Where there’s water, there’s life — but Mars may not be as watery as we thought. We already knew that liquid water can’t really last on the surface: it would evaporate in no time. We also knew that water ice is plentiful in some areas on Mars. But what about liquid water?
Based on observations in 2018, astronomers started to suspect that Mars may have underground lakes beneath some masses of ice. This was based on observations from a radar instrument aboard the ESA (European Space Agency) Mars Express orbiter.
The idea isn’t as crazy as it sounds. Earth also has a lot of underground water, and even frozen moons like Europa or Ganymede are thought to have large masses of subsurface water. Mars having a subsurface lake below its ice cap wouldn’t be all that weird — especially as the data seemed to back it up.
But the data may not back it up after all.
Radar instruments send out pulses of electromagnetic waves; the wave passes through different materials (in this case, the layers of Mars), and based on the electromagnetic properties of the material, a receiver captures the reflected waveform.
The initial analysis of this radar data showed some strong reflections, which researchers interpreted as bodies of water. But in a new study, Isaac Smith of Toronto’s York University now has a different idea.
Smith didn’t go to Mars or anything like that — he worked in a lab, freezing clays with liquid nitrogen, until they reached temperatures like those on Mars.
“The lab was cold,” Smith said. “It was winter in Canada at the time, and pumping liquid nitrogen into the room made it colder. I was bundled up in a hat, jacket, gloves, scarf, and a mask because of COVID-19. It was pretty uncomfortable.”
The clays in this case are called “smectites” — a type of rock formed by liquid water long time ago. He then subjected them to radar instruments similar to those used on Mars, to see their response. It was exactly like what the Mars Orbiter observed.
In a recent paper published in Geophysical Research Letters, researchers found that many of the “water” signals came from areas close to the surface, where it should be too cold for water to remain liquid, even when mixed with minerals commonly found on Mars (that can lower freezing temperature of water).
So we know that it’s probably too cold for liquid water to exist in those areas, and we have another likely candidate that could be responsible for the signal. Although it’s not yet possible to directly confirm whether what was on the radar data was liquid water, smectites, or maybe even something else, water is looking less and less likely.
But this is a win for science. Ultimately, the fact that researchers are able to derive so much information about a different planet, working with so little data, is remarkable.
“In planetary science, we often are just inching our way closer to the truth,” said Jeffrey Plaut of NASA’s Jet Propulsion Laboratory. “The original paper didn’t prove it was water, and these new papers don’t prove it isn’t. But we try to narrow down the possibilities as much as possible in order to reach consensus.”
We’ve learned a great deal about Mars in recent years. It’s not the alien-populated planet it was once believed to be, but it’s definitely not the dull, meaningless planet some portray it as. Mars is, in many ways, very much like Earth. Just like Earth, Mars hosted vast amounts of water (something we’ve also learned recently) — but unlike Earth, it no longer has a rich atmosphere, its water is only preserved in pockets, and it is (at least for the most part) lifeless.
However, it seems like the more we learn about Mars, the more questions arise. For every tantalizing answer, three more burning questions arise. Thankfully, more missions are en-route to Mars, including China’s Tianwen-1, the United Arab Emirates’ Hope Probe, and NASA’s Perseverance rover, which could help solve some of these mysteries. For now, here are some Mars facts we’ve recently learned.
Mars is a ‘wobbly’ planet just like Earth, but we’re not really sure why
As the Earth spins during its day, it also wobbles and bobbles ever so slightly around its own axis. Astronomers aren’t really sure why this is happening, but they recently learned that Mars also does it.
It’s called the Chandler Wobble: when a rotating body’s mass isn’t distributed evenly, which causes a wobble. In Earth’s case, it’s mostly caused by its shape, which isn’t perfectly round. In the case of the much rounder Mars, we’re not really sure why it happens, but it could be because of atmospheric motions.
The Martian landscape may have been shaped by megafloods
Mars is, for the most part, a barren and inhospitable place. But go back a couple billion years, and the planet would have been much different. Researchers are now pretty sure that it was once home to oceans and river systems, but according to a new study, it was also subjected to powerful megafloods.
According to the new study, the megafloods would have been triggered by an asteroid impact 4 billion years ago. Although the water is now gone long, evidence of the ripples can still be seen in the shape of the Martian sediments. “Early Mars was an extremely active planet from a geological point of view,” a co-author of the study said in a press release. “The planet had the conditions needed to support the presence of liquid water on the surface”.
Mars still has multiple bodies of liquid water
Speaking of water on Mars, September 2020 was a groundbreaking moment, as researchers published data showing that Mars still has salty lakes sealed under its icy polar regions. These subglacial lakes are exciting for two reasons: first, where there’s water there could also be life, and subglacial lakes would be an ideal place to look for life on Mars; and second, this water could also be useful in establishing a human base or settlement on Mars.
When talking about water on Mars, we usually talk in the past tense. Mars had a rich water system, but now it’s gone — the fact that it still has large bodies of liquid water came as quite a shock and made Mars much more interesting than before.
It has auroras
The Martian aurora takes place at night and is generated by the interaction of sunlight with oxygen atoms and molecules in the air. The emission is very difficult to see, even from Earth, which is relatively nearby. The Mars aurora was imaged by European Space Agency’s Trace Gas Orbiter (TGO), which explored the Martian atmospheric environment before delivering the Schiaparelli lander, which crashed on the surface due to a premature release of the parachute.
But here’s the thing: Mars gets auroras almost every day, it’s just that we can’t see them. Unlike their Earthly counterparts, however, you’d need some ultraviolet goggles to see the Martian aurora.
Mars may have had planetary rings (and may get another one)
‘Mars’ and ‘planetary rings’ don’t really seem to get together in the same sentence. After all, planetary rings seem reserved for gas giants like Jupiter or Saturn. But astronomers have recently suggested that Mars may have also had planetary rings.
Mars has two tiny moons, Phobos and Deimos. These moons rotate almost in the same plane as the Red Planet’s equator, which means the moons likely formed at the same time as Mars. However, one of the moons (Deimos) is tilted by two degrees, something which no one really bothered with until recently. Now, a team of astronomers is suggesting that this tilt can only be explained by a grandparent moon which broke down, producing planetary rings in the process.
It had a system of giant rivers that lasted billions of years
When researchers say Mars had water, it’s not a joke. Analyzing new images of the sedimentary structure of Mars, a team of researchers concluded that in order to produce what can be observed now, the Martian rivers must have lasted for a very long time — up to billions of years.
The sedimentary rocks record layers of history, and the researchers were able to determine that the channels of these ancient rivers were around 9 or 10 feet deep. Mars had “rivers that continuously shifted their gullies, creating sandbanks, similar to the Rhine or the rivers that you can find in Northern Italy,” the researchers said in their study.
It may have been habitable as early as 4.4 billion years ago
We don’t know if Mars was ever truly habitable, but there’s a good chance it was — and for a long time. A 2019 study suggests that Mars may have exhibited conditions fit for harboring life as early as 4.48 billion years ago, predating the earliest evidence of life on Earth by around 500 million years.
There’s a great deal of speculation regarding the potential for life on Mars, but if the planet ever was habitable, and if it had conditions similar to Earth, then life may have well emerged on the Red Planet before Earth. Heck, it could have even migrated from Mars to Earth on meteorites — though again, at this point, this is just speculation.
Some of its clouds are made of ground-up meteors
The first strange thing about the Martian clouds is that they exist at all. Down here on Earth, clouds form around tiny particles like grains of dust or salt which act as anchors for water vapor to condense on. But to our knowledge, this mechanism doesn’t exist on Mars.
Around two to three tons of space debris rain down on Mars, on average, every single day, and a new study suggests that these particles form the seed of Martian clouds. The findings are supported by previous research showing that a similar mechanism may help seed clouds near Earth’s poles (where the magnetic shield is weakest).
It has earthquakes — I mean ‘marsquakes’
Unlike Earth, Mars doesn’t really have an active tectonics, which means that its seismic activity is way less intense than that of Earth’s. However, after months of waiting, the Seismic Experiment for Interior Structure (SEIS) on board the InSight Mars lander detected its first ‘marsquake’.
