In the coming decades, NASA and China intend to send the first crewed missions to Mars. Given the distance involved and the time it takes to make a single transit (six to nine months), opportunities for resupply missions will be few and far between. As a result, astronauts and taikonauts will be forced to rely on local resources to meet their basic needs – a process known as in-situ resource utilization (ISRU). For this reason, NASA and other space agencies have spent decades scouting for accessible sources of liquid water.
Finding this water is essential for future missions and scientific efforts to learn more about Mars’s past, when the planet was covered by oceans, rivers, and lakes that may have supported life. In 2018, using ground-penetrating radar, the ESA’s Mars Express orbiter detected bright radar reflections beneath the southern polar ice cap that were interpreted as a lake. However, a team of Cornell researchers recently conducted a series of simulations that suggest there may be another reason for these bright patches that do not include the presence of water.
In two days (on Thursday, Feb. 18th, 2021), NASA’s Perseverance rover will land on Mars. As the latest robotic mission in the Mars Exploration Program (MEP), Perseverance will follow in the footsteps of its sister mission, Curiosity. Just in time for its arrival, research conducted at the Southwest Research Institute (SwRI) has shown that Mars’ surface was shaped by flowing water several million years earlier than previously thought.
Radar data collected by ESA’s Mars Express point to a pond of liquid water buried under layers of ice and dust in the south polar region of Mars. Credit: ESA
Evidence of Mars’ watery past is written all over the surface of the planet. Between dried-up river valleys, outflow channels, and sedimentary deposits, it is clear that Mars was once a much different place. But until recently, the mystery of where this water went has remained unsolved. This changed in 2018 when data obtained by the ESA’s Mars Expressprobe indicated the existence of water beneath the south pole of the planet.
According to the Mars Express probe’s Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), this body of water is in a 20 km (~12.5 mi) wide area about 1.5 km (~1 mi) beneath the surface. And now, further analysis of the data by a team led by the Roma Tre University has revealed the existence of three new ponds, the largest of which measures about 20 x 30 km (~12.5 x 18.5 mi) and is surrounded by many smaller ponds.
This low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin" on lower Mount Sharp. Credits: NASA/JPL-Caltech/MSSS
Ever since Curiosity landed on Mars in 2012, the rover has made numerous groundbreaking discoveries about the Red Planet. These include confirming how Mars once had flowing water and lakes on its surface, evidence of how it lost its ancient atmosphere, and the discovery of methane and organic molecules. All of these discoveries have bolstered the theory that Mars may have once supported life.
The latest discovery came on Thursday, May 7th, when NASA announced that the Curiosity rover had once again discovered organic molecules. This time, however, the molecules were found in three-billion-year-old sedimentary rocks located near the surface of lower Mount Sharp. This evidence, along with new atmospheric evidence, are another indication that ancient life may have once existed on the Red Planet.
MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity since it landed in 2012. Credits: NASA/JPL, illustration, T.Reyes
As Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA Headquarters, explained in a recent NASA press release:
“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life. I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”
In the first paper, the authors indicate how Curiosity’sSample Analysis at Mars (SAM) suite detected traces of methane in drill samples it took from Martian rocks. Once these rocks were heated, they released an array of organics and volatiles similar to how organic-rich sedimentary rocks do on Earth. On Earth, such deposits are indications of fossilized organic life, which may or may not be the case with the samples examined by Curiosity.
However, this evidence is bolstered by the fact that Curiosity has also found evidence that the Gale Crater was once an ancient lakebed. In addition to water, this lakebed contained all the chemical building blocks and energy sources that are necessary for life. As Jen Eigenbrode of NASA’s Goddard Space Flight Center, and the lead author of the first study, explained:
“Curiosity has not determined the source of the organic molecules. Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in materials holds chemical clues to planetary conditions and processes… The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter. Finding ancient organic molecules in the top five centimeters of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper.”
