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    Study: Rocks from Mars’ Jezero Crater, which likely predate life on Earth, contain signs of water

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    In a new study appearing today in the journal AGU Advances, scientists at MIT and NASA report that seven rock samples collected along the “fan front” of Mars’ Jezero Crater contain minerals that are typically formed in water. The findings suggest that the rocks were originally deposited by water, or may have formed in the presence of water.The seven samples were collected by NASA’s Perseverance rover in 2022 during its exploration of the crater’s western slope, where some rocks were hypothesized to have formed in what is now a dried-up ancient lake. Members of the Perseverance science team, including MIT scientists, have studied the rover’s images and chemical analyses of the samples, and confirmed that the rocks indeed contain signs of water, and that the crater was likely once a watery, habitable environment.Whether the crater was actually inhabited is yet unknown. The team found that the presence of organic matter — the starting material for life — cannot be confirmed, at least based on the rover’s measurements. But judging from the rocks’ mineral content, scientists believe the samples are their best chance of finding signs of ancient Martian life once the rocks are returned to Earth for more detailed analysis.“These rocks confirm the presence, at least temporarily, of habitable environments on Mars,” says the study’s lead author, Tanja Bosak, professor of geobiology in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “What we’ve found is that indeed there was a lot of water activity. For how long, we don’t know, but certainly for long enough to create these big sedimentary deposits.”What’s more, some of the collected samples may have originally been deposited in the ancient lake more than 3.5 billion years ago — before even the first signs of life on Earth.“These are the oldest rocks that may have been deposited by water, that we’ve ever laid hands or rover arms on,” says co-author Benjamin Weiss, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. “That’s exciting, because it means these are the most promising rocks that may have preserved fossils, and signatures of life.”The study’s MIT co-authors include postdoc Eva Scheller, and research scientist Elias Mansbach, along with members of the Perseverance science team.At the front

    NASA’s Perseverance rover collected rock samples from two locations seen in this image of Mars’ Jezero Crater: “Wildcat Ridge” (lower left) and “Skinner Ridge” (upper right).

    Credit: NASA/JPL-Caltech/ASU/MSSS

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    The new rock samples were collected in 2022 as part of the rover’s Fan Front Campaign — an exploratory phase during which Perseverance traversed Jezero Crater’s western slope, where a fan-like region contains sedimentary, layered rocks. Scientists suspect that this “fan front” is an ancient delta that was created by sediment that flowed with a river and settled into a now bone-dry lakebed. If life existed on Mars, scientists believe that it could be preserved in the layers of sediment along the fan front.In the end, Perseverance collected seven samples from various locations along the fan front. The rover obtained each sample by drilling into the Martian bedrock and extracting a pencil-sized core, which it then sealed in a tube to one day be retrieved and returned to Earth for detailed analysis.

    Composed of multiple images from NASA’s Perseverance Mars rover, this mosaic shows a rocky outcrop called “Wildcat Ridge,” where the rover extracted two rock cores and abraded a circular patch to investigate the rock’s composition.