Earthquakes (and marsquakes) are useful for researchers because they can offer information about the subsurface. By analyzing the seismic waves, researchers can infer the structure of the entire planet — that’s how we know what the Earth’s inside looks like, and that’s how we could also understand what Mars is like on the inside.
Mars also has methane
Methane is a key molecule for life. The presence of methane could enhance habitability and may even be a signature of life, but it was only confirmed independently on Mars in 2019. Using numerical modeling and geological analysis, a team of researchers at the National Institute of Astrophysics in Rome, Italy, propose not only that methane on Mars exists, but also suggest where it could be located.
Methane is a chemical compound closely associated with microbial life, but it isn’t necessarily biological in nature. There’s a very good chance that the methane is generated geologically, and this is what this new paper also suggests. However, since researchers pinpointed a promising location for future investigations into the origin of methane on Mars, we have a starting point for future missions to look into the origin of this methane.
Mars may yet hold life in salty subsurface waters
As you may have picked up already, a lot of what we’ve learned about Mars recently has to do with the water — but there’s a big reason why we focus so much on this. Water determines potential habitability, and where water exists, life (as we know it) can also exist. If water exists on Mars, this doesn’t automatically mean that life also exists, but it means that life could exist on Mars, and that’s exciting in its own right.
This is different from the study that found subglacial lakes. A 2018 study found that some of the subsurface water on Mars could be rich enough in oxygen to support aerobic life. “That’s the thing of habitability; we never thought that environment could have that much oxygen,” said one of the study authors.
Martian soil is suitable for making bricks
If you want to bake an apple pie from scratch, you may have to invent the universe first — but if you want to make bricks from Martian soil, all you need to do is press really hard on it. A team of engineers at the University of California San Diego worked with a Mars soil simulant and managed to develop durable bricks just by pressing them really hard.
All it takes is the for equivalent to a 10 pound hammer dropped from a height of one meters, they say. Surprisingly enough, with this method, you don’t need ovens or any other ingredients. The method may be compatible with additive manufacturing, meaning astronauts wanting to build a structure would simply have to lay down a layer of dirt, compact it, lay another layer and so on until they’re done.
The Martian atmosphere was stripped by solar wind
Another important question to answer is how Mars got to how it is today. How could a planet with lush river valleys, floods, and active geology become so barren? The key lies in the disappearance of its atmosphere, and according to a recent study, its atmosphere was stripped away by solar wind.
Unlike Earth, Mars lacks a global magnetic field to deflect the stream of charged particles continuously blowing off the Sun. Instead, the solar wind crashes into Mars’ upper atmosphere and can accelerate ions into space, and the atmosphere, once rich enough to support liquid water, is now all but gone.
In its early days, Mars may have been covered by ice
A large number of valley networks scar the Martian surface, but they may have been caused by water melting beneath glacial ice, not free-flowing rivers.
Funnily enough, this type of environment would have been even better for possible ancient life forms. A sheet of ice lends protection and stability, as well as shelter from solar radiation in the absence of a magnetic field (something which Mars once had, but has been gone for billions of years).
These are just some of the many things we’ve learned about Mars recently, thanks to diligent observations and several landmark Mars missions, both in orbit and on the surface of the planet. As the missions continue to unfold and expand, so too will our understanding of the Red Planet.
Undoubtedly, we missed some bits here. Is there anything you’d like to see added to this list? Mention it in the comment section.
Life-sustaining water could have existed miles beneath the surface of Mars thanks to the melting of thick ice sheets by geothermal heat, new research has found. The discovery, made by a team led by Rutgers University scientists, suggests that 4 billion years ago the most likely place for life to prosper on the Red Planet was beneath its surface.
The study, published in the latest edition of the journal Science Advances, could solve a problem that also has implications for the existence of liquid water–and thus the early development of life–on our planet too. Thus far, researchers looking into the existence of liquid water early in both Earth and Mars’histories have been puzzled by the fact that the Sun would have been up to 70% less intense in its stellar-youth.
This lack of intensity coupled with findings of liquid water at this stage in the solar system’s history is referred to as ‘the faint-sun paradox,’ and should mean that Mars conditions were cold and arid in its deep history. This conclusion was contradicted by geological evidence of liquid water on the young planet. The problem could now be solved, for Mars at least, by geothermal activity.
“Even if greenhouse gases like carbon dioxide and water vapour are pumped into the early Martian atmosphere in computer simulations, climate models still struggle to support a long-term warm and wet Mars,” explains lead author Lujendra Ojha, assistant professor in the Department of Earth and Planetary Sciences in the School of Arts and Sciences at Rutgers University, New Brunswick. “We propose that the faint young sun paradox may be reconciled, at least partly, if Mars had high geothermal heat in its past.”
The status of Mars climate billions of years ago and if freshwater could have existed its this point early in its history has been a source of heated debate in the scientific community for decades. The discussion has been further complicated by the question of whether water would have existed on the planet’s surface or deep underground? Climate models produced for Mars thus far have suggested average surface temperatures below the melting point of water at this point in its history.
Ojha and his team investigated this seeming contradiction in our understanding of Mars by modelling the average thickness of ice deposits in the Red Planet’s southern highlands. They also examined data collected by NASA’s InSight lander, which has been measuring the ‘vitals’ of the Red Planet since 2018.
Discovering that the thickness of these ice deposits did not exceed an average thickness of 2 kilometres, the team complemented this finding with estimates of both the planet’s average annual surface temperature and the flow of heat from its interior to its surface. The aim of this was to discover if the surface heat flow would have been strong enough to melt Mars’ ice sheets.
Indeed, the study seems to show that the flow of heat from both the crust and mantle of Mars would have been intense enough to begin melting at the base of its ice sheets.
Did Life on Mars prosper Beneath its Surface?
The wider implication of this revelation is that whatever the climate of Mars was like billions of years in its history if life once existed on the Red Planet, its subsurface would have been its most habitable region. Thus, life could have prospered, say the team, miles beneath the surface of our neighbour, sustained by the flow of freshwater.
Significantly, this supply of water would have existed even as Mars lost its magnetic field and its atmosphere was stripped away by harsh solar winds and blistering radiation. The process which ultimately deprived Mars of its surface liquid water. This means that life could have survived on the planet, hidden miles underground for much longer than the surface remained habitable.
“At such depths, life could have been sustained by hydrothermal activity and rock-water reactions,” says Ojha. “So, the subsurface may represent the longest-lived habitable environment on Mars.”
Our understanding of Mars has been a true rollercoaster. Centuries ago, scholars thought Mars could host rivers and oceans like on Earth and maybe teeming with life. When the first observations came in from Galileo Galilei in 1610, astronomers discovered a planet with polar ice caps that was seemingly similar to Earth, so the hypothesis seemed to stand. But as we learned increasingly more, it became apparent that Mars isn’t exactly a lush planet.
Mars is barren nowadays, and while it may have been water-rich at some point in the past, that’s not really the case now. But there’s one more twist to the story: Mars really does have ice caps, and it does have some liquid water. Granted, that water is full of salts and buried beneath the surface, but it’s still liquid water.
According to a new study, this brine can be used to produce breathable air and fuel for Martian colonists — two valuable resources we would absolutely need on the Red Planet.
The rovers we’ve sent to Mars don’t really need oxygen. They do just fine in the ultra-thin atmosphere of the planet, wandering around and doing experiments in freezing temperatures. But if we want to establish a colony (or more likely, a research base), we can’t really manage without oxygen.
In 2008, NASA’s Phoenix Mars Lander came with some good news in that regard. It “tasted” the Martian water and upon analyzing it, found out how it manages to stay liquid on the freezing temperatures of Mars.
The key is something called perchlorate, a chemical compound containing chlorine and oxygen. Perchlorate is very stable in water, and its salts are very solluble — up to the point where they absorb and collect water vapor over time. As the perchlorate absorbs more water, it also dissolves into the water, substantially lowering its freezing temperature — this is how the water manages to remain liquid at temperatures way below the normal freezing point of water.
The European Space Agency’s Mars Express has found several such underground ponds of perchlorate brine and now, a new study reports that these pockets of liquid water could be used to produce valuable resources.
