Mars could harbor liquid water beneath its polar caps in the same way that Earth does. On Earth, lakes beneath the Antarctic and Greenland ice sheets are created when heat from within the planets melt the glaciers in patches. Clifford told Space.com that a similar scenario could happen beneath the Martian polar ice caps.

"The bright spot seen in the MARSIS data is an unusual feature and extremely intriguing," Jim Green, NASA's chief scientist, said in a statement . "It definitely warrants further study. Additional lines of evidence should be pursued to test the interpretation."

"We hope to use other instruments to study it further in the future," Green said.

Searching for an oasis

When Mariner 9 became the first craft to orbit another planet in 1971, the photographs it returned of dry river beds and canyons seemed to indicate that water had once existed on the Martian surface. Images from the Viking orbiters only strengthened the idea that many of the landforms may have been created by running water. Data from the Viking landers pointed to the presence of water beneath the surface, but the experiments were deemed inconclusive. [ Mars Explored: Landers and Rovers Since 1971 (Infographic) ]

The early '90s kicked off a slew of Mars missions . Scientists were flooded with a wealth of information about Mars. Three NASA orbiters and one sent by the European Space Agency studied the planet from above, mapping the surface and analyzing the minerals below. Some detected the presence of minerals, indicating the presence of water. Other data measured enough subsurface ice to fill Lake Michigan twice . They found evidence that ancient hot springs once existed on the surface and sustained precipitation once fell in some areas. And they found patches of ice within some of the deeper craters.

Impact craters offer a view of the interior of the red planet. Using the ESA's Mars Express and NASA's Mars Reconnaissance Orbiter, scientists were able to study rocks ejected from the planet's interior, finding minerals that suggested the presence of water.

"Water circulation occurred several kilometers deep in the crust some 3.7 billion years ago," Nicolas Mangold, of the University of Nantes in France, said in a statement .

But orbiters weren't the only objects launched toward Mars. NASA's Curiosity rover is the fifth robot to land on the surface of the Red Planet in the last 15 years. Pathfinder, Phoenix, Spirit and Opportunity all took detailed measurements of the planet; all but Phoenix traveled across the surface collecting a treasure trove of information.

The probes dug into the ground, examining rocks and performing experiments. In 2008, Phoenix turned up small chunks of bright material that disappeared after four days, leading scientists to surmise that they were pieces of water ice. The lander went on to detect water vapor in a sample it collected and analyzed, confirming the presence of frozen water on the red planet.

Spirit and Opportunity, the twin rovers, found traces of water enclosed in rock. In a shining example of a problem becoming a solution, a broken wheel on Spirit scraped into the top of the Martian surface, revealing a layer beneath rich in silica that had most likely formed in the presence of water.

Curiosity has found yet more evidence of water flowing on ancient Mars . The 1-ton rover rolled through an ancient stream bed shortly after touching down in August 2012, and it has examined a number of rocks that were exposed to liquid water billions of years ago. 

Mars missions aren't the only way to search for water on Mars. Scientists studying rocks ejected from the Red Planet found signs that water lay beneath the surface in the past.

"While robotic missions to Mars continue to shed light on the planet's history, the only samples from Mars available for study on Earth are Martian meteorites," lead author Lauren White, of the JPL, said in a statement .

"On Earth, we can utilize multiple analytical techniques to take a more in-depth look at meteorites and shed light on the history of Mars."

Historical landforms

In addition to examining the relatively recent (geologically speaking) presence of water, the various missions have also studied the surface of the planet in a historical context. The river beds of Mars don't run wet today, but scientists can study them to learn more about the evolution of the planet. [ Photos: The Search for Water on Mars ]

The flatter northern plains of Mars may once have hosted an ocean , or possibly, as the planet cycled through dry periods, two. The more recent body of water would likely have only been temporary, seeping into the ground, evaporating, or freezing in less than a million years, scientists say. 

Riverbeds and gullies indicate that water ran, at least briefly, across the surface of Mars. A hundred times more water may have flowed annually through a large channel system known as Marte Vallis than passes through the Mississippi River each year, according to estimates. The gullies themselves are smaller, likely forming during brief torrential rainstorms when fast-moving water could have carved them across the land.

Curiosity found indications that at least one region of Mars, Mount Sharp, was built by sediments deposited in a lake bed millions of years ago, suggesting large pools existed on the planet for significant time periods.

"If our hypothesis for Mount Sharp holds up, it challenges the notion that warm and wet conditions were transient, local, or only underground on Mars," Curiosity deputy project scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory (JPL) said in a statement .

On Earth, the land around rivers and lakes is wetter, made up of mud and clays . Such deposits exist on Mars as well, trapping water and indicating where larger bodies may have once existed.

Water on Mars may be doing something more than sitting pretty. A new study reveals that when the liquid boils, thanks to low pressures, it can make the sand levitate.

"Sediment levitation must therefore be considered when evaluating the formation of recent and present-day Martian mass wasting features, as much less water may be required to form such features than previously thought," the researchers wrote in their study, which was published in the journal Nature Communications .

Liquid gold

Water may seem like a very common element to those of us stuck on Earth, but it has great value. In addition to understanding how Mars may have changed and developed over time, scientists hope that finding water will help them to find something even more valuable — life, either past or present.

Only Earth is known to host life, and life on our planet requires water. Though life could conceivably evolve without relying on this precious liquid, scientists can only work with what they know. Thus they hope that locating water on celestial bodies such as Mars will lead to finding evidence for life.

With this in mind, NASA developed a strategy for exploring the Red Planet that takes as its mantra "follow the water." Recent orbiters, landers and rovers sent to Mars were designed to search for water, rather than life, in the hopes of finding environments where life could have thrived.

That has changed, however, with the flood of evidence these robots have returned. Curiosity determined that Mars could indeed have supported microbial life in the ancient past, and the next NASA rover — a car-size robot based heavily on Curiosity's basic design — will blast off in 2020 to look for evidence of past Red Planet life.

Additional resources

• Phoenix Mars Mission: Summary of Water on Mars
• NASA's "Follow the Water" Strategy
• NASA and the Case of the Missing Mars Water

Follow Nola Taylor Redd at @NolaTRedd , Facebook or Google+ . Follow us at @Spacedotcom , Facebook or Google+ . 

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Nola Taylor Tillman is a contributing writer for Space.com. She loves all things space and astronomy-related, and enjoys the opportunity to learn more. She has a Bachelor’s degree in English and Astrophysics from Agnes Scott college and served as an intern at Sky & Telescope magazine. In her free time, she homeschools her four children. Follow her on Twitter at @NolaTRedd

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Nasa confirms evidence that liquid water flows on today’s mars.

Editor’s note: The findings described in this press release were updated with additional research published on Nov. 20, 2017, and described in ” Recurring Martian Streaks: Sand, not Water ?”

New findings from NASA’s Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.

Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.

“Our quest on Mars has been to ‘follow the water,’ in our search for life in the universe, and now we have convincing science that validates what we’ve long suspected,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “This is a significant development, as it appears to confirm that water — albeit briny — is flowing today on the surface of Mars.”

These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it’s likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.

“We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks,” said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.

Ojha first noticed these puzzling features as a University of Arizona undergraduate student in 2010, using images from the MRO’s High Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).

The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren’t as extensive, they detected no hydrated salt.  

Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.

Perchlorates have previously been seen on Mars. NASA’s Phoenix lander and Curiosity rover both found them in the planet’s soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.

MRO has been examining Mars since 2006 with its six science instruments.

“The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are,” said Rich Zurek, MRO project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.

“When most people talk about water on Mars, they’re usually talking about ancient water or frozen water,” he said. “Now we know there’s more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL.”

The discovery is the latest of many breakthroughs by NASA’s Mars missions.

“It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program at the agency’s headquarters in Washington. “It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future.” 

There are eight co-authors of the Nature Geoscience paper, including Mary Beth Wilhelm at NASA’s Ames Research Center in Moffett Field, California and Georgia Tech; CRISM Principal Investigator Scott Murchie of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland; and HiRISE Principal Investigator Alfred McEwen of the University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona. Others are at Georgia Tech, the Southwest Research Institute in Boulder, Colorado, and Laboratoire de Planétologie et Géodynamique in Nantes, France.

The agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California manages the Mars Reconnaissance Orbiter Project for NASA’s Science Mission Directorate, Washington. Lockheed Martin built the orbiter and collaborates with JPL to operate it.

More information about NASA’s journey to Mars is available online at:

For more information about the Mars Reconnaissance Orbiter, visit:

https://www.nasa.gov/mro

Dwayne Brown / Laurie Cantillo Headquarters, Washington 202-358-1726 / 202-358-1077 [email protected] / [email protected] Guy Webster Jet Propulsion Laboratory, Pasadena, Calif. 818-354-6278 [email protected]

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Mars Had Liquid Water On Its Surface. Here's Why Scientists Think It Vanished

Scott Neuman

A close-up of Mars taken by NASA's Hubble Space Telescope. New research suggests that the red planet may be too small to have ever had large amounts of surface water. NASA/WireImage hide caption

A close-up of Mars taken by NASA's Hubble Space Telescope. New research suggests that the red planet may be too small to have ever had large amounts of surface water.

All evidence points to the fact that Mars once had flowing water, but numerous flybys, orbiters, landers and rovers have confirmed one undeniable fact — any liquid water that was once on its surface is now long gone.

A study out of Washington University in St. Louis might have found the reason: Mars, which is about half the size of Earth, and just over one-tenth the mass of our own watery world, might just be too small.

Water, Water, Every Where — And Now Scientists Know Where It Came From

One idea, the Mars Ocean Hypothesis , suggests that Mars not only had some liquid water, but a lot of it. But the new study's co-author Kun Wang says his team's finding, which was published this week in the Proceedings of the National Academy of Sciences, pours cold water on that notion.

"Mars' fate was decided from the beginning," Wang, an assistant professor of Earth and planetary sciences, said in a statement. "There is likely a threshold on the size requirements of rocky planets to retain enough water to enable habitability and plate tectonics."

That's because the lower mass and gravity of Mars makes it easier for volatile elements and compounds such as water to escape from its surface into space.

Led by Zhen Tian, a graduate student in Wang's laboratory, the researchers looked at 20 Martian meteorites ranging in age from about 200 million years old to 4 billion years, dating to a time when the solar system was still in the chaos of formation.

The researchers analyzed a somewhat volatile element — potassium — to help understand how water would have behaved on the surface of Mars.

Speaking to NPR, Wang said the team measured the ratio of two isotopes of potassium — potassium-39 and potassium-41 — in the meteorites. In lower gravity environments, such as Mars, the potassium-39 is more easily lost to space, leaving behind a higher ratio of the heavier isotope, potassium-41. Water behaves in much the same way, indicating that most of it would have been lost to space during the formation of Mars.

It's something Wang and his colleagues saw even in the oldest meteorites, suggesting that this was an issue for Martian water right from the beginning.

The team also looked at samples from the moon and from an asteroid, both much smaller and drier than either Earth or Mars, to study the potassium isotopes in them. They found a direct correlation between mass and the volatiles — or lack thereof — in the samples.

The liquid water that did remain on the Martian surface carved out the now-desiccated canyons, riverbeds and other formations that we see there today, Wang says. But that water, too, would likely have disappeared had it not been trapped as ice at the Martian poles as the climate on the planet became colder, he notes.

The findings could help refine the search for habitable exoplanets

The research has implications outside of our solar system, too. As scientists hunt for planets around other stars, the holy grail of their quest is to find those capable of supporting life — which means neither too hot nor too cold.

Even if a planet orbits its star in the so-called Goldilocks Zone, at just the right distance to be warm enough for liquid water without being too hot to support life, it could still be too small to keep hold of the water.