This image illustrates possible ways methane might get into Mars’ atmosphere and also be removed from it. Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan
In the second paper, the team described how Curiosity’s SAM suite also detected seasonal variations in methane in the Martian atmosphere. These results were obtained over the course of nearly three years on Mars, which works out to almost six Earth years. While the team admits that water-rock chemistry could have generated the methane, they cannot rule out the possibility that it was biological in origin.
In the past, methane and organic molecules have been detected in Mars’ atmosphere and in drill samples, the former of which appeared to spike unpredictably. However, these new results indicate that within the Gale Crater, low levels of methane peak during the warm summer months and drop in the winter months every year. As Chris Webster, a researcher from NASA’s Jet Propulsion Laboratory (JPL) and the lead author of the second paper, explained:
“This is the first time we’ve seen something repeatable in the methane story, so it offers us a handle in understanding it. This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.'”
To find this organic material, Curiosity drilled into sedimentary rocks (known as mudstone) in four areas in the Gale Crater. These rocks formed over the course of billions of years as sediments were deposited at the bottom of the ancient lake by flowing water. The drill samples were then analyzed by SAM, which used its oven to heat the samples to over 500 °C (900 °F) to release organic molecules from the powdered rock.
Simulated view of Gale Crater Lake on Mars. This illustration depicts a lake of water partially filling Mars’ Gale Crater, receiving runoff from snow melting on the crater’s northern rim. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS
These results indicate that some of the drill samples contained sulfur (which could have preserved the organic molecules) as well as thiophenes, benzene, toluene, and small carbon chains – such as propane or butene. They also indicated organic carbon concentrations of about 10 parts per million or more, which is consistent with carbon concentrations observed in Martian meteorites and about 100 times what has been previously detected on Mars’ surface.
While this does not constitute evidence of past life on Mars, these latest findings have increased confidence that future missions will find more organics, both on the surface and slightly beneath the surface. But above all, they have bolstered confidence that Mars may have once had life of its own. As Michael Meyer, the lead scientist for NASA’s Mars Exploration Program, summarized:
“Are there signs of life on Mars? We don’t know, but these results tell us we are on the right track.”
In the coming years, additional missions will also be searching for signs of past life, including NASA’s Mars 2020 rover and the European Space Agency’s ExoMars rover.The Mars 2020 rover will also leave samples behind in a cache that could be retrieved by a future crewed mission for sample-return analysis. So if there was life on Mars (or, fingers crossed, still is) we are sure to find it soon enough!
And be sure to check out this video of this latest discovery by Curiosity, courtesy of NASA’s Jet Propulsion Laboratory:
Scientists from the OU have discovered a new phenomenon that could explain the long-debated mystery of how recent land features on Mars are formed in the absence of significant amounts of water. Credit: OUNews
Mars modern landscape is something of a paradox. It’s many surface features are very similar to those on Earth that are caused by water-borne erosion. But for the life of them, scientists cannot imagine how water could have flown on Mars’ cold and desiccated surface for most of Mars’ history. Whereas Mars was once a warmer, wetter place, it has had a very thin atmosphere for billions of years now, which makes water flow and erosion highly unlikely.
In fact, while the surface of Mars periodically becomes warm enough to allow for ice to thaw, liquid water would boil once exposed to the thin atmosphere. However, in a new study led by an international team of researchers from the UK, France and Switzerland, it has been determined that a different kind of transport process involving the sublimation of water ice could have led to the Martian landscape becoming what it is today.
The study, which was led Dr. Jan Raack – a Marie Sklodowska-Curie Research Fellow at The Open University – was recently published in the scientific journal Nature Communications. Titled “Water Induced Sediment Levitation Enhances Downslope Transport on Mars”, this research study consisted of experiments that tested how processes on Mars’ surface could allow water transport without it being in liquid form.