Of course, you can’t drink salty water. You also can’t use it for too many things. If you want to apply the electrolysis to break it down into oxygen (for breathing) and hydrogen (for fuel), you’d normally need to remove the salt — a very costly and complicated process in the harsh Martian environment. This is where the research team led by Vijay Ramani from the University of Connecticut comes in.
Typically, electrolysis requires purified water, but Ramani’s research team found a way to apply electrolysis efficiently to extract hydrogen and oxygen out of the brine simultaneously, without needing to also extract the perchlorate.
“Our Martian brine electrolyzer radically changes the logistical calculus of missions to Mars and beyond” said Ramani. “This technology is equally useful on Earth where it opens up the oceans as a viable oxygen and fuel source”
They built a modular electrolysis system and tested it at -33 Fahrenheit (-36 Celsius), showing that it really does work. The fact that it’s modular means you can start a small operation on Mars (say, a small research base) and then build on it. Ironically, they were also able to use the salt in their favor.
“Paradoxically, the dissolved perchlorate in the water, so-called impurities, actually help in an environment like that of Mars,” said Shrihari Sankarasubramanian, a research scientist in Ramani’s group and joint first author of the paper.
“They prevent the water from freezing,” he said, “and also improve the performance of the electrolyzer system by lowering the electrical resistance.”
The results are so promising, researchers say, that they’re even considering using a similar technology here on Earth. For instance, submarines or deep-sea could make great use of this technology, potentially enabling us to explore uncharted environments in the deep ocean.
“Having demonstrated these electrolyzers under demanding Martian conditions, we intend to also deploy them under much milder conditions on Earth to utilize brackish or salt water feeds to produce hydrogen and oxygen, for example through seawater electrolysis,” said Pralay Gayen, a postdoctoral research associate in Ramani’s group and also a joint first author on this study.
NASA’s Perseverance rover, currently en-route to Mars, is also carrying some instruments that will allow it to produce oxygen from the Martian brine — but no hydrogen. Perseverance’s equipment is also 25 times less efficient than that designed in Ramani’s lab, but it will be a test for the technology and could perhaps offer new insights on how to apply the technology.
While a Martian base is probably pretty distant possibility, a lunar outpost is almost in sight. NASA has concrete plans to send humans back to the moon in this decade, and it wants to lay down infrastructure for a permanent research base. If this is successful, a Martian base might not be that far off.
The study “Fuel and oxygen harvesting from Martian regolithic brine” was published in PNAS.
A new study has revealed the detection of water in the upper atmosphere of Mars for the first time. The discovery gives scientists a good idea of the mechanism that is currently stripping the Red Planet of its water.
The surface of Mars is cold and dry —bereft of liquid water — but this wasn’t always the case. Studies of the Martian surface have discovered the tell-tale tracks of long dry ancient rivers and sedimentary deposits that indicate lake beds into which water once flowed. This poses the question of how the Red Planet lost its liquid water?
A study published in the journal Science suggests a new mechanism that could have driven Mars’ water loss. A team of astronomers has used data collected from Mars’ atmosphere by NASA’s Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution spacecraft (MAVEN) to discover water in the planet’s upper atmosphere.
“For the first time, we have seen water in the upper atmosphere of Mars, at around 150 km above the surface. Other scientists have previously observed water in the middle atmosphere,” Shane Wesley Stone, a PhD. Candidate in Planetary Sciences at the Lunar and Planetary Laboratory, University of Arizona, and one of the paper’s authors tells ZME Science. “Water in the upper atmosphere is quickly destroyed and can escape to space, which is why our observations of water in the upper atmosphere are significant.”
Water transported to the upper atmosphere of Mars is converted to atomic hydrogen, which is then so-light that it is lost to space. This process could have been driving Mars’ water loss for billions of years. Water had previously been detected in the lower atmosphere, where scientists believed it was confined, but this is the first detection of water in the upper atmosphere, which caught the team by surprise.
“We did not know that water makes it all the way to the upper atmosphere, so we did not know how important this upward transport of water is to the escape of hydrogen to space and thus to water lost from Mars,” Stone says, explaining that water higher in the atmosphere would be broken down much more rapidly than happens closer to the martian surface. “Water which makes it to the upper atmosphere is destroyed in about 4 hours. This destruction of water would be ten times slower in the middle atmosphere, where most of the products of this destruction would be transported downward back toward the surface.”
Rising Damp: How Does Water Make its Way to Mars’ Upper Atmosphere?
Stone explains that the team is not yet certain what processes are lifting water to Mars’ upper atmosphere, but their study has yielded some good clues as to what may be the major players in this phenomenon.
“We see a seasonal trend in the upper atmospheric water abundance,” says the planetary chemist. “During summer in the southern hemisphere, the water abundance in the upper atmosphere is largest. During summer in the northern hemisphere, the water abundance in the upper atmosphere is smallest but is still significant.”
Stone explains that this seasonal trend is caused by two things. Firstly, during southern summer, Mars is closer to the Sun than it is during the rest of the Martian year. Secondly, this is also the season of dust storms on Mars. He adds: “Relatively close proximity to the Sun and dust storms both lead to heating in the atmosphere, which leads to greater transport of water to the upper atmosphere.”
The researcher points to a massive Martian dust storm that occurred in 2018 as being a major contributing factor to water in the upper atmosphere. The storm was first spotted by NASA’s Mars Reconnaissance Orbiter (MRO) on May 30th 2018 and by June of that year, it had grown to a planet encompassing event.
“Dust storms lead to a sudden splash of water into the upper atmosphere: during the global dust storm of 2018, the water abundance in the upper atmosphere increases by 20x relative to the nominal seasonal abundance,” Stone says. “Smaller surges of water are observed during regional dust storms that occur every Mars year of 687 days. Global storms occur about once every 10 Earth years.”
The team believe that water is moving upward past what planetary scientists call the hygropause — a cold layer in the atmosphere at which water condenses from vapour to liquid, forming clouds. “This because, as we and other scientists have found, the Martian hygropause is not as efficient at trapping water close to the surface as the hygropause on Earth,” Stone says. “The hygropause on Mars is not as efficient because it is too warm: when Mars is closest to the Sun and when dust storms occur, heating caused by these processes warms the hygropause, allowing water to move upward.”
The mechanism their finding reveals is currently the main way that Mars loses water, but Stone points out that this likely wasn’t always the case.
The Changing Picture of Water Loss on Mars
Water transported to Mars’ upper atmosphere by seasonal effects and dust storms where it is broken down to hydrogen and then lost to space is currently the predominant mechanism of water loss on Mars, but the team says this is only because of the Red Planet’s current environment. The water loss mechanisms that have proceeded for billions of years were likely different in the past in terms of both dominance and the speed at which they proceed.
“This process we describe is an important factor in Martian water loss today. However, this water could only be transported to the upper atmosphere relatively recently, over the last billion years or so,” Stone says. “Much of Mars’ atmosphere was lost to space before this time, leading to the weak hygropause which allows water into the upper atmosphere. All escape processes we observe today were likely faster in the past.”
The team reached this conclusion due to the fact that when all the water loss rates of the present-day escape processes are summed, their current escape rate is too slow to explain all the water loss that scientists know must have occurred over the last few billion years.
“We know that over 4 billion years, Mars lost about 66% of its atmosphere to space,” Stone explains. “If we talk about water specifically, Mars has lost 10s to 100s of meters of a ‘global equivalent layer’ of water — equivalent to spreading all of the water lost by Mars over its surface to form an even layer and then reporting how deep this layer would be.”
The process the team describe is responsible for the loss of 44 cm of H2O over the last billion years, and global dust storms are responsible for the loss of an additional 17 cm on top of this over the last billion years.
“In the present epoch, during most of the Martian year, this process we describe is just as important as the ‘classical process’ — the basic process scientists thought responsible for the transport of hydrogen to the upper atmosphere since the first work on this topic in the early 1970s,” Stone says. “During global storms, this water which makes it to the upper atmosphere produces 10x more escaping hydrogen than does the classical process.”