"This does probably indicate a lower limit on size for a planet to be truly habitable," Bruce Macintosh, deputy director of Stanford University's Kavli Institute for Particle Physics and Cosmology, tells NPR. "Understanding that lower limit is important — there are lines of evidence that small planets are more common than big ones, so if the small ones are dry, then there are fewer potentially habitable worlds out there than we thought."

He adds, however, that only "the most optimistic exoplanet astronomers" would currently list a Mars-size exoplanet as a candidate for habitability.

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Earthlike Planets: Venus and Mars

Water and life on mars, learning objectives.

By the end of this section, you will be able to:

• Describe the general composition of the atmosphere on Mars
• Explain what we know about the polar ice caps on Mars and how we know it
• Describe the evidence for the presence of water in the past history of Mars
• Summarize the evidence for and against the possibility of life on Mars

Of all the planets and moons in the solar system, Mars seems to be the most promising place to look for life, both fossil microbes and (we hope) some forms of life deeper underground that still survive today. But where (and how) should we look for life? We know that the one requirement shared by all life on Earth is liquid water. Therefore, the guiding principle in assessing habitability on Mars and elsewhere has been to “follow the water.” That is the perspective we take in this section, to follow the water on the red planet and hope it will lead us to life.

Atmosphere and Clouds on Mars

The atmosphere of Mars today has an average surface pressure of only 0.007 bar, less than 1% that of Earth. (This is how thin the air is about 30 kilometers above Earth’s surface.) Martian air is composed primarily of carbon dioxide (95%), with about 3% nitrogen and 2% argon. The proportions of different gases are similar to those in the atmosphere of Venus (see [link] ), but a lot less of each gas is found in the thin air on Mars.

While winds on Mars can reach high speeds, they exert much less force than wind of the same velocity would on Earth because the atmosphere is so thin. The wind is able, however, to loft very fine dust particles, which can sometimes develop planet-wide dust storms. It is this fine dust that coats almost all the surface, giving Mars its distinctive red color. In the absence of surface water, wind erosion plays a major role in sculpting the martian surface ( [link] ).

The issue of how strong the winds on Mars can be plays a big role in the 2015 hit movie The Martian in which the main character is stranded on Mars after being buried in the sand in a windstorm so great that his fellow astronauts have to leave the planet so their ship is not damaged. Astronomers have noted that the martian winds could not possibly be as forceful as depicted in the film. In most ways, however, the depiction of Mars in this movie is remarkably accurate.

Although the atmosphere contains small amounts of water vapor and occasional clouds of water ice, liquid water is not stable under present conditions on Mars. Part of the problem is the low temperatures on the planet. But even if the temperature on a sunny summer day rises above the freezing point, the low pressure means that liquid water still cannot exist on the surface, except at the lowest elevations. At a pressure of less than 0.006 bar, the boiling point is as low or lower than the freezing point, and water changes directly from solid to vapor without an intermediate liquid state (as does “dry ice,” carbon dioxide, on Earth). However, salts dissolved in water lower its freezing point, as we know from the way salt is used to thaw roads after snow and ice forms during winter on Earth. Salty water is therefore sometimes able to exist in liquid form on the martian surface, under the right conditions.

Several types of clouds can form in the martian atmosphere. First there are dust clouds, discussed above. Second are water-ice clouds similar to those on Earth. These often form around mountains, just as happens on our planet. Finally, the CO 2 of the atmosphere can itself condense at high altitudes to form hazes of dry ice crystals. The CO 2 clouds have no counterpart on Earth, since on our planet temperatures never drop low enough (down to about 150 K or about 125 °C) for this gas to condense.

The Polar Caps

Through a telescope, the most prominent surface features on Mars are the bright polar caps, which change with the seasons, similar to the seasonal snow cover on Earth. We do not usually think of the winter snow in northern latitudes as a part of our polar caps, but seen from space, the thin winter snow merges with Earth’s thick, permanent ice caps to create an impression much like that seen on Mars ( [link] ).

The seasonal caps on Mars are composed not of ordinary snow but of frozen CO 2 (dry ice). These deposits condense directly from the atmosphere when the surface temperature drops below about 150 K. The caps develop during the cold martian winters and extend down to about 50° latitude by the start of spring.

Quite distinct from these thin seasonal caps of CO 2 are the permanent or residual caps that are always present near the poles. The southern permanent cap has a diameter of 350 kilometers and is composed of frozen CO 2 deposits together with a great deal of water ice. Throughout the southern summer, it remains at the freezing point of CO 2 , 150 K, and this cold reservoir is thick enough to survive the summer heat intact.

The northern permanent cap is different. It is much larger, never shrinking to a diameter less than 1000 kilometers, and is composed of water ice. Summer temperatures in the north are too high for the frozen CO 2 to be retained. Measurements from the Mars Global Surveyor have established the exact elevations in the north polar region of Mars, showing that it is a large basin about the size of our own Arctic Ocean basin. The ice cap itself is about 3 kilometers thick, with a total volume of about 10 million km 3 (similar to that of Earth’s Mediterranean Sea). If Mars ever had extensive liquid water, this north polar basin would have contained a shallow sea. There is some indication of ancient shorelines visible, but better images will be required to verify this suggestion.

Images taken from orbit also show a distinctive type of terrain surrounding the permanent polar caps, as shown in [link] . At latitudes above 80° in both hemispheres, the surface consists of recent layered deposits that cover the older cratered ground below. Individual layers are typically ten to a few tens of meters thick, marked by alternating light and dark bands of sediment. Probably the material in the polar deposits includes dust carried by wind from the equatorial regions of Mars.

What do these terraced layers tell us about Mars? Some cyclic process is depositing dust and ice over periods of time. The time scales represented by the polar layers are tens of thousands of years. Apparently the martian climate experiences periodic changes at intervals similar to those between ice ages on Earth. Calculations indicate that the causes are probably also similar: the gravitational pull of the other planets produces variations in Mars’ orbit and tilt as the great clockwork of the solar system goes through its paces.

The Phoenix spacecraft landed near the north polar cap in summer ( [link] ). Controllers knew that is would not be able to survive a polar winter, but directly measuring the characteristics of the polar region was deemed important enough to send a dedicated mission. The most exciting discovery came when the spacecraft tried to dig a shallow trench under the spacecraft. When the overlying dust was stripped off, they saw bright white material, apparently some kind of ice. From the way this ice sublimated over the next few days, it was clear that it was frozen water.

Comparing the Amount of Water on Mars and Earth It is interesting to estimate the amount of water (in the form of ice) on Mars and to compare this with the amount of water on Earth. In each case, we can find the total volume of a layer on a sphere by multiplying the area of the sphere (4π R 2 ) by the thickness of the layer. For Earth, the ocean water is equivalent to a layer 3 km thick spread over the entire planet, and the radius of Earth is 6.378 × 10 6 m (see Appendix F ). For Mars, most of the water we are sure of is in the form of ice near the poles. We can calculate the amount of ice in one of the residual polar caps if it is (for example) 2 km thick and has a radius of 400 km (the area of a circle is π R 2 ).

Solution The volume of Earth’s water is therefore the area 4π R 2

multiplied by the thickness of 3000 m:

This gives 1.5 × 10 18 m 3 of water. Since water has a density of 1 ton per cubic meter (1000 kg/m 3 ), we can calculate the mass:

For Mars, the ice doesn’t cover the whole planet, only the caps; the polar cap area is

(Note that we converted kilometers to meters.)

The volume = area × height, so we have:

Therefore, the mass is:

This is about 0.1% that of Earth’s oceans.

Check Your Learning A better comparison might be to compare the amount of ice in the Mars polar ice caps to the amount of ice in the Greenland ice sheet on Earth, which has been estimated as 2.85 × 10 15 m 3 . How does this compare with the ice on Mars?

The Greenland ice sheet has about 2.85 times as much ice as in the polar ice caps on Mars. They are about the same to the nearest power of 10.

Channels and Gullies on Mars

Although no bodies of liquid water exist on Mars today, evidence has accumulated that rivers flowed on the red planet long ago. Two kinds of geological features appear to be remnants of ancient watercourses, while a third class—smaller gullies—suggests intermittent outbreaks of liquid water even today. We will examine each of these features in turn.

In the highland equatorial plains, there are multitudes of small, sinuous (twisting) channels—typically a few meters deep, some tens of meters wide, and perhaps 10 or 20 kilometers long ( [link] ). They are called runoff channels because they look like what geologists would expect from the surface runoff of ancient rain storms. These runoff channels seem to be telling us that the planet had a very different climate long ago. To estimate the age of these channels, we look at the cratering record. Crater counts show that this part of the planet is more cratered than the lunar maria but less cratered than the lunar highlands. Thus, the runoff channels are probably older than the lunar maria, presumably about 4 billion years old.

The second set of water-related features we see are outflow channels ( [link] ) are much larger than the runoff channels. The largest of these, which drain into the Chryse basin where Pathfinder landed, are 10 kilometers or more wide and hundreds of kilometers long. Many features of these outflow channels have convinced geologists that they were carved by huge volumes of running water, far too great to be produced by ordinary rainfall. Where could such floodwater have come from on Mars?

As far we can tell, the regions where the outflow channels originate contained abundant water frozen in the soil as permafrost. Some local source of heating must have released this water, leading to a period of rapid and catastrophic flooding. Perhaps this heating was associated with the formation of the volcanic plains on Mars, which date back to roughly the same time as the outflow channels.

Note that neither the runoff channels nor the outflow channels are wide enough to be visible from Earth, nor do they follow straight lines. They could not have been the “canals” Percival Lowell imagined seeing on the red planet.

The third type of water feature, the smaller gullies , was discovered by the Mars Global Surveyor ( [link] ). The Mars Global Surveyor’s camera images achieved a resolution of a few meters, good enough to see something as small as a truck or bus on the surface. On the steep walls of valleys and craters at high latitudes, there are many erosional features that look like gullies carved by flowing water. These gullies are very young: not only are there no superimposed impact craters, but in some instances, the gullies seem to cut across recent wind-deposited dunes. Perhaps there is liquid water underground that can occasionally break out to produce short-lived surface flows before the water can freeze or evaporate.

The gullies also have the remarkable property of changing regularly with the martian seasons. Many of the dark streaks (visible in [link] ) elongate within a period of a few days, indicating that something is flowing downhill—either water or dark sediment. If it is water, it requires a continuing source, either from the atmosphere or from springs that tap underground water layers (aquifers.) Underground water would be the most exciting possibility, but this explanation seems inconsistent with the fact that many of the dark streaks start at high elevations on the walls of craters.

Additional evidence that the dark streaks (called by the scientists recurring slope lineae ) are caused by water was found in 2015 when spectra were obtained of the dark streaks ( [link] ). These showed the presence of hydrated salts produced by the evaporation of salty water. If the water is salty, it could remain liquid long enough to flow downstream for distances of a hundred meters or more, before it either evaporates or soaks into the ground. However, this discovery still does not identify the ultimate source of the water.

Ancient Lakes

The rovers ( Spirit , Opportunity , and Curiosity ) that have operated on the surface of Mars have been used to hunt for additional evidence of water. They could not reach the most interesting sites, such as the gullies, which are located on steep slopes. Instead, they explored sites that might be dried-out lake beds, dating back to a time when the climate on Mars was warmer and the atmosphere thicker—allowing water to be liquid on the surface.

Spirit was specifically targeted to explore what looked like an ancient lake-bed in Gusev crater, with an outflow channel emptying into it. However, when the spacecraft landed, it found that the former lakebed had been covered by thin lava flows, blocking the rover from access to the sedimentary rocks it had hoped to find. However, Opportunity had better luck. Peering at the walls of a small crater, it detected layered sedimentary rock. These rocks contained chemical evidence of evaporation, suggesting there had been a shallow salty lake in that location. In these sedimentary rocks were also small spheres that were rich in the mineral hematite, which forms only in watery environments. Apparently this very large basin had once been underwater.