Reull Vallis, the river-like structure captured by the ESA’s Mars Express probe, is believed to have formed when running water flowed in the distant martian past. Credit and copyright: ESA/DLR/FU Berlin (G. Neukum)
To conduct their experiments, the team used the Mars Simulation Chamber, an instrument at The Open University that is capable of simulating the atmospheric conditions on Mars. This involved lowering the atmospheric pressure inside the chamber to what is normal for Mars – about 7 mbar, compared to 1000 mbar (1 bar or 100 kilopascals) here on Earth – while also adjusting temperatures.
On Mars, temperatures range from a low of -143 °C (-255 °F) during winter at the poles to a high of 35 °C (95 °F) at the equator during midday in the summer. Having recreated these conditions, the team found that when water ice exposed to the simulated Martian atmosphere, it would not simply melt. Instead, it would become unstable and begin violently boiling off.
However, the team also found that this process would be capable of moving large amounts of sand and sediment, which would effectively “levitate” on the boiling water. This means that, compared to Earth, relatively small amounts of liquid water are capable of moving sediment across the surface of Mars. These levitating pockets of sand and debris would be capable of forming tje large dunes, gullies, recurring slope lineae, and other features observed on Mars.
In the past, scientists have indicated how these features were the result of sediment transportation down slopes, but were unclear as to the mechanisms behind them. As Dr. Jan Raack explained in a OUNews press release:
“Our research has discovered that this levitation effect caused by boiling water under low pressure enables the rapid transport of sand and sediment across the surface. This is a new geological phenomenon, which doesn’t happen on Earth, and could be vital to understanding similar processes on other planetary surfaces.”
Illustration of the ESA Exomars 2020 Rover, which will explore the Red Planet in search for signs of ancient life. Credit:ESA
Through these experiments, Dr. Raack and his colleagues were able to shed light on how conditions on Mars could allow for features that we tend to associate with flowing water here on Earth. In addition to helping to resolve a somewhat contentious debate concerning Mars’ geological history and evolution, this study is also significant when it comes to future exploration missions.
Dr. Raack acknowledges the need for more research to confirm their study’s conclusions, and indicated that the ESA’s ExoMars 2020 Rover will be well-situated to conduct it once it is deployed :
“This is a controlled laboratory experiment, however, the research shows that the effects of relatively small amounts of water on Mars in forming features on the surface may have been widely underestimated. We need to carry out more research into how water levitates on Mars, and missions such as the ESA ExoMars 2020 Rover will provide vital insight to help us better understand our closest neighbour.”
Mosaic image of the Curiosity rover on Mars, which recently turned up more evidence that supports the idea that the planet was once habitability. Credit: NASA/JPL-Caltech/MSSS.
It has become a well-known scientific fact that billions of years ago, Mars once had a thicker atmosphere and liquid water on its surface. Scientists have also discovered that it was the gradual loss of this atmosphere, between 4.2 and 3.7 billion years ago, that caused Mars to go from being a warmer, wetter environment to the dry, freezing environment it is today.
Despite the existence of both a thicker atmosphere and water, questions remain as to whether or not Mars was truly habitable in the past. According to a new study from a team of researchers from the Los Alamos National Laboratory (LANL), the discovery of a specific mineral (boron) has added weight to the argument that Mars was once a potentially life-bearing world.
The study, titled “In situ detection of boron by ChemCam on Mars“, was recently published in the scientific journal Geophysical Research Letters. For the sake of this study, the LANL research team consulted data collected by the Chemistry and Camera (ChemCam) instrument aboard the Curiosity rover, which showed evidence of boron on the surface of Mars.
Mars, as it may have looked 4.2 billion years ago (left) and today (right). Credit: Kevin Gill
Boron, an element which is created by cosmic rays and is relatively rare in the Solar System, is necessary for the creation of ribonucleic acid – which is present in all forms of modern life. Essentially, RNA requires a key ingredient to form, which is a sugar called ribose. Like all sugars, ribose is highly unstable and decomposes quickly in water. As such, it needs another element to stabilize it, which is where boron comes into play.