    Credit: NASA/JPL-Caltech/ASU/MSSS

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    Prior to extracting the cores, the rover took images of the surrounding sediments at each of the seven locations. The science team then processed the imaging data to estimate a sediment’s average grain size and mineral composition. This analysis showed that all seven collected samples likely contain signs of water, suggesting that they were initially deposited by water.Specifically, Bosak and her colleagues found evidence of certain minerals in the sediments that are known to precipitate out of water.“We found lots of minerals like carbonates, which are what make reefs on Earth,” Bosak says. “And it’s really an ideal material that can preserve fossils of microbial life.”Interestingly, the researchers also identified sulfates in some samples that were collected at the base of the fan front. Sulfates are minerals that form in very salty water — another sign that water was present in the crater at one time — though very salty water, Bosak notes, “is not necessarily the best thing for life.” If the entire crater was once filled with very salty water, then it would be difficult for any form of life to thrive. But if only the bottom of the lake were briny, that could be an advantage, at least for preserving any signs of life that may have lived further up, in less salty layers, that eventually died and drifted down to the bottom.“However salty it was, if there were any organics present, it’s like pickling something in salt,” Bosak says. “If there was life that fell into the salty layer, it would be very well-preserved.”Fuzzy fingerprintsBut the team emphasizes that organic matter has not been confidently detected by the rover’s instruments. Organic matter can be signs of life, but can also be produced by certain geological processes that have nothing to do with living matter. Perseverance’s predecessor, the Curiosity rover, had detected organic matter throughout Mars’ Gale Crater, which scientists suspect may have come from asteroids that made impact with Mars in the past.And in a previous campaign, Perseverance detected what appeared to be organic molecules at multiple locations along Jezero Crater’s floor. These observations were taken by the rover’s Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument, which uses ultraviolet light to scan the Martian surface. If organics are present, they can glow, similar to material under a blacklight. The wavelengths at which the material glows act as a sort of fingerprint for the kind of organic molecules that are present.In Perseverance’s previous exploration of the crater floor, SHERLOC appeared to pick up signs of organic molecules throughout the region, and later, at some locations along the fan front. But a careful analysis, led by MIT’s Eva Scheller, has found that while the particular wavelengths observed could be signs of organic matter, they could just as well be signatures of substances that have nothing to do with organic matter.“It turns out that cerium metals incorporated in minerals actually produce very similar signals as the organic matter,” Scheller says. “When investigated, the potential organic signals were strongly correlated with phosphate minerals, which always contain some cerium.”Scheller’s work shows that the rover’s measurements cannot be interpreted definitively as organic matter.“This is not bad news,” Bosak says. “It just tells us there is not very abundant organic matter. It’s still possible that it’s there. It’s just below the rover’s detection limit.”When the collected samples are finally sent back to Earth, Bosak says laboratory instruments will have more than enough sensitivity to detect any organic matter that might lie within.“On Earth, once we have microscopes with nanometer-scale resolution, and various types of instruments that we cannot staff on one rover, then we can actually attempt to look for life,” she says.This work was supported, in part, by NASA. More

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      in Environment

      Studying rivers from worlds away

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      Rivers have flowed on two other worlds in the solar system besides Earth: Mars, where dry tracks and craters are all that’s left of ancient rivers and lakes, and Titan, Saturn’s largest moon, where rivers of liquid methane still flow today.

      A new technique developed by MIT geologists allows scientists to see how intensely rivers used to flow on Mars, and how they currently flow on Titan. The method uses satellite observations to estimate the rate at which rivers move fluid and sediment downstream.

      Applying their new technique, the MIT team calculated how fast and deep rivers were in certain regions on Mars more than 1 billion years ago. They also made similar estimates for currently active rivers on Titan, even though the moon’s thick atmosphere and distance from Earth make it harder to explore, with far fewer available images of its surface than those of Mars.

      “What’s exciting about Titan is that it’s active. With this technique, we have a method to make real predictions for a place where we won’t get more data for a long time,” says Taylor Perron, the Cecil and Ida Green Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “And on Mars, it gives us a time machine, to take the rivers that are dead now and get a sense of what they were like when they were actively flowing.”

      Perron and his colleagues have published their results today in the Proceedings of the National Academy of Sciences. Perron’s MIT co-authors are first author Samuel Birch, Paul Corlies, and Jason Soderblom, with Rose Palermo and Andrew Ashton of the Woods Hole Oceanographic Institution (WHOI), Gary Parker of the University of Illinois at Urbana-Champaign, and collaborators from the University of California at Los Angeles, Yale University, and Cornell University.

      River math

      The team’s study grew out of Perron and Birch’s puzzlement over Titan’s rivers. The images taken by NASA’s Cassini spacecraft have shown a curious lack of fan-shaped deltas at the mouths of most of the moon’s rivers, contrary to many rivers on Earth. Could it be that Titan’s rivers don’t carry enough flow or sediment to build deltas?

      The group built on the work of co-author Gary Parker, who in the 2000s developed a series of mathematical equations to describe river flow on Earth. Parker had studied measurements of rivers taken directly in the field by others. From these data, he found there were certain universal relationships between a river’s physical dimensions — its width, depth, and slope — and the rate at which it flowed. He drew up equations to describe these relationships mathematically, accounting for other variables such as the gravitational field acting on the river, and the size and density of the sediment being pushed along a river’s bed.