The small spherical rocks were nicknamed “blueberries” by the science team and the discovery of a whole “berry-bowl” of them was announced in this interesting news release from NASA.

The Curiosity rover landed inside Gale crater, where photos taken from orbit also suggested past water erosion. It discovered numerous sedimentary rocks, some in the form of mudstones from an ancient lakebed; it also found indications of rocks formed by the action of shallow water at the time the sediment formed ( [link] ).

People like human faces. We humans have developed great skill in recognizing people and interpreting facial expressions. We also have a tendency to see faces in many natural formations, from clouds to the man in the Moon. One of the curiosities that emerged from the Viking orbiters’ global mapping of Mars was the discovery of a strangely shaped mesa in the Cydonia region that resembled a human face. Despite later rumors of a cover-up, the “Face on Mars” was, in fact, recognized by Viking scientists and included in one of the early mission press releases. At the low resolution and oblique lighting under which the Viking image was obtained, the mile-wide mesa had something of a Sphinx-like appearance.

Unfortunately, a small band of individuals decided that this formation was an artificial, carved sculpture of a human face placed on Mars by an ancient civilization that thrived there hundreds of thousands of years ago. A band of “true believers” grew around the face and tried to deduce the nature of the “sculptors” who made it. This group also linked the face to a variety of other pseudoscientific phenomena such as crop circles (patterns in fields of grain, mostly in Britain, now known to be the work of pranksters).

Members of this group accused NASA of covering up evidence of intelligent life on Mars, and they received a great deal of help in publicizing their perspective from tabloid media. Some of the believers picketed the Jet Propulsion Laboratory at the time of the failure of the Mars Observer spacecraft, circulating stories that the “failure” of the Mars Observer was itself a fake, and that its true (secret) mission was to photograph the face.

The high-resolution Mars Observer camera (MOC) was reflown on the Mars Global Surveyor mission, which arrived at Mars in 1997. On April 5, 1998, in Orbit 220, the MOC obtained an oblique image of the face at a resolution of 4 meters per pixel, a factor-of-10 improvement in resolution over the Viking image. Another image in 2001 had even higher resolution. Immediately released by NASA, the new images showed a low mesa-like hill cut crossways by several roughly linear ridges and depressions, which were misidentified in the 1976 photo as the eyes and mouth of a face. Only with an enormous dose of imagination can any resemblance to a face be seen in the new images, demonstrating how dramatically our interpretation of geology can change with large improvements in resolution. The original and the higher resolution images can be seen in [link] .

After 20 years of promoting pseudoscientific interpretations and various conspiracy theories, can the “Face on Mars” believers now accept reality? Unfortunately, it does not seem so. They have accused NASA of faking the new picture. They also suggest that the secret mission of the Mars Observer included a nuclear bomb used to destroy the face before it could be photographed in greater detail by the Mars Global Surveyor .

Space scientists find these suggestions incredible. NASA is spending increasing sums for research on life in the universe, and a major objective of current and upcoming Mars missions is to search for evidence of past microbial life on Mars. Conclusive evidence of extraterrestrial life would be one of the great discoveries of science and incidentally might well lead to increased funding for NASA. The idea that NASA or other government agencies would (or could) mount a conspiracy to suppress such welcome evidence is truly bizarre.

Alas, the “Face on Mars” story is only one example of a whole series of conspiracy theories that are kept before the public by dedicated believers, by people out to make a fast buck, and by irresponsible media attention. Others include the “urban legend” that the Air Force has the bodies of extraterrestrials at a secret base, the widely circulated report that UFOs crashed near Roswell, New Mexico (actually it was a balloon carrying scientific instruments to find evidence of Soviet nuclear tests), or the notion that alien astronauts helped build the Egyptian pyramids and many other ancient monuments because our ancestors were too stupid to do it alone.

In response to the increase in publicity given to these “fiction science” ideas, a group of scientists, educators, scholars, and magicians (who know a good hoax when they see one) have formed the Committee for Skeptical Inquiry. Two of the original authors of your book are active on the committee. For more information about its work delving into the rational explanations for paranormal claims, see their excellent magazine, The Skeptical Inquirer , or check out their website at www.csicop.org/.

Climate Change on Mars

The evidence about ancient rivers and lakes of water on Mars discussed so far suggests that, billions of years ago, martian temperatures must have been warmer and the atmosphere must have been more substantial than it is today. But what could have changed the climate on Mars so dramatically?

We presume that, like Earth and Venus, Mars probably formed with a higher surface temperature thanks to the greenhouse effect. But Mars is a smaller planet, and its lower gravity means that atmospheric gases could escape more easily than from Earth and Venus. As more and more of the atmosphere escaped into space, the temperature on the surface gradually fell.

Eventually Mars became so cold that most of the water froze out of the atmosphere, further reducing its ability to retain heat. The planet experienced a sort of runaway refrigerator effect , just the opposite of the runaway greenhouse effect that occurred on Venus. Probably, this loss of atmosphere took place within less than a billion years after Mars formed. The result is the cold, dry Mars we see today.

Conditions a few meters below the martian surface, however, may be much different. There, liquid water (especially salty water) might persist, kept warm by the internal heat of Mars or the insulating layers solid and rock. Even on the surface, there may be ways to change the martian atmosphere temporarily.

Mars is likely to experience long-term climate cycles, which may be caused by the changing orbit and tilt of the planet. At times, one or both of the polar caps might melt, releasing a great deal of water vapor into the atmosphere. Perhaps an occasional impact by a comet might produce a temporary atmosphere that is thick enough to permit liquid water on the surface for a few weeks or months. Some have even suggested that future technology might allow us to terraform Mars—that is, to engineer its atmosphere and climate in ways that might make the planet more hospitable for long-term human habitation.

The Search for Life on Mars

If there was running water on Mars in the past, perhaps there was life as well. Could life, in some form, remain in the martian soil today? Testing this possibility, however unlikely, was one of the primary objectives of the Viking landers in 1976. These landers carried miniature biological laboratories to test for microorganisms in the martian soil. Martian soil was scooped up by the spacecraft’s long arm and placed into the experimental chambers, where it was isolated and incubated in contact with a variety of gases, radioactive isotopes, and nutrients to see what would happen. The experiments looked for evidence of respiration by living animals, absorption of nutrients offered to organisms that might be present, and an exchange of gases between the soil and its surroundings for any reason whatsoever. A fourth instrument pulverized the soil and analyzed it carefully to determine what organic (carbon-bearing) material it contained.

The Viking experiments were so sensitive that, had one of the spacecraft landed anywhere on Earth (with the possible exception of Antarctica), it would easily have detected life. But, to the disappointment of many scientists and members of the public, no life was detected on Mars. The soil tests for absorption of nutrients and gas exchange did show some activity, but this was most likely caused by chemical reactions that began as water was added to the soil and had nothing to do with life. In fact, these experiments showed that martian soil seems much more chemically active than terrestrial soils because of its exposure to solar ultraviolet radiation (since Mars has no ozone layer).

The organic chemistry experiment showed no trace of organic material, which is apparently destroyed on the martian surface by the sterilizing effect of this ultraviolet light. While the possibility of life on the surface has not been eliminated, most experts consider it negligible. Although Mars has the most earthlike environment of any planet in the solar system, the sad fact is that nobody seems to be home today, at least on the surface.

However, there is no reason to think that life could not have begun on Mars about 4 billion years ago, at the same time it started on Earth. The two planets had very similar surface conditions then. Thus, the attention of scientists has shifted to the search for fossil life on Mars. One of the primary questions to be addressed by future spacecraft is whether Mars once supported its own life forms and, if so, how this martian life compared with that on our own planet. Future missions will include the return of martian samples selected from sedimentary rocks at sites that once held water and thus perhaps ancient life. The most powerful searches for martian life (past or present) will thus be carried out in our laboratories here on Earth.

When scientists begin to search for life on another planet, they must make sure that we do not contaminate the other world with life carried from Earth. At the very beginning of spacecraft exploration on Mars, an international agreement specified that all landers were to be carefully sterilized to avoid accidentally transplanting terrestrial microbes to Mars. In the case of Viking, we know the sterilization was successful. Viking’s failure to detect martian organisms also implies that these experiments did not detect hitchhiking terrestrial microbes.

As we have learned more about the harsh conditions on the martian surface, the sterilization requirements have been somewhat relaxed. It is evident that no terrestrial microbes could grow on the martian surface, with its low temperature, absence of water, and intense ultraviolet radiation. Microbes from Earth might survive in a dormant, dried state, but they cannot grow and proliferate on Mars.

The problem of contaminating Mars will become more serious, however, as we begin to search for life below the surface, where temperatures are higher and no ultraviolet light penetrates. The situation will be even more daunting if we consider human flights to Mars. Any humans will carry with them a multitude of terrestrial microbes of all kinds, and it is hard to imagine how we can effectively keep the two biospheres isolated from each other if Mars has indigenous life. Perhaps the best situation could be one in which the two life-forms are so different that each is effectively invisible to the other—not recognized on a chemical level as living or as potential food.

The most immediate issue of public concern is not with the contamination of Mars but with any dangers associated with returning Mars samples to Earth. NASA is committed to the complete biological isolation of returned samples until they are demonstrated to be safe. Even though the chances of contamination are extremely low, it is better to be safe than sorry.

Most likely there is no danger, even if there is life on Mars and alien microbes hitch a ride to Earth inside some of the returned samples. In fact, Mars is sending samples to Earth all the time in the form of the Mars meteorites. Since some of these microbes (if they exist) could probably survive the trip to Earth inside their rocky home, we may have been exposed many times over to martian microbes. Either they do not interact with our terrestrial life, or in effect our planet has already been inoculated against such alien bugs.

More than any other planet, Mars has inspired science fiction writers over the years. You can find scientifically reasonable stories about Mars in a subject index of such stories online. If you click on Mars as a topic, you will find stories by a number of space scientists, including William Hartmann, Geoffrey Landis, and Ludek Pesek.

Key Concepts and Summary

The martian atmosphere has a surface pressure of less than 0.01 bar and is 95% CO 2 . It has dust clouds, water clouds, and carbon dioxide (dry ice) clouds. Liquid water on the surface is not possible today, but there is subsurface permafrost at high latitudes. Seasonal polar caps are made of dry ice; the northern residual cap is water ice, whereas the southern permanent ice cap is made predominantly of water ice with a covering of carbon dioxide ice. Evidence of a very different climate in the past is found in water erosion features: both runoff channels and outflow channels, the latter carved by catastrophic floods. Our rovers, exploring ancient lakebeds and places where sedimentary rock has formed, have found evidence for extensive surface water in the past. Even more exciting are the gullies that seem to show the presence of flowing salty water on the surface today, hinting at near-surface aquifers. The Viking landers searched for martian life in 1976, with negative results, but life might have flourished long ago. We have found evidence of water on Mars, but following the water has not yet led us to life on that planet.

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Water On Mars

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Mars has always held a special interest because of the possibility that life may have existed there, and its water history is crucial to understanding its geology, climatology, and biology. Moreover, recent studies in molecular phylogeny suggest that volcanic hot springs, which may have been common in early Mars, are also the most likely point of origin for life on Earth. In this book, Dr. Carr explores the history of water on Mars, including evidence that liquid water was once abundant at the planet’s surface; ways in which the climate might have changed to accommodate liquid water; and what an abundance of water implies for the formation of Mars and other planets, including Earth. The book’s argument rests on interpretation of data acquired on Viking missions, and on information from meteorites, found on Earth, that almost certainly originated on Mars. Because liquid water is universally regarded as essential for life, the water story has particular biological significance, with important implications for the future exploration of the planet, and should be a valuable study for geologists and planetary scientists.