Big Surprises and Future Investigations
Stone describes that the next steps for this research involve figuring out exactly how important this new water loss mechanism has been throughout the history of Mars.
“Extrapolating back over billions of years is extremely difficult and doing it correctly takes time. We still need to understand better the specific transport processes responsible for delivering this water to the upper atmosphere,” he says, adding that the team’s findings came as something as a shock even to them. “The entire project was a huge surprise to us: we were surprised to see water this high in the atmosphere, we were surprised to see the seasonal trend in the water abundance, and we were surprised by just how big an effect the global dust storm has on the upper atmospheric water abundance.”
Researching water loss from Mars is likely to be an important step in understanding how abundant water is throughout the Universe, as Dimitra Atri, a researcher from the Space Science at NYU Abu Dhabi (NYUAD), recently told ZME Science:“Since it is extremely difficult to observe the escape process in exoplanets, we are planning to study this phenomenon in great detail on Mars with the UAE’s Hope mission.”
Thus, this type of study could tell us how unique Earth is in terms of the possession of liquid water in the Universe. Something that could, in turn, tell us about the chances of life on exoplanets.
“Mars used to look like Earth: warmer and wetter with a thick atmosphere and abundant liquid water on its surface,” Stone concludes. “But over the history of the solar system, Mars’ water was lost to space, leaving behind the cold, dry, red planet we see today. Regardless, Mars will be the next planet on which humans step foot.”
Astronomers have found that Mars might have salty lakes sealed under its icy polar regions.
The low pressure that results from the lack of an atmosphere makes surface water on Mars impossible — unless it’s protected by something. That something, it turns out, exists; it lies on the Martian south pole, and you might know it as ice.
Astronomers first reported on the possibility of a subglacial lake on Mars back in 2018, and they just published a new paper admitting they were wrong. There’s not one lake on Mars, there’s several, and they’re salty — which makes them all all the more interesting for extraterrestrial life.
“We identified the same body of water, but we also found three other bodies of water around the main one,” says planetary scientist Elena Pettinelli at the University of Rome, who is one of the paper’s co-authors. “It’s a complex system.”
The discovery was made using a radar from the European Space Agency’s Mars-orbiting spacecraft Mars Express. The existence of the first lake was proposed after 29 observations made from 2012 to 2015. Now, the dataset includes 134 observations from 2012 to 2019 and makes a much stronger case for the existence of water on Mars. The first lake, observations suggest, is around 20 x 30 kilometers (12 x 18 miles), buried under 1.5 km (1 mile) of ice. Separate from the main lake, multiple bodies of water of various sizes are thought to exist.
These lakes are tantalizingly similar to subglacial lakes we have here on Earth such as Vostok Lake, although the Martian lakes are thought to be much saltier. In fact, the authors suggest that the liquid bodies are hypersaline solutions, which would explain why they can remain liquid despite the cold environment at the Martian pole. But even so it’s not implausible that they can support life.
A few billion years ago, Mars was warm and wet, much like Earth. But after its atmosphere slowly dissipated, Mars lost its water and turned into the dry desert we see today. However, there are still signs of water on the Red Planet.
Both satellite data and on-site analysis have supported the existence of former water bodies on Mars, this is the first time researchers have found solid evidence of actual bodies of water on Mars.
Whether this is an actual lake or something more akin to a sludge or slush is up for debate, and the lakes themselves are still debated. Jack Holt, a planetary scientist at the University of Arizona in Tucson, told Nature that he doesn’t think these are lakes.
So, for now, we’re left with a stronger, but still-not-fully-proven case for lakes on Mars. Thankfully, there may soon be additional data to help settle the debate. The Tianwen-1 mission will enter Martian orbit in February 2021, deploying a rover on its surface.
But it’s hard not to get excited at the possibility of liquid water on Mars because where water exists, life can also exist. If there really is life in these salty waters, it could take different forms, but it will almost certainly be microbial. Most scientists speculate that anaerobes (extremophile microorganisms that don’t need oxygen) are the most likely candidates, but the existence of oxygen-breathing microorganisms is also possible.
“The water bodies at the base of the (south polar layered deposits) therefore represent areas of potential astrobiological interest and planetary protection concern,” the study concluded, urging for more exploration studies to analyze these subglacial bodies.
Long before humans started erecting buildings, nature had its very own cement: precipitated minerals. Essentially, water rich in mineral components will gradually precipitate, forming precipitated rocks and minerals. These minerals are good indicators of the atmospheric conditions and water chemistry in which they were formed — somewhat as if they are keeping a geological diary of their forming conditions.
From the Martian orbit, researchers have observed a diversity of sulfate, carbonate and chloride salts — precipitated minerals which are excellent fingerprints for past environments. This would suggest that not only Mars had impressive surface lakes at some point in its surface, but that these were salty lakes. Now, researchers present new evidence to back this up — using data right from the Martian surface.
NASA’s Curiosity rover detected and analyzed salt-bearing sediments, confirming the existence of ancient salty lakes on Mars. Curiosity found traces of salts indicative of ancient brines — extremely saline waters which became more and more abundant as Mars entered its arid phase.
Curiosity is currently in Gale Crater, an ancient crater thought to be a former lake.
Interestingly, the salt minerals were not found in abundance in any other place that Curiosity analyzed, indicating that the layer in which the minerals were found represents a period of high salinity in the lake’s evolution — probably, as water evaporated and the salts concentrated.
William Rapin and colleagues report the detection of sulfate salts disseminated in sedimentary rocks, dating to around 3.3–3.7 billion years ago (the Hesperian time period). These salts were not found in such form and abundance in older rocks previously analysed by Curiosity. Thus, the researchers infer that the measurements are evidence of an interval of high salinity of the crater’s lake that may have occurred as the water evaporated. These findings support hypothesized fluctuations of the Martian climate during the Hesperian period.
It’s not the first time researchers have found clear clues of existing lakes and rivers on Mars. It is believed that during a period called the Hesperian (3.3 – 3.7 billion years ago), widespread volcanic activity and catastrophic flooding carved immense outflow channels across the surface of the Red Planet. Much of this water flowed to the northern hemisphere, where it probably began to pool, forming large transient lakes or potentially, an ice-covered ocean.
At some point, however, Mars became much drier. These recent findings are consistent with that hypothesis.
“Our findings support stepwise changes in Martian climate during the Hesperian, leading to more arid and sulfate-dominated environments as previously inferred from orbital observations,” the researchers conclude.
The study “An interval of high salinity in ancient Gale crater lake on Mars” has been published in Nature Geoscience.
Curiosity’s drilling instrument has gathered two samples from a Martian soil unit geologists called the “clay-bearing” unit. Worthy of its name, the unit turned out to contain a substantial amount of clay — a mineral typically formed in the presence of water.
The rover snapped this selfie after gathering the samples. To the lower-left of the rover are its two recent drill holes, at targets called “Aberlady” and “Kilmarie.” Image credits: NASA/JPL-Caltech/MSSS.
Although the Curiosity Rover was expected to run for two years, it’s still providing valuable information now, seven years after its landing in 2012. The rover is currently located on the side of lower Mount Sharp, in an area that drew the attention of NASA scientists even before Curiosity landed on Mars because it seemed to contain quite a lot of clay. Prosaically, they called it the “clay-bearing unit“.
However, prosaic or not, the name was very accurate. Curiosity harvested two small drills in the area, using its CheMin instrument (Chemistry and Mineralogy) to confirm that the unit has the highest amounts of clay minerals ever found on Mars.
This animation shows the initial proposed route for NASA’s Curiosity rover on Mount Sharp on Mars. The annotated version of the map labels different regions that scientists working with the rover would like to explore in the coming years. Image credits: NASA/JPL-Caltech/ESA/University of Arizona/JHUAPL/MSSS/USGS Astrogeology Science Center.
This strongly suggests that this area on Mount Sharp contained significant amounts of water. Clays typically form over long periods of time, through a process of weathering and accumulation of diluted solvents. Judging by the appearance and chemistry of this clay (which also includes very small amounts of hematite, an iron oxide that was abundant in the vicinity of the clay-bearing unit), it seems that these rocks formed as layers of mud in ancient lakes.