      “This means that rivers with different gravity and materials should follow similar relationships,” Perron says. “That opened up a possibility to apply this to other planets too.”

      Getting a glimpse

      On Earth, geologists can make field measurements of a river’s width, slope, and average sediment size, all of which can be fed into Parker’s equations to accurately predict a river’s flow rate, or how much water and sediment it can move downstream. But for rivers on other planets, measurements are more limited, and largely based on images and elevation measurements collected by remote satellites. For Mars, multiple orbiters have taken high-resolution images of the planet. For Titan, views are few and far between.

      Birch realized that any estimate of river flow on Mars or Titan would have to be based on the few characteristics that can be measured from remote images and topography — namely, a river’s width and slope. With some algebraic tinkering, he adapted Parker’s equations to work only with width and slope inputs. He then assembled data from 491 rivers on Earth, tested the modified equations on these rivers, and found that the predictions based solely on each river’s width and slope were accurate.

      Then, he applied the equations to Mars, and specifically, to the ancient rivers leading into Gale and Jezero Craters, both of which are thought to have been water-filled lakes billions of years ago. To predict the flow rate of each river, he plugged into the equations Mars’ gravity, and estimates of each river’s width and slope, based on images and elevation measurements taken by orbiting satellites.

      From their predictions of flow rate, the team found that rivers likely flowed for at least 100,000 years at Gale Crater and at least 1 million years at Jezero Crater — long enough to have possibly supported life. They were also able to compare their predictions of the average size of sediment on each river’s bed with actual field measurements of Martian grains near each river, taken by NASA’s Curiosity and Perseverance rovers. These few field measurements allowed the team to check that their equations, applied on Mars, were accurate.

      The team then took their approach to Titan. They zeroed in on two locations where river slopes can be measured, including a river that flows into a lake the size of Lake Ontario. This river appears to form a delta as it feeds into the lake. However, the delta is one of only a few thought to exist on the moon — nearly every viewable river flowing into a lake mysteriously lacks a delta. The team also applied their method to one of these other delta-less rivers.

      They calculated both rivers’ flow and found that they may be comparable to some of the biggest rivers on Earth, with deltas estimated to have a flow rate as large as the Mississippi. Both rivers should move enough sediment to build up deltas. Yet, most rivers on Titan lack the fan-shaped deposits. Something else must be at work to explain this lack of river deposits.

      In another finding, the team calculated that rivers on Titan should be wider and have a gentler slope than rivers carrying the same flow on Earth or Mars. “Titan is the most Earth-like place,” Birch says. ”We’ve only gotten a glimpse of it. There’s so much more that we know is down there, and this remote technique is pushing us a little closer.”

      This research was supported, in part, by NASA and the Heising-Simons Foundation. More

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      in Energy

      Understanding boiling to help the nuclear industry and space missions

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      To launch extended missions in space, the National Aeronautics and Space Administration (NASA) is borrowing a page from the nuclear engineering industry: It is trying to understand how boiling works.

      Planning for long-term missions has NASA researching ways of packing the least amount of cryogenic fuel possible for efficient liftoff. One potential solution is to refuel the rocket in space using fuel depots placed in low Earth orbits. This way, the spacecraft can carry the lightest fuel load — enough to reach the low Earth orbit to refuel as necessary and complete the mission. But refueling in space requires a thorough knowledge of cryogenic fuels.

      “We [need to understand] how boiling of cryogens behaves in microgravity conditions [encountered in space],” says Florian Chavagnat, a sixth-year doctoral candidate in the Department of Nuclear Science and Engineering (NSE). After all, understanding how cryogens boil in space is critical to NASA’s fuel management strategy. The vast majority of studies on boiling evaluate fluids that boil at high temperatures, which doesn’t necessarily apply to cryogens. Under the advisement of Matteo Bucci and Emilio Baglietto, Chavagnat is working on NASA-sponsored research about cryogens and the way the lack of buoyancy in space affects boiling.

      A childhood spent tinkering

      A deep understanding of engineering and physical phenomena is exactly what Chavagnat developed growing up in Boussy-Saint-Antoine, a suburb of Paris, with parents who worked for SNCF, the national state-owned rail company. Chavagnat remembers discussing the working of trains and motors with his engineer dad and building a variety of balsa-wood models. One of his memorable projects was a sailboat propelled by a motor from an electric toothbrush.