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Observing the surface of the Red Planet allows scientists to assume that sometime in the planet’s early history—billions of years ago—it was covered with oceans, and had rivers flowing on its surface. It is considered that Mars was warm and moist enough to host life—not as we would like to imagine life on other planets, since most likely it was some sort of microbial life. However, the problem of the Red Planet is that its mass is lighter compared to Earth, which means its gravity was not strong enough to sustain the atmosphere. Gradually, the water evaporated into the atmosphere, and the atmosphere escaped into space, leaving Mars as the desolate desert we know today ( Space.com ).

There have been three more rover missions to Mars, including the latest: Curiosity-1 . One of their missions was to find evidence that the Red Planet had once been warmer and capable of supporting life. In 2014, the data collected by Curiosity assured scientists there had once been liquid water on Mars. In particular, the analysis of rocks at the bottom of Mount Sharp in the middle of Gale Crater—a 96-mile-wide barren bowl—has demonstrated rather intriguing results: judging from the alternating sediment layers at the base of the mountain, scientists assumed that over the course of millions of years, water flowed on Mars at different levels. Back then, Curiosity scientists suggested that Gale Crater was covered by a large ocean ( The Atlantic ).

The most revolutionary discovery, however, has been made just recently, on September 28, 2015. NASA has found absolute evidence that there is liquid water on Mars at present. NASA’s Mars Reconnaissance Orbiter identified the presence of perchlorates—hydrated minerals that have formed streaks on slopes on Mars’ surface. Perchlorates—at least some of them—are known to be able to keep water from freezing in extremely low temperatures; for example, -94 Fahrenheit, which is a temperature close to the average one on Mars, is not an obstacle for certain perchlorates to keep water from freezing. During the Mars “hot” seasons, when the temperature on the surface gets around -10 degrees Fahrenheit, perchlorates form streaks—also called recurring slope lineae—on the Martian surface. During the cold season, these lines usually disappear ( Wired.com ).

According to Lujendra Ojha, one of the project’s researchers, this gives scientists a clearer picture of what water is like on Mars. “Something is hydrating these salts, and it appears to be these streaks that come and go with the seasons. This means the water on Mars is briny, rather than pure. It makes sense, because salts lower the freezing point of water. Even if RSL are slightly underground, where it’s even colder than the surface temperature, the salts would keep the water in a liquid form and allow it to creep down Martian slopes.” Although their team has no clue about where the water comes from, they suggest it might be the underground ice melting, or subterranean streams feeding water to the surface (Wired.com).

Although the recent NASA discovery is not the long anticipated image of water freely flowing on the Martian surface, it has aided scientists in figuring out the truth about water on the Red Planet. Great scientific discoveries rarely look like something fabulous—remember the Newton’s apple, for example—but the form in which these discoveries are made rarely influence the greatness of their outcomes.

Fleur, Nicholas St. “The Evolving Search for Life on Mars.” The Atlantic. Atlantic Media Company, 15 Dec. 2014. Web. 29 Sept. 2015.

Redd, Nola Taylor. “Water on Mars: Exploration & Evidence.” Space.com. N.p., n.d. Web. 29 Sept. 2015.

“NASA Discovers Evidence for Liquid Water on Mars.” Wired.com. Conde Nast Digital, n.d. Web. 29 Sept. 2015.

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NASA Orbiter Provides Insights About Mars Water and Climate

NASA's Mars Reconnaissance Orbiter is examining several features on Mars that address the role of water at different times in Martian history.

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Mars: Water and the Martian Landscape Essay

According to McSween, scientists and astronomers find the study of the environment of Mars and the existence of flowing of water on the surface of the planet of special interest (1). McSween argues here that the evolution of any basic form of life depends on the existence of water. A deep water analogy of the existence of water in the atmosphere of Mars was based on the large scale polygonal terrains and other terrestrial elements on the surface of the planet, which makes Mars a viable candidate to study.

Mars, like the Earth, undergoes orbital oscillations which are caused by the behavior of the planet’s varying climatic conditions. Scientific evidence shows that the gravitational effects of other planets on Mars, particularly Jupiter, causes Mars to have an obliquity of 25.2 0 when compared with Earth’s obliquity of 23.5 0 (Clifford 1). Opponents of the existence of water in the atmosphere of Mars argue that the evidence that supports the existence of water in not scientifically conclusive.

Maheshwari argues that Mars’ gravitational force and its thin atmosphere cannot hold or retain water (3). It has been demonstrated that the weak strength of the gravity of Mars causes “subsurface porosity to a greater depth” to occur, supporting the argument that water cannot be found in the atmosphere of Mars (Clifford 6).

A further argument against the existence of water in the atmosphere of Mars is that the gullies and other geographical structures on the surface of the planet might have been caused by the movement of strong winds for millions of years. In addition, the average temperature on Mars is 60 K and ta that temperature liquid water cannot exist. Different authors further argue that the features observed on the surface of Mars were created by submarine terrestrial mass-transport deposits.

On the contrary, the presence of clay deposits, massive ridges, craters, and other subsurface characteristics support the positions that there might have existed large amounts of water in the atmosphere of Mars. Jakosky and Mellon refute the of the existence of water at one point in the history of Mars and assert that the Martian oscillations and the tilting of the planet towards the sun caused its polar ice caps to meltwater sublimates, which increased the global humidity during the early Noachian period (71).

Any slight changes in the obliquity of the planet dramatically changed the climate and the distribution of water-ice in the atmosphere. The presence of surface and sub-surface water-ice caused a significant amount of geomorphic changes to the environment, resulting in the type of climate variations depicted in the figure below (McSween 2).

The presence of ice-rich soils, variations in the climate, thermal stresses, and contractions led to the development of the features on the surface of Mars. That forms the basis of many years of scientific study and mapping of the surface of the planet, which has led to the conclusive evidence that liquid water, flowed in abundance on the surface of the planet (McSween 2).

Carr’s extensive discussions of scientific and unambiguous evidence of the flow of large amounts of water on the surface of the planet in the past were based on the geographic features and chemical compositions of the existing surface rocks (1). Carr’s report shows extensive channels consisting of polygonal features, small scale gullies, and valley networks on the surface of the planet, which was observed by a high-resolution spacecraft flying past Mars.

According to Carr, the observations include large terrestrial flood channels, cataracts, inner channels with diverging and converging score patterns, and plucked zones (2). The physical features shown below emphasize the existence of water 3.8 million years ago.

In a scientific conference held in 2014 to study additional evidence of the existence of water on the face of planet Mars millions of years ago, Arfstrom wrote about a network of channels observed on the surface of Mars as characteristic of the evidence of water (1).

Arfstrom’s channels are characterized by branching, and undulating elevated terminal deposition fans measuring 6 km wide and large scale streamlined landforms, as shown in the diagram below (3). Recent scientific findings of hematite, a substance associated with the presence of water, provide further evidence of a one-time presence of water in the atmosphere of Mars.

The two branches of streamlined landforms, which were the direct cause of erosion and selective large scale linear erosion consisting of sub-polar ice, converge at the end of the hill after a distance of 6 km. Observations and detailed investigations reveal striking features of sublimation pits presumed to be an icy mantle, which is assumed to have been caused by erosion (Clifford 2).

A clear illustration of the landscape caused by the flow of water is shown in the diagram below. After studying the evidence which shows the flow of water on the surface of the planet, the question arises on, where did the water go?

Where the water went

Conclusive evidence shows that millions of years ago, there was water on Mars. The assumption is based on geochemical evidence and a study of the oldest meteorites ALH84001 found on Mars. The meteorite is characterized by carbonates, which could have been deposited because of the presence of water 4 billion years ago.

A remote sensing study conducted by using MGS and Mars Odyssey to map the surface morphology of Mars shows further evidence of the effects of water. The question as to where the water went is still a mystery. The different hypothesis has been developed to answer the question of the disappearance of water from the planet Mars (McSween 2).

Today, there is no water in the atmosphere of Mars, and deep water levels that existed millions of years ago do not exist now. Scientific research has shown that water on the planet might have been lost because of the interactions between water molecules and solar winds, which broke the water molecules apart into hydrogen and oxygen molecules.

The molecules were later ionized and carried by the solar winds into the atmosphere (Stephen 2). Solar winds are plasma made of protons and electrons, which originate from the sun’s corona. Solar winds move radially from the sun at speeds of thousands of kilometers per hour (McSween 3).

When the wind enters the atmosphere of planets such as Mars with a low magnetic field, the solar wind interacts directly with any particles of the planet’s atmosphere setting up ionosphere currents, which deflect the planet’s magnetic fields around the planet. The resulting reactions between the neutral atoms and the solar winds cause drag in the speed of the solar wind, leading to the loss of the planet’s atmosphere (Maheshwari 1).

The ionized particles are then accelerated by the electric fields producing matter known as ENAs, which is composed of oxygen and hydrogen. Esther escapes from the atmosphere of the planet at high speeds. Here, the weak gravitational pull of the planet and the effects of solar winds are arguably the main causes of the loss of water into space (McSween 4).

The presence or absence of water could have significant scientific implications on scientific research, and the question that could be answered does the planet support life? One of the implications is that if water existed in the atmosphere of Mars, there could be the possibility of extraterrestrial life (Mcewen, 58).

It could show further that water exists in other planets and the possibility of different forms of life, other than the complex forms of life like on Earth, exist in those planets. It could be the beginning of the study of the evolution of life to understand how life forms evolve.

In conclusion, despite the overwhelming argument in favor of the fact that there is no water in Mars’ atmosphere which has never flowed on the surface, there is plenty of scientific evidence to show that water flowed on the surface of Mars millions of years ago.

The fundamental factors which caused the loss of water included weak gravitational strength coupled with the effects of solar winds. The crucial evidence is based on the surface landscape, the sublimation pits, ice at the Polar Regions, and other crucial features support the argument in favor of the presence of water in the atmosphere of Mars.

Works Cited

Arfstrom, John D. “ A Possible Tunnel Valley Network in East Kasei Valles, Mars .” 45th Lunar and Planetary Science Conference. The Woodlands, Texas. 17-21 2014. Web.

Carr, Michael H. Water on Mars . New York: Oxford University Press , 1996. Print.

Clifford, Stephen M. “A model for the hydrologic and climatic behavior of water on

Mars.” Journal of Geophysical Research: Planets 98. E6 (1993): 10973-11016. Print.

Jakosky, Bruce M., and Mellon, Michael T, “Water on Mars.” Physics Today 57.4

(2004): 71-76. Print.

Maheshwari, Raaz. “Water on Mars.” Bull. Env. Pharmacol. Life, Sci. 2.1 (2012): 01-02. Print.

Mcewen, Alfred S. “Mars in Motion.” Scientific American . 308.5 (2003): 58-65. Print.

McSween, Harry Y. “Water on Mars.” Elements 2.3 (2006): 135-137. Print.

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IvyPanda. (2022, May 2). Mars: Water and the Martian Landscape. https://ivypanda.com/essays/mars-environment/

"Mars: Water and the Martian Landscape." IvyPanda , 2 May 2022, ivypanda.com/essays/mars-environment/.

IvyPanda . (2022) 'Mars: Water and the Martian Landscape'. 2 May.

IvyPanda . 2022. "Mars: Water and the Martian Landscape." May 2, 2022. https://ivypanda.com/essays/mars-environment/.

1. IvyPanda . "Mars: Water and the Martian Landscape." May 2, 2022. https://ivypanda.com/essays/mars-environment/.

Bibliography

IvyPanda . "Mars: Water and the Martian Landscape." May 2, 2022. https://ivypanda.com/essays/mars-environment/.

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• Water on Mars

In many ways, Mars is the most Earthlike of all the planets. A visitor would find that a day on Mars is only slightly longer than one on Earth. Mars is also tilted about the same amount as the Earth, so it has seasons.