It’s not the first time Curiosity has found traces of ancient water on Mars. Time and time again, the rover has confirmed that water once flowed on Mars, sparking a heated debate about the possibility of microbial life on the Red Planet. Unfortunately, Curiosity is not well-equipped to look for signs of life so for now, that will remain a matter of speculation.
NASA’s Curiosity Mars rover imaged these drifting clouds on May 17, 2019, Image credits: NASA/JPL-Caltech.
After the analysis, the rover took a well-deserved rest, taking advantage of the moment using its black-and-white Navigation Cameras (Navcams) to snap images of drifting Martian clouds. NASA believes these are likely water-ice clouds — so Curiosity is not only finding water beneath the ground — it’s also finding it in the sky.
Water flew intermittently — but very intensely — on Mars, for billions of years.
A photo of a preserved river channel on Mars. Color shows different elevations (blue is low, yellow is high). Image credits: NASA/JPL.
The case for Mars having water in the past is already very strong, and this latest study brings even more evidence to support that idea. Mars is dry today but it used to have a thick atmosphere in the past and it could have supported liquid water. Remote sensing data has revealed numerous valleys which appear to be precipitation-fed former rivers.
Edwin Kite, Ph.D., first author of a new paper says that not only did Mars have rivers and lakes, but they were pretty big, and they were around for billions of years, over several geological periods.
Kite and colleagues used images from NASA’s Mars Reconnaissance Orbiter, characterizing over 200 such systems. They used the number of craters around to estimate the age of these rivers and used the visual data to calculate the intensity of the river runoff.
While some channels have eroded over the eons, many are still clearly visible due to the very slow erosion currently taking place on Mars. Ironically, the lack of water and atmosphere responsible for this slow erosion allowed researchers to better study these former rivers.
It’s unclear how deep these rivers were, but they were wide — on average, they were wider than those on Earth. They also appear to be evenly distributed across the Martian surface. The team’s results suggest that these rivers flower intermittently (probably fed by precipitations), but intensely.
“Using multiple methods, we infer that intense runoff production [..] persisted until <3 billion years (Ga),” researchers write in the study. “[The] precipitation-fed runoff production was globally distributed, was intense, and persisted intermittently over a time span of >1 Ga.”
There’s another interesting find: it’s not just that these rivers were active for billions of years, but they were active until the very period when Mars almost completely dried up.
“You would expect them to wane gradually over time, but that’s not what we see,” Kite said in a statement. “The wettest day of the year is still very wet.”
According to our current climate models of Mars, that just shouldn’t happen — there’s no way the thinning Martian atmosphere could have supported such rivers. It’s not clear where the problem lies, and it’s also not clear exactly when and why Mars dried up. Understanding that could offer us a new understanding of whether Mars what habitable.
“Our work answers some existing questions but raises a new one,” Kite said in the statement. “Which is wrong: the climate models, the atmosphere evolution models or our basic understanding of inner solar system chronology?”
The Curiosity Rover currently roaming Mars and NASA’s upcoming 2020 Mars rover will probably offer crucial puzzle pieces to solve that question — and more.
The study “Persistence of intense, climate-driven runoff late in Mars history” has been published in Science Advances.
These rocks are a good indicator that water once flowed on Mars.
NASA’s Mars rover Curiosity acquired this image using its Mars Hand Lens Imager (MAHLI), located on the turret at the end of the rover’s robotic arm, on March 24, 2019, Sol (day) 2356 of the Mars Science Laboratory Mission. Image credits: NASA/JPL-Caltech/MSSS.
The images that Curiosity and the other Mars Rovers sent back to Earth have been nothing short of amazing. They’ve offered us a breathtaking window into a planet which shares both striking similarities and dramatic differences to our Earth. But generally, these pictures have one thing in common: they’re clearly from Mars. The image above, in contrast, looks like it could have been snapped from most rivers on Earth.
A few things are intriguing in this image. For starters, the rocks seem a bit paler than the usual rust-red we’re used to seeing on Mars. Secondly, the rocks are rounded off as if they are river rocks — and to top it all off, there’s a couple of strangely-looking spherical white-ish rocks which you just wouldn’t imagine on Mars.
While NASA says these are almost certainly not river rocks, they still hint at Mars having a wet past.
These rounded rocks are formed through a phenomenon called concretion. Concretionary rocks are quite common on Earth: they form in water-rich environments, hardening over time. A concretion is formed by the precipitation of mineral cement within the spaces between particles and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur.
This type of rocks are very susceptible to erosion (not necessarily water erosion), and the outer layers erode faster than the inner ones, leaving behind the rounded shapes we see here.
It’s a fantastic reminder that the geological processes we are so familiar with here on Earth are also often present on other bodies — and at least in some ways, Mars is very much like the Earth.
A self-portrait of the Curiosity Mars rover on Vera Rubin Ridge, which it’s been investigating for the past several months. Directly behind the rover is a clay-rich slope scientists are eager to begin exploring. Image credits: NASA/JPL-Caltech/MSSS.
The Curiosity Rover is earning its keep, sending back more and more valuable information about the Red Planet.
A rendering of Gale Crater, with Mount Sharp at its center. The Curiosity rover is currently exploring this area, trying to find whether Mars could have supported life. Image credits: NASA.
When researchers and engineers decided to land Curiosity inside Gale Crater, they didn’t choose randomly. The crater, which contained a massive lake, was chosen because due to its structure, there’s a good chance of learning many of Mars’ geological secrets. While it was already established that Mars held water, the conditions of the water and the overall environment is still unclear. Now, this research shows that not only was the planet hosting a lot of water — it had lakes much like those on Earth.
Geochemist Joel Hurowitz from Stony Brook University led a large team that analyzed over 100 meters of rock layers in Gale Crater. To reconstruct the past environment, they measured the aluminum inside each layer, plotting it against minerals like sodium and calcium, which easily leach out of the rock. Basically, warm water is more chemically active than cold water. During warm conditions, water is better at dissolving and absorbing stuff (just like how sugar melts easier in hot water). In this case, if a rock has a lot of aluminum but not so much sodium or calcium, it indicates that it formed in a warmer environment.
Oxygen was another key component they looked at. There are sharp differences between deeper and more shallow water, in terms of oxygen content. By adding the oxygen content into the mix, researchers were able to show that the lake was a diverse feature, much like those on Earth. These conditions also apparently lasted for a very long time: some 700 million years!
“These were very different, co-existing environments in the same lake,” said Joel Hurowitz of Stony Brook University, lead author of the report. “This type of oxidant stratification is a common feature of lakes on Earth, and now we’ve found it on Mars. The diversity of environments in this Martian lake would have provided multiple opportunities for different types of microbes to survive.”
“This is a new level of detail in terms of our understanding of the chemical environment in this lake on Mars,” Hurowitz added. “It gives us a much more complete picture of the habitability of this lake.”
A simulation depicts a lake partially filling Mars Gale Crater. Illustration: NASA / JPL-Caltech.
We still don’t know if Mars did have any life (and if it did, we shouldn’t get our hopes up for anything bigger than microbial), but having a complex lake system, with warm water ranging from shallow to deep is definitely exciting. It means it could have supported several different types of microbes. Some microbes thrive in low-oxygen environments, while other prefer the opposite. Keep in mind that scientists are looking into a time when photosynthesis hadn’t even evolved on Earth, so we’re not sure what kind of microbial life Mars might have hosted.
“We’re learning that in parts of the lake and at certain times, the water carried more oxygen,” said Roger Wiens, a planetary scientist at Los Alamos National Laboratory and co-author of the study, published today in the journal Science. “This matters because it affects what minerals are deposited in the sediments, and also because oxygen is important for life. But we have to remember that at the time of Gale Lake, life on our planet had not yet adapted to using oxygen–photosynthesis had not yet been invented. Instead, the oxidation state of certain elements like manganese or iron may have been more important for life, if it ever existed on Mars. These oxidation states would be controlled by the dissolved oxygen content of the water.”
A drilled hole made by Curiosity. Image credits: NASA / JPL.