As Patrick Gasda, a postdoctoral researcher at the Los Alamos National Laboratory and lead author on the paper, explained in a LANL press statement:
“Because borates may play an important role in making RNA – one of the building blocks of life – finding boron on Mars further opens the possibility that life could have once arisen on the planet. Borates are one possible bridge from simple organic molecules to RNA. Without RNA, you have no life. The presence of boron tells us that, if organics were present on Mars, these chemical reactions could have occurred.”
When boron is dissolved in water (which, as noted, Mars once had in abundance) it becomes borate. This compound (when combined with ribose) would act as a stabilizing agent, keeping the sugar together long enough so that RNA can form. As Gasda explained, “We detected borates in a crater on Mars that’s 3.8 billion years old, younger than the likely formation of life on Earth.”
Artist rendition of how the “lake” at Gale Crater on Mars may have looked millions of years ago. Credit and copyright: Kevin Gill.
The boron was detected by Curiosity’s laser-shooting ChemCam instrument, which was developed by the LANL in conjunction with France’s space agency, the National Center of Space Studies (CNES). It detected the element in veins of calcium sulfate minerals located in the Gale Crater, which means that boron was present in Mars’ groundwater and was preserved with other minerals when the water dissolved, leaving behind rich mineral veins.
This provides further evidence that the lake that is now known to have once filled the Gale Crater could have had life in it. During the time period in question, this lake would have experienced temperatures ranging from from 0 to 60 ° C (32 to 140 °F) and had a pH level that would have been neutral-to-alkaline. It also means that on ancient Mars, the conditions necessary for life would have existed, and independent of Earth to boot.
This is just one of many findings Curiosity has made related to the composition of Martian rocks. Since it touched down in the Gale Crater in 2012, the rover has been gathering chemical evidence of the ancient lake that once existed there, as well as geological evidence that has been preserved by sedimentary deposits. As the rover began to scale the slope of Mount Sharp, the composition of the surface began to change.
Whereas samples taken from the crater floor tended to contain more in the way of clays, samples collected higher up Mount Sharp contained more boron. These and other chemical traces are indications of how conditions under which sediments were deposited changed over time. Analysis conducted of the mountain’s layers has also showed how the movement of groundwater through these layers of sediment altered and transported elements (like boron).
MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity. Credits: NASA/JPL, illustration, T.Reyes
All of this is providing a picture of how Mars’ environment changed over the course of billions of years and affected the planet’s potential favorability for microbial life. And while scientists have a general picture of how Mars underwent a very significant transition billions of years ago, whether or not Martian life ever existed remains unknown.
The main goal of the Curiosity mission was to determine whether the area ever offered a habitable environment. Thanks to evidence of past water and the discovery of minerals like boron, this has been confirmed. In the coming years, the deployment of the Mars 2020 rover is expected to follow-up on these findings and shed more light on Mars’ case for past habitability.
Once it reaches the surface, the Mars 2020 rover – which relies on much of the same technology as Curiosity – will use an instrument called the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC). Also developed by the LANL, this “SuperCam” instrument will use spectrometers, a laser and a camera to search for organics and minerals that could indicate the existence of past microbial life.
If there is still preserved evidence of life to be found on Mars or – fingers crossed! – microbial life still exists there today, we can expect to find it before long. If that should be the case, human beings will finally know with certainty that life evolved on a planet other than Earth, and perhaps independent of it!
Bedrock at this site added to a puzzle about ancient Mars by indicating that a lake was present, but that little carbon dioxide was in the air to help keep a lake unfrozen. Credit: NASA/JPL-Caltech/MSSS
The study of Mars’ surface and atmosphere has unlocked some ancient secrets. Thanks to the efforts of the Curiosity rover and other missions, scientists are now aware of the fact that water once flowed on Mars and that the planet had a denser atmosphere. They have also been able to deduce what mechanics led to this atmosphere being depleted, which turned it into the cold, desiccated environment we see there today.
At the same time though, it has led to a rather intriguing paradox. Essentially, Mars is believed to have had warm, flowing water on its surface at a time when the Sun was one-third as warm as it is today. This would require that the Martian atmosphere had ample carbon dioxide in order to keep its surface warm enough. But based on the Curiosity rover’s latest findings, this doesn’t appear to be the case.