Both Mars and Earth have white polar caps. Those on Mars are much smaller and thinner, so they grow quickly in winter and almost disappear in summer. They are much colder than the polar caps on Earth, so they contain frozen carbon dioxide (the 'dry ice' used to create fog in stage shows) as well as water ice.

Mars is in the middle of an ice age, so liquid water cannot exist on its surface at the present time. However, the planet seems to have been warmer and wetter in the past.

Winding channels that look like dry river beds have been seen in spacecraft images. They suggest that huge amounts of water once flowed over the surface – possibly fed by melting ice. There may even have been rain and snow. Many of the channels seem to have filled large craters or emptied onto the northern plains. Some scientists believe there was a large ocean that covered the northern half of Mars.

Where did the water go? Some may have escaped into space. The rest is frozen in the ground.

More on Mars

• Life on Mars
• Mars' valleys and volcanoes
• Phobos and Deimos
• Mars - the red planet
• Radar’s icy echoes on Mars

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Abstract Water on Mars has been an on-going topic throughout planetary research and only recently has new evidence shown that it could be true in present day conditions. As technology advances, our knowledge on space exploration does also and technologies such as HiRISE, Curiosity and MRO have allowed us to gain an understanding of Mars that wouldn’t have been possible years ago. This report aims to bring together a small range of information about water on Mars from scientific research in an attempt to help the reader understand the progress. RSL, Curiosity, and mud cracks are few of the covered topics that have led scientists to believe liquid water is available on Mars and ultimately the potential for extra-terrestrial life. Introduction It was in 1659, when Dutch scientist Christian Huygens (1629-95), first identified a large dark blemish on the planet Mars, which has now been identified as Syrtis Major – a low-relief shield volcano (Hiesinger and Head, 2004). By recording series of data and photographic evidence over numerous weeks of changes in the spot, he was able to come to the conclusion that: a day on Mars was similar to that on Earth and Cassini (1625-1712) confirmed it was 37 minutes longer in 1666. A century later, William Herschel was able to prove that Mars rotated at an angle of approximately 25°, much similar to Earth (Crawford, 2013), indicating that like Earth, Mars had seasons as it orbited the Sun leading scientists to believe that they shared similar characteristics; one being Mars’ ability to retain liquid water and possibly sustain life. Consequently, this report will gather the past and present data regarding water on Mars and highlight the geological and geochemical evidence that suggests this idea. Method In order to write this report, secondary sources of information that were used were websites (NASA, Space.com) for up-to-date material, scientific journals written by specialists in the subject and news articles e.g. The New York. To ensure an accurate representation of known information, reliable sources were chosen such as those from public sector organisations as the data and material provided is regularly updated and government controlled ensuring reliability. Results Previous research led scientists to believe that liquid water was once abundant on the Martian planet as they discovered physical and chemical evidence through images taken by the Mars Reconnaissance Orbiter (Redd, 2015). This new evidence also allowed verification of geological formations such as RSL, mud cracks and ancient waterbeds and chemical indications of hydrated salt deposits. Recurring Slope Lineae On September 28, 2015, it was announced that an imaging spectrometer on MRO had detected images of downhill streaks (Runyon and Ojha, 2014) on the surface named Recurring Slope Lineae. (NASA, 2015). RSL are narrow surface markings, up to 5m wide, that are typically darker than the surrounding ground and were previously reported in southern middle latitudes (McEwen et al. 2013) but now known to be plentiful in equatorial areas such as Valles Marineris. These linear patterns seemed to appear during the warmer spring and summer seasons (Choi, 2011) and are believed to be the remnants of flowing liquid water. This suggests that water is present, as the rock remains the same colour, with a change in brightness as when water is in contact with sand on Earth. Mud cracks and hydrated minerals With new technologies such as HiRISE, scientists are able to obtain more information than ever before on the surface of Mars. Images of polygonal mud cracks were detected on the surface similar to those found on riverbeds here on Earth: this suggests large expanses of water such as oceans. The cracks were initially thought to be the result of thermal contractions in permafrost; however, the size was far too large to have been caused by this at 70-140 meters in diameter (Space.com, 2009), whereas thermal contractions are usually approximately 65 meters. Furthermore, remains of hydrated salts were found which, is a clear indication of the previous existence of water on Mars. Perchlorates Perchlorates are hydrated minerals left behind after expanses of briny water dry up (Chang, 2015). It was found that the minerals on Mars were made up of mostly magnesium perchlorate, magnesium chlorate and sodium chlorate (CRISM, 2015). Curiosity rover picked up traces of perchlorates in Gale Crater in 2012 (Jet Propulsion Laboratory, NASA, n.d.) previously and these perchlorates have been identified to resist the freezing of liquids at temperatures as low as -70°C. The presence of perchlorates has positive and negative impacts: it is a good thing as it suggests evidence of water and has been discovered to be a source of oxygen but it also has consequences as the percentage on Mars is between 0.5-1% which is toxic for astronauts (Carrier and Kounaves, 2015). Discussion From the research carried out, it is gathered that evidence of pre-existing liquid water is unmistakable and using newly found evidence (RSL); it could suggest that the water runs on Mars even today. The recurring slope lineae have no other explanation as to what caused them and without knowing the topography of the planet, as even HiRISE isn’t able to detect it, it is a good hypothesis to suggest liquid water as the creator. The mud cracks are clear evidence of former lakes and oceans and mimic those on Earth with similar characteristics and features. The perchlorates can be interpreted in different ways but in a broader context, they could only have formed by liquid transportation of salts i.e. briny liquid flowing water. These factors all point to remnants of water on Mars. Conclusion This information gives us an insight on the planet and helps us determine whether or not there is life on mars. It is a fact that water is needed to sustain life on a planet and if found on Mars, scientists believe it could link to life on the planet. However, the RSL have yet to prove that it is actual flowing water as it would either boil rapidly or absorb into the soil and freeze, so one would have to witness it happening to undoubtedly say that it was liquid. Currently, only the evidence of water being present has been suggested and no actual water found – be this because of technology not being advanced enough to apprehend this data or simply because it no longer exists. It is almost certain that a billion years ago water on Mars was plentiful as seen from ancient lakes and waterbeds but whether there remains liquid water today is the true question.

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Wish you were here? A composite picture taken by the Curiosity rover’s Navcams in both morning and afternoon light, 16 November 2021. Photo by NASA

Thriving on Mars

Dust storms, long distances and freezing temperatures make living on mars magnificently challenging. how will we do it.

by Simon Morden   + BIO

Can humans live on Mars? The answer is startlingly simple. Can humans live in Antarctica, where the temperatures regularly fall below -50ºC (-60ºF) and it’s dark for six months of the year? Can humans live below the ocean, where pressure rapidly increases with depth to crushing levels? Can humans live in space, where there’s no air at all?

As the limits of our ingenuity, our materials science and our chemistry have grown, we’ve gone from being able to tolerate only a narrow band of conditions to expanding our presence to almost every part of the globe, and now beyond it. Even the most hostile environment we’ve ever faced – the vacuum of space – has had a continuous human population for more than two decades.

So why not Mars? If we can live in Antarctica, if we can live in space, then surely it’s simply a question of logistics. If we can put enough materiel on the surface of the Red Planet, then perhaps we can survive – and even thrive – there.

But that ‘if’ is doing an awful lot of work. When we went to the Moon, the astronauts had to carry everything for their visit in their tiny, fragile landers. The Apollo missions spent between just one and three days on the surface – and it took only three days to get to the Moon itself. When a Mars-bound astronaut will spend months in space just getting to the landing spot, spending just a couple of days on the planet isn’t going to satisfy. Any mission, even the initial one, will necessarily be planned to be months-long, and that increases the complexity of the logistics enormously.

M ars is a particularly difficult planet to land on . It’s too far away from Earth to control any descent remotely – on average, a radio signal takes 12 minutes to cover the distance – so everything has to be preprogrammed in. A single error in either the computer or in its inputs will result in a new and expensive crater, of which there’ve been many. And once the command for landing has been given, there’s nothing that anyone back in Mission Control can do to intervene – the length of time it takes between that order, and a safe landing , is known as the ‘seven minutes of terror’.

The tenuous Martian atmosphere also complicates landing. It’s thick enough that any deorbiting spacecraft requires a heatshield to prevent it from burning up, but even the latest generation of vast, supersonic-rated parachutes struggles to provide significant purchase on the tenuous air on the way down. What remains of the orbit velocity has to be accounted for, or our landers will break against the frozen Martian surface.

A vast silver rocket with everything the astronauts need for their months-long stay simply isn’t practical

Various methods have been used, but the most consistently successful has been the ‘sky crane’, a disposable frame fitted with retro-rockets that burn until it’s hovering a few yards above the surface. It then winches the lander down gently, disengages its connecting cables, and then flies a safe distance away before its propellent runs out.

As expected, these calculations are very finely judged. Every pound of lander – the batteries, the solar panels, the scientific experiments – needs several kilogrammes of fuel in the sky crane. And every kilogramme of fuel in the sky crane requires several more kilogrammes of fuel on the rocket that takes it to Mars orbit. We’d send bigger, better landers to Mars if we could – but rocketry is at the very limits of our capabilities, getting a rover the size of a subcompact down to the ground. This has huge implications for conducting a successful crewed mission to Mars.

While we might dream of a vast silver rocket slowly descending to the dusty red surface, containing everything that the astronauts need for their months-long stay, we have to realise that it simply isn’t practical. That rocket, and the even-larger spaceship required to get it there, is beyond our projected launch capabilities for decades, if not centuries, to come. Planning for a successful Mars mission – for a permanent presence on Mars – requires us to work smarter , and use every advantage that we can. That includes those we can find on Mars itself.

M ars is a planet full of useful resources, and specific dangers. On the plus side, if we pick our landing site sensibly, we don’t need to take water. Water is heavy, and there’s nothing we can do to make it lighter. It takes up space, and there’s nothing we can do to make it smaller. And, even with the very best recycling facilities, the astronauts will still require a certain amount of spare water. Yet on Mars, there are many places where water, in the form of ice, is just part of the soil. Stick a shovel in the ground, and half of what gets picked up is water ice. And we can use that water for all sorts of things, not just drinking. We can use it for chemistry.

We can split it using electrolysis into its component gases. We can breathe the oxygen – which saves us from having to take tanked air. And if we recombine it with the hydrogen, we have an explosive mixture we might use as a rudimentary rocket fuel. If we go one stage further, we can scavenge the carbon from Mars’s carbon dioxide atmosphere and synthesise hydrocarbons for a better burn.

That carbon dioxide is also vital for plant growth. Add water, and a growing medium, and suddenly supplementing our freeze-dried packets of food becomes not just a possibility, but a mission goal. Humans consume a lot of calories, but we also eat with our eyes. A side salad isn’t just nutrition, but a morale booster.

Then there’s the stuff of Mars itself. We can use that as a construction material: make bricks from it, or simply heap it up and over our existing structures. And we really need to do that because life on the Martian surface isn’t straightforward.

The red dust has become a nanoparticle and is a major hazard, both to us and to our machines

Most immediately, there’s the temperature. Mars is an average of 80 million kilometres (50 million miles) further from the Sun, and its atmosphere is too thin to buffer the extremes of daily variations. Daytime temperatures in high summer can reach a balmy 21ºC (70ºF), but that same day, just before dawn, will have recorded -90ºC (-130ºF). Temperatures can fall as far as to freeze carbon dioxide out of the atmosphere. The extra insulation provided by several feet of Martian soil is going to be a welcome bonus.