Researchers were surprised by the accuracy of the Curiosity analysis, and how much we can deduct from that. But put together, this makes a lot of sense.
“What was causing iron minerals to be one flavor in one part of the lake and another flavor in another part of the lake?” Hurowitz asked. “We had an ‘Aha!’ moment when we realized that the mineral information and the bedding-thickness information mapped perfectly onto each other in a way you would expect from a stratified lake with a chemical boundary between shallow water and deeper water.”
A hypothesized model of a redox-stratified lake in Gale crater — just like a lake on Earth. Source: NASA / JPL.
In total, Curiosity has been on Mars for over 1,700 sols (martian days, which are 24 hours, 39 minutes long), traveling 16 km from the bottom of Gale Crater towards the peak of Mount Sharp. Its main objective is determining whether Mars could have supported life, by analyzing nature and inventory of organic carbon compounds, investigating the chemical components which could serve as the building blocks of life, identifying biosignatures of life, investigating the chemical, isotopic, and mineralogical composition of the Martian surface, interpreting geological processes taking place and assessing the broad spectrum of surface radiation, which is necessary for a future manned mission to Mars.
As for whether Mars does host life now, unfortunately, that’s not an answer Curiosity is equipped to answer. We’ll have to wait a few more years for NASA’s next Mars mission to figure that one out.
Journal Reference: J. A. Hurowitz et al — Redox stratification of an ancient lake in Gale crater, Mars. DOI: 10.1126/science.aah6849
New evidence in support of the oceans-on-Mars theory has surfaced from a very spectacular source: geological deposits associated with tsunamis have been mapped on the red planet.
Image credits Aynur Zakirov.
Scientists are fairly certain that at some point in the past, Mars held liquid water. But a more controversial topic is how much of it there was — namely, if Mars ever had oceans on its surface. A new paper published by an international team of researchers comes to support the idea that oceans did in fact once grace the face of Mars in style: with tsunamis.
“We found typical tsunami deposits along the dichotomy between the northern hemisphere and southern hemisphere of Mars, it supports that there was, at that time, a northern ocean,” Francois Costard, PhD, researcher at the Université Paris-Sud 11, Orsay Earth Science Department and director of research at the French National Center for Scientific Research (CNRS) and first author of the paper said of the sediment distribution on the northern plains of Mars.
These structures are known as lobate flow deposits and were first sighted by the Viking orbiters in the early days of martian research. They’re basically piles and piles of large rocks and other geological debris stacked below cliffs, with characteristic shape and topography. The deposits in the area the team was investigating (Vastitas Borealis Formation) were previously theorized to have been formed by mud volcanoes, glacier movement, or mud flows.
But the characteristics displayed by the lobade deposits are suspiciously similar to what you’d expect to see when a tsunami hits high-land and all the stuff it’s been moving anchors itself on the terrain.
“These lobate deposits propagate uphill from the northern plains and do so in close association with a potential palaeo-shoreline,” explains co-author Stephen Clifford from the Lunar and Planetary Institute in Houston, Texas.
“The predictions of the numerical modelling that François and his colleagues have done provide a very persuasive case for an ocean at this time. There’s also a second set of landforms that we see along the coastline called thumbprint terrain […] the reflection of the tsunami waves from the coast and their interaction with a second set of tsunami waves, predicted by the numerical modelling, would have resulted in sediment deposition that’s very similar to what we actually observe on Mars.”
The team believes the tsunami originated in what today is the Lomonsov crater in Mars’ Norther District, generated after a massive meteorite impacted in the middle of the ocean. The team believes waves as high as 150m followed the impact — suggesting that there was ample free water to be stirred by the asteroid, which can only mean an ocean.
(A) Thumbprint terrain showing a curving pattern of high-albedo mounds, low-albedo flat surfaces and terminal lobate deposits (black arrow.) (B) Study area. (C) Detail of convex pattern of the thumbprint terrain from (A) (black arrows indicating flow directions). Image credits Francois Costard et al., 2017, JGR.
The Lomonsov crates is a 120km-wide bowl named for 18th century Russian polymath Mikhail Vasilyevich Lomonosov. Its size suggests a very powerful impact, and the team believes it created two sets of waves. This first wave was an estimated 300m in height, and likely reached the paleo-shoreline of hills and plateaus in a matter of hours, depositing the lobate flows.
“It was a really large-scale, high speed tsunami. At the very beginning, a crater of 70km in diameter was created by the impact. This expelled a huge volume of water, with wave propagation at 60m/second,” Clifford adds.
Clifford says that the main takeaway from the research is that there was likely a large amount of liquid water to be found on the Martian surface of old, which “[has] implications for the total inventory of water on Mars.”
It’s likely that oceans housed the earliest of Earth’s life, so finding one on Mars would definitely improve the chances of life (at least, life as we know it) developing on the planet. And if there was once abundant water on our red neighbor, maybe it found a way to hold on until today.
The paper “Modeling tsunami propagation and the emplacement of thumbprint terrain in an early Mars ocean” has been published in the Journal of Geophysical Research.
The Curiosity Rover has found boron on the surface of Mars – a strong indication that the Red Planet once hosted long-term habitable groundwater, making it even more likely that life once existed on Mars.
ChemCam target Catabola is a raised resistant calcium sulfate vein with the highest abundance of boron observed so far. The red outline shows the location of the ChemCam target remote micro images (inset). The remote micro images show the location of each individual ChemCam laser point (red crosshairs) and the B chemistry associated with each point (colored bars). The scale bar is 9.2 mm or about 0.36 inches. Credit: JPL-Caltech/MSSS/LANL/CNES-IRAP/William Rapin
The exciting discovery was announced at the American Geophysical Union conference. Because boron is associated with arid sites where much water has evaporated away, the perspectives are obviously intriguing.
“No prior mission to Mars has found boron,” said Patrick Gasda, a postdoctoral researcher at Los Alamos National Laboratory.
Here on Earth, similar traces can be found in California or other arid areas which were once rich in water. If this is also the case on Mars, then everything would align to make Mars suitable for extraterrestrial life.
“If the boron that we found in calcium sulfate mineral veins on Mars is similar to what we see on Earth, it would indicate that the groundwater of ancient Mars that formed these veins would have been 0-60 degrees Celsius [32-140 degrees Fahrenheit] and neutral-to-alkaline pH.” The temperature, pH, and dissolved mineral content of the groundwater could make it habitable.
The environmental implications of the boron and how exactly it came to be is still a matter of debate. It could be that the drying out of a lake resulted in a boron-containing deposit in an overlying layer, not yet reached by Curiosity. Some of the material from this layer could have later been carried by groundwater down into fractures in the rocks. Yet it could also be that the chemistry of clay-bearing deposits and groundwater affected how boron was picked up and dropped off within the local sediments. Either way, while there is still some debate going on, the evidence seems to indicate to a water-rich past, and one that could support life.
This type of active groundwater acts like a chemical reactor in a way. It dissolves old minerals, creates new ones, and generates a redistribution of electrons – all reactions which support the emergence of life. These dynamic processes are visible in the mineral veins that filled cracks in older layered rock. But this also affected the composition of that rock matrix surrounding the veins, and the fluid was in turn affected by the rock.
“There is so much variability in the composition at different elevations, we’ve hit a jackpot,” said John Grotzinger, of Caltech, Pasadena, Calif. As the rover gets further uphill, researchers are impressed by the complexity of the lake environments when clay-bearing sediments were being deposited and also by the complexity of the groundwater interactions after the sediments were buried.
The discovery of boron is just one of several exciting findings on Mars, but at the moment, we still don’t know for sure whether life did exist on Mars. The circumstantial evidence is strong, but at the end of the day, it’s still circumstantial evidence. But the stars are starting to align, and the future might hold some interesting things.
Mars is now a cold and dry place, but it wasn’t always like this – the Red Planet used to have a lot of water on its surface. Now, researchers have discovered one of the very last places where (potentially habitable) liquid water existed.
This is a perspective rendering of the Martian chloride deposit. Credit: LASP / Brian Hynek
Water on Mars exists today almost exclusively as ice, with a small amount present in the atmosphere as vapor. The only place where water ice is visible at the surface is at the north polar ice cap. But even today, we still see clear evidence that the planet was once a wet place. Researchers from the University of Colorado Boulder have identified and analyzed such a place – a salt flat which was once a lake.