These findings were part of an analysis of data taken by the Curiosity’s Chemistry and Mineralogy X-ray Diffraction (CheMin) instrument, which has been used to study the mineral content of drill samples in the Gale Crater. The results of this analysis were recently published in Proceedings of the National Academy of Science, where the research team indicated that no traces of carbonates were found in any samples taken from the ancient lake bed.
Simulated view of Gale Crater Lake on Mars, depicting a lake of water partially filling Mars’ Gale Crater. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS
To break it down, evidence collected by Curiosity (and a slew of other rovers, landers and orbiters) has led scientists to conclude that roughly 3.5 billion years ago, Mars surface had lakes and flowing rivers. They have also determined, thanks to the many samples taken by Curiosity since it landed in the Gale Crater in 2011, that this geological feature was once a lake bed that gradually became filled with sedimentary deposits.
However, for Mars to have been warm enough for liquid water to exist, its atmosphere would have had to contain a certain amount of carbon dioxide – providing a sufficient Greenhouse Effect to compensate for the Sun’s diminished warmth. Since rock samples in the Gale Crater act as a geological record for what conditions were like billions of years ago, they would surely contain plenty of carbonate minerals if this were the case.
Carbonates are minerals that result from carbon dioxide combining with positively charged ions (like magnesium and iron) in water. Since these ions have been found to be in good supply in samples of Martian rock, and subsequent analysis has shown that conditions never became acidic to the point that the carbonates would have dissolved, there is no apparent reason why they wouldn’t be showing up.
Along with his team, Thomas Bristow – the principal investigator for the CheMin instrument on Curiosity – calculated what the minimum amount of atmospheric carbon dioxide would need to be, and how this would have been indicated by the levels of carbonate found in Martian rocks today. They then sorted through the years worth of the CheMin instrument’s data to see if there were any indications of these minerals.
Comparison of X-ray diffraction patterns of two different samples analyzed by Curiosity’s Chemistry and Mineralogy (CheMin) instrument. Credit: NASA/JPL-Caltech/Ames
But as he explained in a recent NASA press release, the findings simply didn’t measure up:
“We’ve been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined. It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us.”
In the end, Bristow and his team could not find even trace amounts of carbonates in the rock samples they analyzed. Even if just a few tens of millibars of carbon dioxide had been present in the atmosphere when a lake existed in the Gale Crater, it would have produced enough carbonates for Curiosity’s CheMin to detect. This latest find adds to a paradox that has been plaguing Mars researchers for years.
Basically, researchers have noted that there is a serious discrepancy between what surface features indicate about Mars’ past, and what chemical and geological evidence has to say. Not only is there plenty of evidence that the planet had a denser atmosphere in the past, more than four decades of orbital imaging (and years worth of surface data) have yielded ample geomorphological evidence that Mars once had surface water and an active hydrological cycle.
The Gale Crater – the landing location and trek of the Rover Curiosity – as it is today, imaged by the MRO. Credits: NASA/JPL, illustration, T.Reyes
However, scientists are still struggling to produce models that show how the Martian climate could have maintained the types of conditions necessary for this to have been the case. The only successful model so far has been one in which the atmosphere contained a significant amount of CO2 and hydrogen. Unfortunately, an explanation for how this atmosphere could be created and sustained remains elusive.
In addition, the geological and chemical evidence for such a atmosphere existing billions of years ago has also been in short supply. In the past, surveys by orbiters were unable to find evidence of carbonate minerals on the surface of Mars. It was hoped that surface missions, like Curiosity, would be able to resolve this by taking soil and drill samples where water had been known to exist.
But as Bristow explained, his team’s study has effectively closed the door on this:
“It’s been a mystery why there hasn’t been much carbonate seen from orbit. You could get out of the quandary by saying the carbonates may still be there, but we just can’t see them from orbit because they’re covered by dust, or buried, or we’re not looking in the right place. The Curiosity results bring the paradox to a focus. This is the first time we’ve checked for carbonates on the ground in a rock we know formed from sediments deposited under water.”