Moreover, it’ll help with a long-term threat: radiation. The Sun spits out charged particles all the time, as well as high-energy light in the form of gamma and X-rays. On Earth, and to a lesser extent, on the Moon, we’re protected by Earth’s large magnetic field, which extends out into space and deflects the solar wind around us. Mars has no such magnetic field, and while conditions at the surface aren’t acutely life-threatening, every day that astronauts spend on the surface of Mars, they are accumulating radiation damage 10 to 20 times faster than they would on Earth – not counting the occasional solar flare that squeezes a decade’s worth of exposure into a single event.

Burying the astronauts’ base beneath the ground is one relatively easy solution to this radiation problem. So is building it inside a cave – volcanic areas of Mars are the sites of lava tubes that now form huge tunnels, with access through partial roof collapses.

The soil itself is toxic, rich with perchlorates. While these are a potential source of oxygen, perchlorates are water-soluble: contaminated soil cannot be used as a growing medium.

Then there is the dust. The red dust has been formed by hundreds of millions of years of continuous grinding of volcanic ash, becoming so fine that even the weak Martian winds can carry and keep it aloft for weeks at a time. The dust has become a nanoparticle – averaging 3μm (one 10,000th of an inch) – and is a major hazard, both to us and to our machines. It would be all but impossible to exclude the dust from living spaces: astronauts would carry it in from trips outside, even with assiduous measures – washing, hoovering, anti-static screens and air filtration – it would become part of the air they breathed and the food they ate. As well as the perchlorates previously mentioned, there’s other cancer-causing compounds, and the damage that fine-grained rock powder can cause specifically to lungs and eyes.

We’ve already lost one rover to the dust, which coated its solar panels. The more complex the machinery we take, the more certain we have to be of our seals and surfaces. Maintenance, together with the spare parts to back up that regime, would have to be strictly observed.

S o how might we do this? We have parameters set by the number of crew we send, how long they plan to initially stay for, and what they intend to do when they get there. We have to plan to shelter, water and feed them, and then bring them home – and, if we’re intending anything other than a one-time visit, we need to keep our eye on the long game: what kind of infrastructure can we build that will be useful into the future?

Breaking down the problem into manageable bites is by far the most feasible way. What we learn from such incremental efforts – and what we have already learned – can be used to guide us as we work our way through the various elements that we need to execute a successful, and sustainable, Mars mission.

We must prioritise a safe landing without encumbering the descent with the weight of food, fuel, air and water

The first stage would be to increase our capabilities in low Earth orbit. A multi-month journey to Mars will require the largest spaceship we’ve ever built, and almost certainly something that can’t be lofted in a single launch. It’ll need to be constructed in space, using methods similar to the International Space Station. Fuel, together with everything needed to maintain life for the long journey, will need to be shipped from Earth – twice over, as it’ll be coming back. The descent craft will be a separate part of the ship, while the main portion stays in Mars orbit.

The second stage would be to send supplies ahead to the designated landing area. If we can, we should send robotic, self-erecting modules. This would ensure that there would be somewhere safe for the newly arrived astronauts to go, and enable us to prioritise a safe landing without encumbering the descent phase with the additional weight of food, fuel, air and water. And, this way, we wouldn’t have to commit astronauts to the long and arduous journey to Mars until we know there’s enough equipment in place to sustain them. If one rocket went astray – more than one is statistically likely to be lost – we’d simply send another.

One of the pieces of kit we’d send ahead would be an ascent module, an empty ship capable not just of landing on Mars, but also refuelling itself from the Martian atmosphere, ready for a return to the transfer ship in orbit.

T o be clear, none of this is risk-free. Famously, an alternative speech was delivered in 1969 to the US president Richard Nixon in advance of Apollo 11’s landing, covering the scenario for failure. While our careful preparation has made success more likely, there are still situations that would be all but impossible to recover from. The main cause of this is how long it would take us to react to the unforeseen.

Supply chains are one of the most underestimated and misunderstood factors underpinning a modern economy. We are very used to being able to order anything, from anywhere, and it being available in a matter of days, if not hours. Manufacturers run just-in-time stocks from their suppliers, and retailers promise almost immediate delivery. Behind those storefronts lies a fantastically complex web of communications, transport, inventory control and personnel. We notice it only when it fails.

Almost everywhere on Earth is connected. Vital medicines, microchips, engine parts, even live organs for donation, are moved seamlessly between countries and continents. But there are places where this isn’t true, and they give us a first insight as to what challenges any Martian colonist might face.

Antarctica, despite our technology, remains one of the most isolated and inhospitable places on the planet. Almost everything that is needed – barring air, and water – has to be shipped or flown in, over vast distances and not without risk. Heavy seas, thick ice, a storm, an extra-cold snap: all see food and fuel stuck on a dock or on a runway. Antarctic bases don’t run a just-in-time supply chain, because when that supply chain is inevitably interrupted, people might die. Planning for those interruptions means having to take, and store, far more than is normally needed. Those of us who aren’t preppers will baulk at the amount of groceries required to keep a single person fed for a couple of months: the wintertime population of the Amundsen-Scott base, right on the South Pole, is 50.

Food, of course, can always be rationed. Heating can be reduced to one or two heavily insulated modules. There are back-up generators, and a doctor on site, and a modern, satellite-connected communications suite. Scientists are supported by a whole team of electricians, plumbers and technicians, working around the clock to maintain the infrastructure of the base, catching problems before they become critical and providing workaround solutions through their expertise.

The risk of death – by starvation, cold, asphyxiation, accident, illness, disease – has to be accepted

None of which has stopped problems occurring. Notably, if the base doctor falls ill and requires surgery, as has happened twice, the doctor ends up operating on themselves. In both cases, medical evacuation was impossible due to poor weather conditions and the distances involved. Some permanent bases still insist that personnel have their appendix removed before arrival.

Now, imagine that happening on Mars. A fully functioning base, sited in the most favourable position, and enjoying a multiply redundant infrastructure maintained by shifts of highly motivated and trained engineers, is still in a far, far more precarious position than any Antarctic base is today. A mercy dash to air-drop urgent medical supplies in Antarctica from the South Island of New Zealand is difficult but possible: the travel time, once everything is in place, is a matter of hours. Meanwhile, if the launch window is being kind, Earth to Mars is nine months. New generations of space drives will inevitably reduce that, but nothing can be done to erase the vast distances between the two planets. At best, 56 million kilometres ( c 35 million miles). At worst, when Earth is one side of the Sun, and Mars the other, 400 million kilometres ( c 250 million miles).

Without a doubt, it would be the longest supply chain in history, at the end of which is the harshest environment we have ever encountered. Even in the Age of Sail, the journey from England to Australia was faster.

If you’re the doctor on the first Mars mission, you have to decide not what drugs and bandages and surgical equipment you’re taking, but what you’re not taking. What can you do without? Both space and weight are limited. If you’re the engineer: how are you going to choose between this critical spare part and that critical spare part? Of course, you could ask the mission planners to send one – or two – of everything. But, given all that’s gone before, how feasible is that? At some point, enough will be too much. The risk of death – by starvation, by cold, by asphyxiation, by accident, by illness, by disease – has to be accepted.

As with all pioneers, the heaviest burden will fall on those who go first. They will be the most uncomfortable, the most precarious, the most vulnerable. Those who follow afterwards will have it, if not easy, certainly easier. The infrastructure of the initial base is designed to be expanded, as long as Earth holds faith with the project. For it’s certain that Mars will be utterly dependent on Earth for decades. How, though, would a Mars colony grow towards independence? Can we see that far ahead?

Manufacturing is a key technology here: not just the usual but vital supply of spare parts, but also the chemicals required for life. Specially tailored medicines, dietary supplements and plant nutrients will provide a measure of security for colonists; 3D printers with a vast library of models can start to deal with the physical, while the biological components can be conjured by automated synthesis machines.

Another cornerstone of a more independent Mars would be the colonists themselves – and specifically their education. Necessity is often the mother of invention, but Mars would be a very harsh taskmaster. A Martian colonist would need to devote a significant portion of their time to learning. The level of technology required to sustain a working colony would be high, and the number of personnel limited by available food and air. With everyone an expert in two or three separate areas of knowledge, a tragic accident to one need not turn into a crisis for all.

The highly precarious nature of life on Mars will inevitably lead to new social mores and codes of behaviour. Far from being rugged individualists, Martians will rely on each other for their very lives in a highly interdependent way – and they’ll reflect that, both in their relationships and their laws.

Just how divergent colonists become from the mother planet remains to be seen. But an independent Mars wouldn’t be a carbon-copy of any Earth society. It would be startlingly, and profoundly, alien.

The Red Planet: A Natural History of Mars (2022) by Simon Morden is published by Pegasus Books.

Return of the descendants

I migrated to my ancestral homeland in a search for identity. It proved to be a humbling experience in (un)belonging

Jessica Buchleitner

Neuroscience

How to make a map of smell

We can split light by a prism, sounds by tones, but surely the world of odour is too complex and personal? Strangely, no

Jason Castro

The cell is not a factory

Scientific narratives project social hierarchies onto nature. That’s why we need better metaphors to describe cellular life

Charudatta Navare

Anthropology

Societies of perpetual movement

Why do hunter-gatherers refuse to be sedentary? New answers are emerging from the depths of the Congolese rainforest

Cecilia Padilla-Iglesias

Rethinking the homunculus

When we discovered that the brain contained a map of the body it revolutionised neuroscience. But it’s time for an update

Moheb Costandi

Science must become attuned to the subtle conversations that pervade all life, from the primordial to the present

David Waltner-Toews

• Ask An Astrobiologist
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Life on Mars: A Definite Possibility

Was Mars once a living world? Does life continue, even today, in a holding pattern, waiting until the next global warming event comes along? Many people would like to believe so. Scientists are no exception. But so far no evidence has been found that convinces even a sizable minority of the scientific community that the red planet was ever home to life. What the evidence does indicate, though, is that Mars was once a habitable world . Life, as we know it, could have taken hold there.

The discoveries made by NASA ’s Opportunity rover at Eagle Crater earlier this year (and being extended now at Endurance Crater) leave no doubt that the area was once ‘drenched’ in water . It might have been shallow water. It might not have stuck around for long. And billions of years might have passed since it dried up. But liquid water was there, at the martian surface, and that means that living organisms might have been there, too.

So suppose that Eagle Crater – or rather, whatever land formation existed in its location when water was still around – was once alive. What type of organism might have been happy living there?

Probably something like bacteria. Even if life did gain a foothold on Mars, it’s unlikely that it ever evolved beyond the martian equivalent of terrestrial single-celled bacteria. No dinosaurs; no redwoods; no mosquitoes – not even sponges, or tiny worms. But that’s not much of a limitation, really. It took life on Earth billions of years to evolve beyond single-celled organisms. And bacteria are a hardy lot. They are amazingly diverse, various species occupying extreme niches of temperature from sub-freezing to above-boiling; floating about in sulfuric acid; getting along fine with or without oxygen. In fact, there are few habitats on Earth where one or another species of bacterium can’t survive.

What kind of microbe, then, would have been well adapted to the conditions that existed when Eagle Crater was soggy? Benton Clark III , a Mars Exploration Rover ( MER ) science team member, says his “general favorite” candidates are the sulfate-reducing bacteria of the genus Desulfovibrio . Microbiologists have identified more than 40 distinct species of this bacterium.

Eating Rocks

We tend to think of photosynthesis as the engine of life on Earth. After all, we see green plants nearly everywhere we look and virtually the entire animal kingdom is dependent on photosynthetic organisms as a source of food. Not only plants, but many microbes as well, are capable of carrying out photosynthesis. They’re photoautotrophs: they make their own food by capturing energy directly from sunlight.

But Desulfovibrio is not a photoautotroph; it’s a chemoautotroph. Chemoautotrophs also make their own food, but they don’t use photosynthesis to do it. In fact, photosynthesis came relatively late in the game of life on Earth. Early life had to get its energy from chemical interactions between rocks and dirt, water, and gases in the atmosphere. If life ever emerged on Mars, it might never have evolved beyond this primitive stage.