Salt flats here on Earth are not especially uncommon. Natural salt pans or salt flats are flat expanses of ground covered with salt and other minerals which usually form when salty water pools evaporate. Based on the surface and apparent thickness of the salt, researchers estimate that the lake was about 8% as salty as Earth’s oceans – which means it was quite hospitable for microbial life.
“By salinity alone, it certainly seems as though this lake would have been habitable throughout much of its existence,” Brian Hynek, a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU-Boulder and lead author of the study.
However, other relevant factors for habitability such as acidity were not the scope of the study and were not considered here – in fact, the potential habitability of the lake was not explored at all.
But what’s interesting about this formation is its age: digital terrain mapping and mineralogical analysis of the features surrounding the deposit indicate that the former lake bed is no older than 3.6 billion years ago – which means that it hosted water for a very long time, and was one of the last watery places on Mars.
“This was a long-lived lake, and we were able to put a very good time boundary on its maximum age,” said Hynek, who is also an associate professor in the Department of Geological Sciences at CU-Boulder and director of the CU Center for Astrobiology. “We can be pretty certain that this is one of the last instances of a sizeable lake on Mars.”
Brian M. Hynek, Mikki K. Osterloo, Kathryn S. Kierein-Young. Late-stage formation of Martian chloride salts through ponding and evaporation. Geology, 2015; G36895.1 DOI: 10.1130/G36895.1
Researchers have long known that Mars has water on its surface in the form of ice, but now, after years and years of research, we might finally have the decisive clue that our planetary neighbor has liquid water on its surface. The key find was perchlorate – a substance that significantly lowers the freezing point, so that water doesn’t freeze into ice, but remains liquid and briny.
Image credits University of Copenhagen.
“We have discovered the substance calcium perchlorate in the soil and, under the right conditions, it absorbs water vapour from the atmosphere. Our measurements from the Curiosity rover’s weather monitoring station show that these conditions exist at night and just after sunrise in the winter,” explains Morten Bo Madsen, associate professor and head of the Mars Group at the Niels Bohr Institute at the University of Copenhagen.
Perchlorates are substances which can be produced naturally and are soluble in water. Basically, if you mix them with water, the freezing temperature of water significantly; in other words, it can get a lot colder without the water actually freezing – it becomes a sort of liquid brine. The situation on Mars is especially fit to accommodate this mixture, as researchers explain. This can also explain some of the water circulation on the Red Planet.
“When night falls, some of the water vapour in the atmosphere condenses on the planet surface as frost, but calcium perchlorate isvery absorbent and it forms a brine with the water, so the freezing point is lowered and the frost can turn into a liquid. The soil is porous, so what we are seeing is that the water seeps down through the soil. Over time, other salts may also dissolve in the soil and now that they are liquid, they can move and precipitate elsewhere under the surface,” Madsen adds.
The Curiosity Rover has previously found tantalizing clues that water once flowed on Mars. It is now believed that Mars kept its liquid water for millions of years – it also has the rounded rocks with the right chemistry to boast. But if there are indeed large quantities of perchlorate on the surface, it might mean that liquid water on Mars (or right below its surface) is much more common than previously thought.
Close-up observations have also shown characteristic of old riverbeds with rounded rocks, as well as expanses of sedimentary deposits, lying as ‘plates’ one above the other and leaning a bit toward Mount Sharp. The latter are very typical types of deposits, related to lake environments:
“These kind of deposits are formed when large amounts of water flow down the slopes of the crater and these streams of water meet the stagnant water in the form of a lake. When the stream meets the surface, the solid material carried by the stream falls down and is deposited in the lake just at the lakeshore. radually, a slightly inclined slope is built up just below the surface of the water and traces of such slanting deposits were found during the entire trip to Mount Sharp. Very fine-grained sediments, which slowly fell down through the water, were deposited right at the very bottom of the crater lake. The sediment plates on the bottom are level, so everything indicates that the entire Gale Crater may have been a large lake,” Madsen continues.
A long long time ago, some 4.5 billion years ago, Mars would have been a very different place than it is today – with a solid atmosphere and a lot of liquid water. But the atmosphere has dissipated into space, the water has also evaporated and escaped the planet and Mars no longer has a magnetic field.
So what does this mean for the possibility of finding life on Mars? Well, even though water is an essential requirement for life as we know it, water itself is not sufficient. Mars is really cold, and not protected from cosmic radiation (like Earth is), so finding life is not as likely as you’d be tempted to think. But it’s still a possibility.
Intricate polygons on Mars could be a clear indication of a wet past for the Red Planet. Most crater floor polygons have diameters ranging from 15 to 350 m, and it’s still not clear how and why they appeared – though one theory seems to be gaining ground: the idea of former lake beds.
Image 1. Typical crater floor polygons. [A] CTX (a 6 meter/pixel camera onboard the Mars Reconnaissance Orbiter, P16_007372_2474).of a 14 km‐sized impact crater
Polygons are some of the most common features at high latitudes on Mars. They have been observed by both lander and orbiting spacecraft. They range in size from 2 m all the way up to 10 km, and there is still an ongoing debate regarding their formation. Proposed mechanisms include thermal contraction, desiccation, volcanic, and tectonic processes; the polygons also bear similar resemblance to polygons observed on Earth, which took shape on the seafloor.
In 2000, an analytical model based on fracture mechanics (El Maarry et al., 2010) showed that through thermal changes alone (no water), the maximum fracture spacing attainable is 75 meters, with more probable values revolving around 20 meters – so this is clearly not the cause here. Also, no exact tectonic processes which can cause such formations have been identified – so the only plausible possibility left is a former sea floor.
On Earth, polygon-shaped areas, with the edges formed by faults, are common in fine-grained deep-sea sediments. Some of the best examples of these polygon-fault areas are found in the North Sea and the Norwegian Sea. We know this because the areas have been thoroughly surveyed through seismic techniques for offshore oil and gas deposits. While they are diverse and intricate, all polygons seem to have one thing in common – form in a common environment: sediments made up of fine-grained clays in ocean basins that are deeper than 500 meters, and when these sediments are only shallowly buried by younger sediments. The slope angle of the seafloor also plays a crucial role: when the slope is very gentle (or non existent), the shape of the polygons tends to remain unchanged. However, when there is some positive or negative topography, the shapes are often altered or broken down.
So if this is indeed the case on Mars (and there’s little reason why it shouldn’t be), it seems pretty clear that we’re dealing not only with a water body, but with a water body which was at least half a kilometer deep. Furthermore, the variation of crater floor polygons sizes with location can be indicative of different hydrologic environments. So not only was there likely water on Mars – but it was likely a big and complex system.
Researchers have reported dark streaks near the equator of Mars, hinting at surprisingly large quantities of flowing water. If true, this could be extremely important for life on Mars, and potentially even establishing research bases.
Water on Mars – yes
If you don’t know that rivers and lakes were fairly common on Mars a long time ago, you haven’t been reading a lot of ZME Science. We’ve written tons of articles about water on Mars, with information coming most notably from the Curiosity Rover, Opportunity Rover, and from interpreted pictures. With the development of technology it became fairly simple to observe the river-like valleys which attest almost beyond the shadow of a doubt the flow of water on ancient Mars. However, the planet has changed dramatically in the past billion years (hey, who hasn’t?).
Today, the atmosphere is too thin to support liquid water on the surface for long. However, there are things which suggest that water may still run on the surface from time to time. The first clear signs that this was happening occurred in 2011, when the Mars Reconnaissance Orbiter (MRO) spacecraft observed dark streaks a few metres wide that popped up and widened during the warm season, only to shrink in cooler seasons. The same cycle was observed up to the end of 2013.
“This behaviour is easy to understand if these are seeps of water,” says planetary scientist Alfred McEwen of the University of Arizona in Tucson, who led that study. “Water will darken most soils.”
The streaks were observed in seven different points, located in the relative proximity of the Martian equator. They probably came from the ice trapped about a metre below the surface; the MRO has in fact spotted fresh water occurring following meteoric impacts, which seems to support this theory.