Annontated version of the bedrock site in the Gale Crater where the Curiosity rover has taken drill samples. Credit: NASA/JPL-Caltech/MSSS
There are several possible explanations for this paradox. On the one hand, some scientists have argued that the Gale Crater Lake may not have been an open body of water and was perhaps covered in ice, which was just thin enough to still allow for sediments to get in. The problem with this explanation is that if this were true, there would be discernible indications left behind – which would include deep cracks in the soft sedimentary lakebed rock.
But since these indications have not been found, scientists are left with two lines of evidence that do not match up. As Ashwin Vasavada, Curiosity’s Project Scientist, put it:
“Curiosity’s traverse through streambeds, deltas, and hundreds of vertical feet of mud deposited in ancient lakes calls out for a vigorous hydrological system supplying the water and sediment to create the rocks we’re finding. Carbon dioxide, mixed with other gases like hydrogen, has been the leading candidate for the warming influence needed for such a system. This surprising result would seem to take it out of the running.”
Luckily, incongruities in science are what allow for new and better theories to be developed. And as the exploration of the Martian surface continues – which will benefit from the arrival of the ExoMars and the Mars 2020missions in the coming years – we can expect additional evidence to emerge. Hopefully, it will help point the way towards a resolution for this paradox, and not complicate our theories even more!
Cirrus clouds in the Martian atmosphere may have helped keep Mars warm enough for liquid water to sculpt the Martian surface. Image: Mars Exploration Rover Mission, Cornell, JPL, NASA
Many features on the surface of Mars hint at the presence of liquid water in the past. These range from the Valles Marineris, a 4,000 km long and 7 km deep system of canyons, to the tiny hematite spherules called “blueberries“. These features suggest that liquid water played a vital role in shaping Mars.
Some studies show that these features have volcanic origins, but a new study from two researchers at the Carl Sagan Institute and the NASA Virtual Planet Laboratory put the focus back on liquid water. The model that the two came up with says that, if other conditions were met, cirrus clouds could have provided the necessary insulation for liquid water to flow. The two researchers, Ramses M. Ramirez and James F. Kasting, constructed a climate model to test their idea.
Cirrus clouds are thin, wispy clouds that appear regularly on Earth. They’ve also been seen on Jupiter, Saturn, Uranus, possibly Neptune, and on Mars. Cirrus clouds themselves don’t produce rain. Whatever precipitation they produce, in the form of ice crystals, evaporates before reaching the surface. The researchers behind this study focussed on cirrus clouds’ because they tend to warm the air underneath them by 10 degrees Celsius.
Cirrus clouds over Poznan, Poland. Image: Radomil, http://creativecommons.org/licenses/by-sa/3.0/
If enough of Mars was covered by cirrus clouds, then the surface would be warm enough for liquid water to flow. On Earth, cirrus clouds cover up to 25% of the Earth and have a measurable heating effect. They allow sunlight in, but absorb outgoing infrared radiation. Kasting and Ramirez sought to show how the same thing might happen on Mars, and how much cirrus cloud cover would be necessary.
The cirrus clouds themselves wouldn’t have created all the warmth. Impacts from comets and asteroids would have created the heat, and extensive cirrus cloud cover would have trapped that heat in the Martian atmosphere.
The two researchers conducted a model, called a single-column radiative-convective climate model. They then tested different ice crystal sizes, the portion of the sky covered by cirrus clouds, and the thicknesses of those clouds, to simulate different conditions on Mars.
A color mosaic of Candor Chasma (part of Mars’ Valles Marineris) based on data from Voyager 1 and Voyager 2. Credit: NASA
They found that under the right circumstances, the clouds in the early Martian atmosphere could last 4 to 5 times longer than on Earth. This favors the idea that cirrus clouds could have kept Mars warm enough for liquid water. However, they also found that 75% to 100% of the planet would have to be covered by cirrus. That amount of cloud cover seems unlikely according to the researchers, and they suggest that 50% would be more realistic. This figure is similar to Earth’s cloud cover, including all cloud types, not just cirrus.