Desulfovibrio makes its home in a variety of habitats. Many species live in soggy soils, such as marshes and swamps. One species was discovered all snug and cozy in the intestines of a termite. All of these habitats have two things in common: there’s no oxygen present; and there’s plenty of sulfate available.

Sulfate reducers, like all chemoautotrophs, get their energy by inducing chemical reactions that transfer electrons between one molecule and another. In the case of Desulfovibrio, hydrogen donates electrons, which are accepted by sulfate compounds. Desulfovibrio, says Clark, uses “the energy that it gets by combining the hydrogen with the sulfate to make the organic compounds” it needs to grow and to reproduce.

The bedrock outcrop in Eagle Crater is chock full of sulfate salts. But finding a suitable electron donor for all that sulfate is a bit more troublesome. “My calculations indicate [that the amount of hydrogen available is] probably too low to utilize it under present conditions,” says Clark. “But if you had a little bit wetter Mars, then there [would] be more water in the atmosphere, and the hydrogen gas comes from the water” being broken down by sunlight.

So water was present; sulfate and hydrogen could have as an energy source. But to survive, life as we know it needs one more ingredient carbon. Many living things obtain their carbon by breaking down the decayed remains of other dead organisms. But some, including several species of Desulfovibrio, are capable of creating organic material from scratch, as it were, drawing this critical ingredient of life directly from carbon dioxide (CO 2 ) gas. There’s plenty of that available on Mars.

All this gives reason to hope that life that found a way to exist on Mars back in the day when water was present. No one knows how long ago that was. Or whether such a time will come again. It may be that Mars dried up billions of years ago and has remained dry ever since. If that is the case, life is unlikely to have found a way to survive until the present.

Tilting toward Life

But Mars goes through cycles of obliquity, or changes in its orbital tilt. Currently, Mars is wobbling back and forth between 15 and 35 degrees’ obliquity, on a timescale of about 100,000 years. But every million years or so, it leans over as much as 60 degrees. Along with these changes in obliquity come changes in climate and atmosphere. Some scientists speculate that during the extremes of these obliquity cycles, Mars may develop an atmosphere as thick as Earth’s, and could warm up considerably. Enough for dormant life to reawaken.

“Because the climate can change on long terms,” says Clark, ice in some regions on Mars periodically could “become liquid enough that you would be able to actually come to life and do some things – grow, multiply, and so forth – and then go back to sleep again” when the thaw cycle ended. There are organisms on Earth that, when conditions become unfavorable, can form “spores which are so resistant that they can last for a very long time. Some people think millions of years, but that’s a little controversial.”

Desulfovibrio is not such an organism. It doesn’t form spores. But its bacterial cousin, Desulfotomaculum, does. “Usually the spores form because there’s something missing, like, for example, if hydrogen’s not available, or if there’s too much [oxygen], or if there’s not sulfate. The bacteria senses that the food source is going away, and it says, ‘I’ve got to hibernate,’ and will form the spores. The spores will stay dormant for extremely long periods of time. But they still have enough machinery operative that they can actually sense that nutrients are available. And then they’ll reconvert again in just a matter of hours, if necessary, to a living, breathing bacterium, so to speak. It’s pretty amazing,” says Clark.

That is not to say that future Mars landers should arrive with life-detection equipment tuned to zero in on species of Desulfovibrio or Desulfotomaculum. There is no reason to believe that life on Mars, if it ever emerged, evolved along the same lines as life on Earth, let alone that identical species appeared on the two planets. Still, the capabilities of various organisms on Earth indicate that life on Mars – including dormant organisms that could spring to life again in another few hundred thousand years – is certainly possible.

Clark says that he doesn’t “know that there’s any organism on Earth that could really operate on Mars, but over a long period of time, as the martian environment kept changing, what you would expect is that whatever life had started out there would keep adapting to the environment as it changed.”

Detecting such organisms is another matter. Don’t look for it to happen any time soon. Spirit and Opportunity were not designed to search for signs of life, but rather to search for signs of habitability. They could be rolling over fields littered with microscopic organisms in deep sleep and they’d never know it. Even future rovers will have a tough time identifying the martian equivalent of dormant bacterial spores.

“The spores themselves are so inert,” Clark says, “it’s a question, if you find a spore, and you’re trying to detect life, how do you know it’s a spore, [and not] just a little particle of sand? And the answer is: You don’t. Unless you can find a way to make the spore do what’s called germinating, going back to the normal bacterial form.” That, however, is a challenge for another day.

Planet Mars, explained

The rusty world is full of mysteries—and some of the solar system's most extreme geology. Learn more about Earth's smaller, colder neighbor.

The red planet Mars, named for the Roman god of war, has long been an omen in the night sky. And in its own way, the planet’s rusty red surface tells a story of destruction. Billions of years ago, the fourth planet from the sun could have been mistaken for Earth’s smaller twin, with liquid water on its surface—and maybe even life.

Now, the world is a cold, barren desert with few signs of liquid water. But after decades of study using orbiters, landers, and rovers, scientists have revealed Mars as a dynamic, windblown landscape that could—just maybe—harbor microbial life beneath its rusty surface even today.

Longer year and shifting seasons

With a radius of 2,106 miles, Mars is the seventh largest planet in our solar system and about half the diameter of Earth. Its surface gravity is 37.5 percent of Earth’s.

Mars rotates on its axis every 24.6 Earth hours, defining the length of a Martian day, which is called a sol (short for “solar day”). Mars’s axis of rotation is tilted 25.2 degrees relative to the plane of the planet’s orbit around the sun, which helps give Mars seasons similar to those on Earth. Whichever hemisphere is tilted closer to the sun experiences spring and summer, while the hemisphere tilted away gets fall and winter. At two specific moments each year—called the equinoxes—both hemispheres receive equal illumination.

But for several reasons, seasons on Mars are different from those on Earth. For one, Mars is on average about 50 percent farther from the sun than Earth is, with an average orbital distance of 142 million miles. This means that it takes Mars longer to complete a single orbit, stretching out its year and the lengths of its seasons. On Mars, a year lasts 669.6 sols, or 687 Earth days, and an individual season can last up to 194 sols, or just over 199 Earth days.

The angle of Mars’s axis of rotation also changes much more often than Earth's, which has led to swings in the Martian climate on timescales of thousands to millions of years. In addition, Mars’s orbit is less circular than Earth’s, which means that its orbital velocity varies more over the course of a Martian year. This annual variation affects the timing of the red planet’s solstices and equinoxes. On Mars, the northern hemisphere’s spring and summer are longer than the fall and winter.

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There’s another complicating factor: Mars has a far thinner atmosphere than Earth, which dramatically lessens how much heat the planet can trap near its surface. Surface temperatures on Mars can reach as high as 70 degrees Fahrenheit and as low as -225 degrees Fahrenheit, but on average, its surface is -81 degrees Fahrenheit, a full 138 degrees colder than Earth’s average temperature.

Windy and watery, once

The primary driver of modern Martian geology is its atmosphere, which is mostly made of carbon dioxide, nitrogen, and argon. By Earth standards, the air is preposterously thin; air pressure atop Mount Everest is about 50 times higher than it is at the Martian surface . Despite the thin air, Martian breezes can gust up to 60 miles an hour, kicking up dust that fuels huge dust storms and massive fields of alien sand dunes.

Once upon a time, though, wind and water flowed across the red planet. Robotic rovers have found clear evidence that billions of years ago, lakes and rivers of liquid water coursed across the red planet’s surface. This means that at some point in the distant past, Mars’s atmosphere was sufficiently dense and retained enough heat for water to remain liquid on the red planet’s surface. Not so today: Though water ice abounds under the Martian surface and in its polar ice caps, there are no large bodies of liquid water on the surface there today.

Mars also lacks an active plate tectonic system, the geologic engine that drives our active Earth, and is also missing a planetary magnetic field. The absence of this protective barrier makes it easier for the sun’s high-energy particles to strip away the red planet’s atmosphere, which may help explain why Mars’s atmosphere is now so thin. But in the ancient past—up until about 4.12 to 4.14 billion years ago —Mars seems to have had an inner dynamo powering a planet-wide magnetic field. What shut down the Martian dynamo? Scientists are still trying to figure out.

High highs and low lows

Like Earth and Venus, Mars has mountains, valleys, and volcanoes, but the red planet’s are by far the biggest and most dramatic. Olympus Mons, the solar system’s largest volcano, towers some 16 miles above the Martian surface, making it three times taller than Everest. But the base of Olympus Mons is so wide—some 374 miles across—that the volcano’s average slope is only slightly steeper than a wheelchair ramp. The peak is so massive, it curves with the surface of Mars. If you stood at the outer edge of Olympus Mons, its summit would lie beyond the horizon.

Mars has not only the highest highs, but also some of the solar system’s lowest lows. Southeast of Olympus Mons lies Valles Marineris, the red planet’s iconic canyon system. The gorges span about 2,500 miles and cut up to 4.3 miles into the red planet’s surface. The network of chasms is four times deeper—and five times longer—than Earth’s Grand Canyon, and at its widest, it’s a staggering 200 miles across. The valleys get their name from Mariner 9, which became the first spacecraft to orbit another planet when it arrived at Mars in 1971.

A tale of two hemispheres

About 4.5 billion years ago, Mars coalesced from the gaseous, dusty disk that surrounded our young sun. Over time, the red planet’s innards differentiated into a core, a mantle, and an outer crust that’s an average of 40 miles thick.

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Its core is likely made of iron and nickel, like Earth’s, but probably contains more sulfur than ours. The best available estimates suggest that the core is about 2,120 miles across, give or take 370 miles—but we don’t know the specifics. NASA’s InSight lander aims to unravel the mysteries of Mars’s interior by tracking how seismic waves move through the red planet.

Mars’s northern and southern hemispheres are wildly different from one another, to a degree unlike any other planet in the solar system. The planet’s northern hemisphere consists mostly of low-lying plains, and the crust there can be just 19 miles thick. The highlands of the southern hemisphere, however, are studded with many extinct volcanoes, and the crust there can get up to 62 miles thick.

What happened? It’s possible that patterns of internal magma flow caused the difference, but some scientists think it's the result of Mars suffering one or several major impacts. One recent model suggests Mars got its two faces because an object the size of Earth’s moon slammed into Mars near its south pole.

Both hemispheres do have one thing in common: They’re covered in the planet’s trademark dust, which gets its many shades of orange, red, and brown from iron rust.

Cosmic companions

At some point in the distant past, the red planet gained its two small and irregularly shaped moons, Phobos and Deimos. The two lumpy worlds, discovered in 1877, are named for the sons and chariot drivers of the god Mars in Roman mythology. How the moons formed remains unsolved. One possibility is that they formed in the asteroid belt and were captured by Mars’s gravity. But recent models instead suggest that they could have formed from the debris flung up from Mars after a huge impact long ago.

Deimos, the smaller of the two moons, orbits Mars every 30 hours and is less than 10 miles across. Its larger sibling Phobos bears many scars, including craters and deep grooves running across its surface. Scientists have long debated what caused the grooves on Phobos. Are they tracks left behind by boulders rolling across the surface after an ancient impact, or signs that Mars’s gravity is pulling the moon apart?

Either way, the moon’s future will be considerably less groovy. Each century, Phobos gets about six feet closer to Mars; in 50 million years or so, the moon is projected either to crash into the red planet’s surface or break into smithereens.

Missions to Mars

Since the 1960s, humans have robotically explored Mars more than any other planet beyond Earth. Currently, eight missions from the U.S., European Union, Russia, and India are actively orbiting Mars or roving across its surface. But getting safely to the red planet is no small feat. Of the 45 Mars missions launched since 1960 , 26 have had some component fail to leave Earth, fall silent en route, miss orbit around Mars, burn up in the atmosphere, crash on the surface, or die prematurely.