Life on Mars? Probably
Now, McEwen and his colleagues have found 12 more sites; just so you can make an idea, each site has hundreds or thousands of such streaks. The interesting thing is the source. The temperatures there are relatively warm throughout the year, so without a constant source, the subsurface ice would probably already have sublimated. So where does the ice/water come from?
His theory is that water may come from groundwater deep in the crust, which, if true, has major implications for life on Mars – basically, there’s no good reason why life shouldn’t exist in the Martian underground.
“The subsurface is probably the best place to find present-day life if it exists at all because it is protected from the radiation and temperature extremes,” he says. “Maybe some of that water occasionally leaks out onto the surface, where we could see evidence for that subsurface life.”
Hard to explore
However, even if this is the case, it will be extremely hard to explore these areas, as any spacecraft has to be sterilized extremely carefully, to prevent the possibility of contamination.
“You wouldn’t want to send a dirty spacecraft to these places because you’d have the potential to not discover what you’re looking for, but what you took with you,” says John Rummel, chair of COSPAR’s panel on planetary protection.
But it’s not as simple as rubbing the shuttle with alcohol – the sterilization process is very complicated, including heat, hydrogen peroxide vapour or ionizing radiation to kill off as much Earth life as possible. This would significantly raise the costs of any mission in any of those areas.
NASA’s Curiosity rover has come up with yet another remarkable discovery – evidence of an ancient, freshwater lake, with water that was likely very similar to that of today’s Earth lakes. The feature is thought to be part of a longstanding aquatic environment which could have supported simple life forms.
This illustration depicts a concept for the possible extent of an ancient lake inside Gale Crater. Image Credit: NASA/JPL-Caltech/MSSS
“In March, we did know that we had a lake, but what we weren’t sure of was how big it was and how long it lasted, and also we were not sure about the broader geological context that supports the presence of lakes coming and going for a very long time,” said John Grotzinger – a Caltech planetary geologist who is the chief scientist of the Curiosity rover missionsaid in an interview. He is the author of the scientific paper called “A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars.”
“This is really similar to an Earth environment,” he said at the AGU news conference.
Scientists have known for a while that in its earlier days, Mars looked a lot more like the Earth than it does now. There have been several clear indications of water on Mars, but this is the best evidence yet that Mars had swimming holes that stuck around for thousands or perhaps millions of years. It was almost certainly very cold, but still habitable. The former lake’s size was comparable to that of the New York finger lakes – approximately 40 km in length and less than 10 in width. The freshwater may have sometimes frozen over, but the research shows that the lake was not some momentary feature, but rather was part of a long-lasting habitable environment that included rivers and groundwater – very favorable conditions of supporting life.
“If we put microbes from Earth and put them in this lake on Mars, would they survive? Would they survive and thrive? And the answer is yes,” said Grotzinger.
Curiosity on Mars: The rover nears a ridge named “Cooperstown,” a possible site for contact inspection with tools on the robotic arm. Credits: NASA.
However, Curiosity won’t be able to provide more information on the potential (former) habitability of the lake bed. If microorganisms did inhabit the lake, it’s likely that they greatly resemble chemolithoautotrophs – mineral eaters which typically thrive in exotic environments such as caves or deep sea underwater vents – and Curiosity lacks the tools to answer these issues.
But researchers are hyped about this discovery nonetheless.
“I’m most excited about the nature of the water,” said Jim Bell, an Arizona State University scientist who has worked with the cameras on Curiosity as well as two precursor rovers, Spirit and Opportunity, and is a co-author of four of the new papers. “Previous results from Spirit and Opportunity pointed to very acidic water, but what we’re seeing in Gale Crater is evidence of fresh water. Very neutral. Drinkable.”
In the time it has spent on the Red Planet, the brave rover has provided incredibly valuable information. In a little more than a year on the Red Planet, the mobile Mars Science Laboratory has determined the age of a Martian rock, found evidence the planet could have sustained microbial life, taken the first readings of radiation on the surface, and shown how natural erosion could reveal the building blocks of life.
A study conducted by researchers from the Carnegie Institution for Science concluded that both Earth and Mars got their water from the same source chondritic meteorites. However, unlike Earth, Martian rocks containing atmospheric volatiles such as water don’t get recycled into the planet’s deep interior.
The origin, history, and evolution of Martian water are pretty much a hot topic of debate. Although the Red Planet’s canals practically scream “we had water”, that terrain is pretty ancient, so while early Mars might have been all warm and wet, not, it’s just cold and dry.
Researchers analyzed water concentrations and hydrogen isotopic compositions trapped inside crystals within two Martian meteorites known as shergotites; one of the meteorites was rich in rich in elements such as hydrogen, and the other depleted. The two meteorites, pristine samples of various Martian volatile element environments, contain trapped basaltic liquids. However, the rich one of them has a hydrogen isotopic composition similar to that of Earth, and it appears to have changed little on its way from the Martian mantle up to the surface of Mars. The other one, however, appears to have sampled Martian crust that had been in contact with the atmosphere. So one of them had samples from the deeper parts, when Mars originally formed and had water, and the other one resembled recent Mars, with a dry environment.
“There are competing theories that account for the diverse compositions of Martian meteorites,” says researcher Tomohiro Usui. “Until this study there was no direct evidence that primitive Martian lavas contained material from the surface of Mars.”
“The hydrogen isotopic composition of the water in the enriched meteorite clearly indicates that they have been overprinted, so this meteorite tells scientists more about the Martian crust than about the Martian mantle,” he added. “Conversely, the other meteorite yields more information about the Martian interior.”
Since the hydrogen isotopic concentration was very different, the team believes that Martian surface water has had a different geologic history than water from the interior. The concentration of pure water are also very different – one of them had 10 times more water than the other one, so it’s becoming increasingly clear that Mars had two different stages in its evolution.
“To understand the geologic history of Mars, more information about both of these environments is needed,” Carnegie’s Conel Alexander said.
Several studies performed in the last decade have shown Mars used to be warmer and wetter, but scientists still haven’t figured out exactly why we are seeing these clues and how our red neighbor used to look like ages ago. Now, a new study concluded that Mars was much, much wetter than previously believed and that its atmosphere was significantly thicker as well.
The Early Mars atmosphere was about 20 times thicker than it is now, at least according to Georgia Tech Assistant Professor Josef Dufek. Currently, the atmosphere on Mars is about 1 percent as dense as that on the Earth, and liquid water can’t last long (if at all), on the surface. However, there are some which believe there is ice, and perhaps even liquid water beneath the surface.
“Atmospheric pressure has likely played a role in developing almost all Mars’ surface features,” he said. “The planet’s climate, the physical state of water on its surface and the potential for life are all influenced by atmospheric conditions.”
His first research tool was a rock fragment shot into the Martian atmosphere during a volcanic eruption some 3.5 billion years ago. The rock landed in the volcanic sediment, creating what is called a divot (or bomb sag), eventually solidifying in the same area. His next tool was, of course, the Mars rover Spirit. In 2007, Spirit landed at that site, known as Home Plate, and took a closer look at the imbedded fragment. Dufek and colleagues received enough data to determine the shape, size and depth of the bomb sag, enabling them to find out enough to make their own bomb sags – which they did.
They hit the lab and created sand beds using the same grain size as the one observed by Rover in that spot. The team then propelled various materials (glass, various rocks, even steel) at different speeds into dry, saturated and damp sand beds, comparing the resulting divots with the one observed on Mars. By varying the speeds, they found out that the rock hit the sand at a speed just under 40 meters per second, and in order for a rock like that to move through the atmosphere at that peak velocity, the atmosphere would have to be about 20 times thicker than it is today.
But perhaps even more interesting was the fact that no matter the type of the particle, the only times the lab bomb sag looked like the real one was when the sand was water saturated.
“Our study is consistent with growing research that early Mars was at least a transiently watery world with a much denser atmosphere than we see today,” said Dufek. “We were only able to study one bomb sag at one location on the Red Planet. We hope to do future tests on other samples based on observations by the next rover, Curiosity.”