      By the time he was a teenager, Chavagnat received a metal lathe as a gift. His tinkering became an obsession; a compressed air engine was a favorite project. Soon his parents’ small shed, meant for gardening, became a factory, Chavagnat recalls, laughing.

      A lifelong love of math and physics propelled a path to the National Institute of Applied Science in Rouen, Normandy, where Chavagnat studied energetics and propulsion as part of a five-year engineering program. In his final year, Chavagnat studied atomic engineering from INSTN Paris-Saclay, part of the esteemed French Alternative Energies and Atomic Energy Commission (CEA).

      The final year of studies at CEA required a six-month-long internship, which traditionally sets the course for a job. Chavagnat decided to take a chance and apply for an internship at MIT NSE instead, knowing his future course might be uncertain. “I didn’t take a lot of risk in my life, but this one was a big risk,” Chavagnat says. The gamble paid off: Chavagnat won the internship with Charles Forsberg, which paved the way for his admission as a doctoral student. “I selected MIT because it has always been my dream school,” Chavagnat says. He also enjoyed the idea of challenging himself to improve his English-speaking skills.

      A love of physics and heat transfer

      Chavagnat loves physics — “if I can study any problem in physics, I’d be happy” he says — which led him to working on heat transfer, more specifically on boiling heat transfer. His early doctoral research focused on transient boiling in nuclear reactors, part of which has been published in the International Journal of Heat and Mass Transfer.

      Chavagnat’s research targets a specific kind of nuclear reactor called a material test reactor (MTR). Nuclear scientists use MTRs to understand how materials used in plant operations might behave under long-term use. Densely packed nuclear fuel, running at high power, simulates long-term effects using a very intense neutron flux.

      To prevent failure, operators limit reactor temperature by flowing very cold water at high velocity. When reactor heat power increases uncontrollably, the piped water begins to boil. Boiling works to prevent meltdown by altering neutron moderation and extracting heat from the fuel. “[Unfortunately], that only works until you reach a certain heat flux at the fuel cladding, after which the efficiency completely drops,” Chavagnat says. Once the critical heat flux is reached, water vapor starts to blanket and insulate the fuel elements, leading to rapidly rising cladding temperatures and potential burnout.

      The key is to figure out the behavior of maximum boiling heat flux under routine MTR conditions — cold water, high flow velocity, and narrow spacing between the fuel elements.

      Study of cryogenic boiling

      Boiling continues to occupy center stage as Chavagnat pursues the question for NASA. Cryogens boil at very low temperatures, so the question of how to prevent fuel loss from routine space-based operations is an important one to answer.

      Chavagnat is studying how boiling would behave under reduced or absent buoyancy, which are the conditions cryogenic rocket fuel will encounter in space.

      To reproduce space-like conditions on Earth, buoyancy can be modified without going to space. Chavagnat is manipulating the inclination of the boiling surface — placing it upside down is an example — such that buoyancy does not do what it usually does: help bubbles break away from the surface. He is also performing boiling experiments in parabolic flights to simulate microgravity, similar to what is experienced aboard the International Space Station.

      Chavagnat designed and built equipment which can perform both methods with minimum changes. “We observed nitrogen boiling on our surface by imaging it using two high-speed video cameras,” he says. The experiment was approved to go on board the parabolic flights operated by Zero-G, a company that operates weightless flights. The team successfully completed four parabolic flights in 2022.

      “Flying an experiment aboard an aircraft and operating it in microgravity is an incredible experience, but is challenging,” Chavagnat says, “Knowing the details the experiment is a must, but other skills are quite useful — in particular, working as a team, being able to manage high stress levels, and being able to work while being motion-sick.” Another challenge is that the majority of issues cannot be fixed once aboard, as aircraft pilots perform the parabola (each lasting 17 seconds) almost back-to-back.

      Throughout his research at MIT, Chavagnat has been captivated by how complex a simple phenomenon like boiling can truly be. “In your childhood, you have a certain idea of how boiling looks, relatively slow bubbles that you can see with the naked eye,” he says, “but you don’t realize the complexity until you see it with your own eyes.”