As they adjusted the parameters of their model, they found that thicker clouds and smaller particle sizes reduced the heating effect of the cirrus cloud cover. This left a very thin set of parameters in which cirrus clouds could have kept Mars warm enough for liquid water. But their modelling also showed that there is one way that cirrus clouds could have done the job.
If the ancient Martian surface temperature was lower than 273 Kelvin, the value used in the model, then it would be possible for cirrus clouds to do their thing. And it would only have to be lower by 8 degrees Kelvin for that to happen. At times in Earth’s past, the surface temperature has been lower by 7 degrees Kelvin. The question is, might Mars have had a similarly lower temperature?
So, where does that leave us? We don’t have a definitive answer yet. It’s possible that cirrus clouds on Mars could have helped to keep the planet warm enough for liquid water. The modelling done by Ramirez and Kasting shows us what parameters were required for that to happen.
These dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars are inferred to have been formed by contemporary flowing water. However, a new study by planetary scientists indicates that these may actually be the result of dry flows. Credits: NASA/JPL/University of Arizona
These dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars are inferred to have been formed by contemporary flowing water. Recently, planetary scientists detected hydrated salts on these slopes at Hale crater, corroborating their original hypothesis that the streaks are indeed formed by liquid water. The blue color seen upslope of the dark streaks are thought not to be related to their formation, but instead are from the presence of the mineral pyroxene.
The image is produced by draping an orthorectified Infrared-Red-Blue/Green(IRB)) false color image on a Digital Terrain Model (DTM). This model was produced by researchers at the University of Arizona, much like the High Resolution Imaging Science Experiment (University of Arizona). The vertical exaggeration is 1.5.
NASA and Mars planetary scientists announced today (Sept. 28) that salty “liquid water flows intermittently” across multiple spots on the surface of today’s Mars – trumpeting a major scientific discovery with far reaching implications regarding the search for life beyond Earth and bolstering the chances for the possible existence of present day Martian microbes.
Utilizing spectroscopic measurements and imaging gathered by NASA’s Mars Reconnaissance Orbiter (MRO), researchers found the first strong evidence confirming that briny water flows on the Red Planet today along dark streaks moving downhill on crater slopes and mountain sides, during warmer seasons.
“Mars is not the dry, arid planet that we thought of in the past. Today we announce that under certain circumstances, liquid water has been found on Mars,” said Jim Green, NASA Planetary Science Director at NASA Headquarters, at a media briefing held today, Sept 28.
“When you look at Earth, water is an essential ingredient. Everywhere we go where there’s liquid water, whether its deep in the Earth or in the arid regions, we find life. This is tremendously exciting.”
“We haven’t been able to answer the question – does life exist beyond Earth? But following the water is a critical element of that. We now have great opportunities to be in the right locations on Mars to thoroughly investigate that,” Green elaborated.
“Water! Strong evidence that liquid water flows on present-day Mars,” NASA officials tweeted about the discovery.
The evidence comes in the form of the detection of mysterious dark streaks, as long as 100 meters, showing signatures of hydrated salt minerals periodically flowing in liquid water down steep slopes on the Red Planet that “appear to ebb and flow over time.”
The source of the water is likely from the shallow subsurface or possibly absorbed from the atmosphere.
Dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesized to be formed by flow of briny liquid water on Mars. The image is produced by draping an orthorectified (RED) image (ESP_031059_1685) on a Digital Terrain Model (DTM) of the same site produced by High Resolution Imaging Science Experiment (University of Arizona). Vertical exaggeration is 1.5. Credits: NASA/JPL/University of Arizona
Water is a key prerequisite for the formation and evolution of life as we know it. So the new finding significantly bolsters the chances that present day extant life could exist on the Red Planet.