More missions are on the horizon, including some designed to help search for Martian life. NASA is building its Mars 2020 rover to cache promising samples of Martian rock that a future mission would return to Earth. In 2020, the European Space Agency and Roscosmos plan to launch a rover named for chemist Rosalind Franklin , whose work was crucial to deciphering the structure of DNA. The rover will drill into Martian soil to hunt for signs of past and present life. Other countries are joining the fray, making space exploration more global in the process. In July 2020, the United Arab Emirates is slated to launch its Hope orbiter , which will study the Martian atmosphere.

Perhaps humans will one day join robots on the red planet. NASA has stated its goal to send humans back to the moon as a stepping-stone to Mars. Elon Musk, founder and CEO of SpaceX, is building a massive vehicle called Starship in part to send humans to Mars. Will humans eventually build a scientific base on the Martian surface, like those that dot Antarctica? How will human activity affect the red planet or our searches for life there?

Time will tell. But no matter what, Mars will continue to occupy the human imagination, a glimmering red beacon in our skies and stories.

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Curiosity Rover Science

Landing at Gale Crater, Mars Science Laboratory is assessing whether Mars ever had an environment capable of supporting microbial life. Determining past habitability on Mars gives NASA and the scientific community a better understanding of whether life could have existed on the Red Planet and, if it could have existed, an idea of where to look for it in the future.

Science Objectives

To contribute to the four Mars exploration science goals and meet its specific goal of determining Mars' habitability, Curiosity has the following science objectives:

Biological objectives

Geological and geochemical objectives, planetary process objectives, surface radiation objective.

1. Determine the nature and inventory of organic carbon compounds 2. Inventory the chemical building blocks of life (carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur) 3. Identify features that may represent the effects of biological processes

1. Investigate the chemical, isotopic, and mineralogical composition of the Martian surface and near-surface geological materials 2. Interpret the processes that have formed and modified rocks and soils

1. Assess long-timescale (i.e., 4-billion-year) atmospheric evolution processes 2. Determine present state, distribution, and cycling of water and carbon dioxide

Characterize the broad spectrum of surface radiation, including galactic cosmic radiation, solar proton events, and secondary neutrons

Science Highlights

With over a decade of exploration, Curiosity has unveiled the keys to some of science's most unanswered questions about Mars. Did Mars ever have the right environmental conditions to support small life forms called microbes? Early in its mission, Curiosity's scientific tools found chemical and mineral evidence of past habitable environments on Mars. It continues to explore the rock record from a time when Mars could have been home to microbial life.

Science Instruments

From cameras to environmental and atmospheric sensors, the Curiosity rover has a suite of state-of-the-art science instruments to achieve its goals.

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James Webb Space Telescope

Perseverance Rover

Parker Solar Probe

Essay on Life on Mars for Students and Children

500 words essay on life on mars.

Mars is the fourth planet from the sun in our solar system. Also, it is the second smallest planet in our solar system. The possibility of life on mars has aroused the interest of scientists for many years. A major reason for this interest is due to the similarity and proximity of the planet to Earth. Mars certainly gives some indications of the possibility of life.

Possibilities of Life on Mars

In the past, Mars used to look quite similar to Earth. Billions of years ago, there were certainly similarities between Mars and Earth. Furthermore, scientists believe that Mars once had a huge ocean. This ocean, experts believe, covered more of the planet’s surface than Earth’s own oceans do so currently.

Moreover, Mars was much warmer in the past that it is currently. Most noteworthy, warm temperature and water are two major requirements for life to exist. So, there is a high probability that previously there was life on Mars.

Life on Earth can exist in the harshest of circumstances. Furthermore, life exists in the most extreme places on Earth. Moreover, life on Earth is available in the extremely hot and dry deserts. Also, life exists in the extremely cold Antarctica continent. Most noteworthy, this resilience of life gives plenty of hope about life on Mars.

There are some ingredients for life that already exist on Mars. Bio signatures refer to current and past life markers. Furthermore, scientists are scouring the surface for them. Moreover, there has been an emergence of a few promising leads. One notable example is the presence of methane in Mars’s atmosphere. Most noteworthy, scientists have no idea where the methane is coming from. Therefore, a possibility arises that methane presence is due to microbes existing deep below the planet’s surface.

One important point to note is that no scratching of Mars’s surface has taken place. Furthermore, a couple of inches of scratching has taken place until now. Scientists have undertaken analysis of small pinches of soil. There may also have been a failure to detect signs of life due to the use of faulty techniques. Most noteworthy, there may be “refugee life” deep below the planet’s surface.

Get the huge list of more than 500 Essay Topics and Ideas

Challenges to Life on Mars

First of all, almost all plants and animals cannot survive the conditions on the surface of Mars. This is due to the extremely harsh conditions on the surface of Mars.

Another major problem is the gravity of Mars. Most noteworthy, the gravity on Mars is 38% to that of Earth. Furthermore, low gravity can cause health problems like muscle loss and bone demineralization.

The climate of Mars poses another significant problem. The temperature at Mars is much colder than Earth. Most noteworthy, the mean surface temperatures of Mars range between −87 and −5 °C. Also, the coldest temperature on Earth has been −89.2 °C in Antarctica.

Mars suffers from a great scarcity of water. Most noteworthy, water discovered on Mars is less than that on Earth’s driest desert.

Other problems include the high penetration of harmful solar radiation due to the lack of ozone layer. Furthermore, global dust storms are common throughout Mars. Also, the soil of Mars is toxic due to the high concentration of chlorine.

To sum it up, life on Mars is a topic that has generated a lot of curiosity among scientists and experts. Furthermore, establishing life on Mars involves a lot of challenges. However, the hope and ambition for this purpose are well alive and present. Most noteworthy, humanity must make serious efforts for establishing life on Mars.

FAQs on Life on Mars

Q1 State any one possibility of life on Mars?

A1 One possibility of life on Mars is the resilience of life. Most noteworthy, life exists in the most extreme places on Earth.

Q2 State anyone challenge to life on Mars?

A2 One challenge to life on Mars is a great scarcity of water.

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The Similarities Between Mars And Mars

Mars, the red planet, and fourth planet from the sun. What is Mars really like, is it cold or hot, wet or dry? Can humans live on Mars, and if so how? For decades scientists have been studying Mars, they have been using rovers and from there they collected data, samples, and took pictures. These rovers study Mars’ atmosphere, temperatures, weather, if it has water, and a lot more. With all of the data the scientists have gathered we know that Mars’ atmosphere is a lot different than our, yet

Life On Mars: The Colonization Of Mars

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In the article “Mars Shows Signs of Having Flowing Water, Possible Niches for Life, NASA Says” written by Kenneth Chang the central idea is that there is a probability of life on another planet other than Earth. The reason this article is important to us is because with these findings, researchers will be eager to follow up on the discovery so that we can find out if the probable signs of liquid water flowing mean that life could sustain on Mars. For many years scientists have been interested in

Is There Life on Mars?

THERE LIFE ON MARS? If you have a chance to go to a country side where you may have a clear view of the sky at night, you probably will discover a red star. That is probably Mars. With its bright and reddish color, Mars stands out for and easily noticed since the ancient times (Discovery). In 1877, astronomer Giovanni Schiaparelli discovered several crisscrossing lines on Mars that he believed to be the canals of water (Discovery). Go along with the hypothesis that life existed on Mars, several processes

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Essay on Mars

Students are often asked to write an essay on Mars in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Mars

Mars: an introduction.

Mars, also known as the Red Planet, is the fourth planet from the sun in our solar system. It gets its nickname from its reddish appearance, caused by iron oxide (rust) on its surface.

Physical Features

Mars has the tallest volcano and the deepest canyon in the solar system. Olympus Mons is the volcano, and Valles Marineris is the canyon. Mars also has polar ice caps made of water and carbon dioxide.

Life on Mars

Scientists have not found life on Mars yet. However, they believe that the planet may have had conditions suitable for life in the past. Now, Mars is too cold and dry for life.

Mars Exploration

Several spacecrafts have been sent to Mars. These missions help scientists learn about the planet’s climate and geology, and search for signs of life. The Mars rovers, like Perseverance, are particularly important in this exploration.

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250 Words Essay on Mars

Introduction.

Mars, the fourth planet from the sun in our solar system, has been a subject of fascination for scientists and space enthusiasts for centuries. This celestial body, often referred to as the ‘Red Planet’, has been explored by numerous space missions, providing us with valuable insights.

Geographical Features

Mars exhibits a variety of geographical features that are similar to Earth’s. It hosts the largest volcano in the solar system, Olympus Mons, and a grand canyon, Valles Marineris, which is nearly five times the depth of Earth’s Grand Canyon. The planet’s reddish appearance is due to iron oxide, or rust, on its surface.

Atmospheric Conditions

Mars’ thin atmosphere, composed primarily of carbon dioxide, provides inadequate protection from solar radiation. This makes the planet’s surface inhospitable to known life forms. The average temperature on Mars is a chilly -80 degrees Fahrenheit, with polar ice caps composed of water and carbon dioxide.

Search for Life

The search for life on Mars has been a primary goal of numerous missions. While no definitive evidence of past or present life has been found, scientists have discovered signs of liquid water and organic molecules, which are the building blocks of life.

Future Exploration

Future missions to Mars aim to answer questions about its geology, climate, and potential for life. The recent Perseverance rover mission by NASA and the planned human missions signify our continuous quest to unravel the mysteries of this intriguing planet.

In conclusion, Mars, with its similarities and differences to Earth, continues to captivate our curiosity, pushing the boundaries of our knowledge and technological capabilities in space exploration.

500 Words Essay on Mars

The red planet: an overview.

Mars, often referred to as the Red Planet due to its reddish appearance, is the fourth planet from the Sun in our solar system. Its distinct color is attributed to iron oxide, or rust, on its surface. It is a terrestrial planet with a thin atmosphere, possessing surface features both reminiscent of both Earth and the moon.

Geographical Features and Atmosphere

Mars has the highest mountain and the deepest, longest canyon in the solar system. Olympus Mons, the highest mountain, is nearly three times the height of Mount Everest, which is about 5.5 miles high. Valles Marineris, the longest canyon, would stretch from New York City to Los Angeles on Earth. Mars’ atmosphere is composed primarily of carbon dioxide (about 96%), with minor amounts of other gases such as argon and nitrogen. The climate on Mars is much colder than on Earth, with an average temperature around -80 degrees Fahrenheit.

Exploration of Mars

The exploration of Mars has been an important part of the space exploration programs of several countries. The first successful flyby of Mars was by Mariner 4 in 1965. Since then, numerous spacecraft have been sent to explore Mars, including the Viking missions in the 1970s and, more recently, the Mars Rover missions. The primary focus of these missions is to search for evidence of past or present life on Mars.

Potential for Life

The question of life on Mars centers around the planet’s past and present habitability, or its potential to host life. While no direct evidence of past or present biological activity has been found, several pieces of evidence suggest that Mars could have supported life in the past. For instance, the discovery of ancient riverbeds and polar ice caps implies that liquid water, an essential ingredient for life as we know it, once existed on the planet’s surface.

Human Settlement

The prospect of human settlement on Mars has been a tantalizing challenge for scientists and engineers. The technical and logistical hurdles are significant, including the need for life support systems, sustainable food production, and protection from solar and cosmic radiation. Despite these challenges, organizations like NASA and SpaceX are actively working towards making human Mars missions a reality in the foreseeable future.

Mars, with its similarities to Earth and its potential for harboring life, continues to captivate our curiosity. The ongoing exploration of this fascinating planet not only expands our understanding of the universe but also propels us towards becoming a multi-planetary species. As we continue to explore Mars, we may not only answer the age-old question of whether we are alone in the universe but also set the stage for our future as space explorers.

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