“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.”
“This increases the chance that life could exist on Mars today,” noted Grunsfeld.
The data were gathered by and the conclusions are based on using two scientific instruments – the high resolution imaging spectrometer on MRO known as High Resolution Imaging Science Experiment (HiRISE), as well as MRO’s mineral mapping Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
The mysterious dark streaks of downhill flows are known as recurring slope lineae (RSL).
They were first detected in 2010 at dozens of sites on the sun facing slopes of deep craters by Lujendra Ojha, then a University of Arizona undergraduate student.
The new finding is highly significant because until today’s announcement, there was no strong evidence that liquid water could actually exist on the Martian surface because the atmospheric pressure was thought to be far too low – its less than one percent of Earth’s.
The flow of water is occasional and not permanent, seasonally variable and dependent on having just the right mix of atmospheric, temperature and surface conditions with salt deposits on Mars.
Portions of Mars were covered with an ocean of water billions of years ago when the planet was far warmer and more hospitable to life. But it underwent a dramatic climate change some 3 billion years ago and lost most of that water.
The RSL with flowing water appear in at least three different locations on Mars – including Hale crater, Horowitz crater and Palikir crater – when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius). They appear during warm seasons, fade in cooler seasons and disappear during colder times.
Pure surface water ice would simply sublimate and evaporate away as the temperature rises. Mixing in surface salts lowers the melting point of ice, thereby allowing the water to potentially liquefy on Mars surface for a certain period of time rather than sublimating rapidly away.
“These are dark streaks that form in late spring, grow through the summer and then disappear in the fall,” said Michael Meyer lead scientist for the Mars Exploration Program at NASA Headquarters, at the media briefing.
Years of painstaking effort and laboratory work was required to verify and corroborate the finding of flowing liquid water.
“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 Meyer. “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.”
The dark, narrow streaks flowing downhill on Mars at sites such as this portion of Horowitz Crater are inferred to be formed by seasonal flow of water on modern-day Mars. The streaks are roughly the length of a football field. These dark features on the slopes are called “recurring slope lineae” or RSL. The imaging and topographical information in this processed view come from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/Univ. of Arizona
Along with the media announcement, the researchers published their findings today in a refereed scientific paper in the Sept. 28 issue of Nature Geoscience.
“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, now at the Georgia Institute of Technology (Georgia Tech) in Atlanta, and lead author of the Sept. 28 publication in Nature Geoscience.
The scientists “interpret the spectral signatures as caused by hydrated minerals called perchlorates.”
Ojha said the chemical signatures from CRISM were most consistent with the detection of mixtures of magnesium perchlorate, magnesium chlorate and sodium perchlorate, based on lab experiments.
“Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius).”
Perchlorates have previously been detected in Martian soil by two of NASA’s surface missions – the Phoenix lander and the Curiosity rover. There is also some evidence that NASA’s Viking missions in the 1970s measured signatures of these salts.
On Earth concentration of perchlorates are found in deserts.
This also marks the first time perchlorates have been identified from Mars orbit.
So NASA astronaut Mark Kelly exclaimed that he was also super excited about the findings, from his perch serving as Commander aboard the International Space Station (ISS), where he is a member of the first ever “1 Year ISS Mission Crew” aimed at learning how the human body will adapt to the long term missions required to send astronauts to Mars and back.
“One reason why NASA’s discovery of liquid water on #Mars is so exciting: we know anywhere there’s water on Earth, there’s some form of life,” Kelly tweeted today from on board the ISS, upon hearing today’s news.
The discovery of liquid water on Mars could also be a boon to future astronauts who could use it as a natural resource to ‘live off the land’ for sustenance and to make rocket fuel.
“If going to Mars on my Year In Space, I’d arrive soon to find water! H20 > rocket fuel, which means I could find my way back home too!,” Kelly wrote on his Facebook page.
“When most people talk about water on Mars, they’re usually talking about ancient water or frozen water,” Ojha explained.
“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.”
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