      In his infrequent spare time, Chavagnat plays soccer with the NSE’s team, the Atom Smashers. The group meets only five times a semester so it’s a low-key commitment, says Chavagnat who spends most of his time at the lab. “I am doing mostly experiments at MIT; it turns out the skills I learned in my shed when I was 15 are actually quite useful here,” he laughs. More

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      in Security

      Rover images confirm Jezero crater is an ancient Martian lake

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      The first scientific analysis of images taken by NASA’s Perseverance rover has now confirmed that Mars’ Jezero crater — which today is a dry, wind-eroded depression — was once a quiet lake, fed steadily by a small river some 3.7 billion years ago.

      The images also reveal evidence that the crater endured flash floods. This flooding was energetic enough to sweep up large boulders from tens of miles upstream and deposit them into the lakebed, where the massive rocks lie today.

      The new analysis, published today in the journal Science, is based on images of the outcropping rocks inside the crater on its western side. Satellites had previously shown that this outcrop, seen from above, resembled river deltas on Earth, where layers of sediment are deposited in the shape of a fan as the river feeds into a lake.

      Perseverance’s new images, taken from inside the crater, confirm that this outcrop was indeed a river delta. Based on the sedimentary layers in the outcrop, it appears that the river delta fed into a lake that was calm for much of its existence, until a dramatic shift in climate triggered episodic flooding at or toward the end of the lake’s history.

      “If you look at these images, you’re basically staring at this epic desert landscape. It’s the most forlorn place you could ever visit,” says Benjamin Weiss, professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences and a member of the analysis team. “There’s not a drop of water anywhere, and yet, here we have evidence of a very different past. Something very profound happened in the planet’s history.”

      As the rover explores the crater, scientists hope to uncover more clues to its climatic evolution. Now that they have confirmed the crater was once a lake environment, they believe its sediments could hold traces of ancient aqueous life. In its mission going forward, Perseverance will look for locations to collect and preserve sediments. These samples will eventually be returned to Earth, where scientists can probe them for Martian biosignatures.

      “We now have the opportunity to look for fossils,” says team member Tanja Bosak, associate professor of geobiology at MIT. “It will take some time to get to the rocks that we really hope to sample for signs of life. So, it’s a marathon, with a lot of potential.”

      Tilted beds

      On Feb. 18, 2021, the Perseverance rover landed on the floor of Jezero crater, a little more than a mile away from its western fan-shaped outcrop. In the first three months, the vehicle remained stationary as NASA engineers performed remote checks of the rover’s many instruments.

      During this time, two of Perseverance’s cameras, Mastcam-Z and the SuperCam Remote Micro-Imager (RMI), captured images of their surroundings, including long-distance photos of the outcrop’s edge and a formation known as Kodiak butte, a smaller outcop that planetary geologists surmise may have once been connected to the main fan-shaped outcrop but has since partially eroded.

      Once the rover downlinked images to Earth, NASA’s Perseverance science team processed and combined the images, and were able to observe distinct beds of sediment along Kodiak butte in surprisingly high resolution. The researchers measured each layer’s thickness, slope, and lateral extent, finding that the sediment must have been deposited by flowing water into a lake, rather than by wind, sheet-like floods, or other geologic processes.

      The rover also captured similar tilted sediment beds along the main outcrop. These images, together with those of Kodiak, confirm that the fan-shaped formation was indeed an ancient delta and that this delta fed into an ancient Martian lake.

      “Without driving anywhere, the rover was able to solve one of the big unknowns, which was that this crater was once a lake,” Weiss says. “Until we actually landed there and confirmed it was a lake, it was always a question.”

      Boulder flow

      When the researchers took a closer look at images of the main outcrop, they noticed large boulders and cobbles embedded in the youngest, topmost layers of the delta. Some boulders measured as wide as 1 meter across, and were estimated to weigh up to several tons. These massive rocks, the team concluded, must have come from outside the crater, and was likely part of bedrock located on the crater rim or else 40 or more miles upstream.

      Judging from their current location and dimensions, the team says the boulders were carried downstream and into the lakebed by a flash-flood that flowed up to 9 meters per second and moved up to 3,000 cubic meters of water per second.

      “You need energetic flood conditions to carry rocks that big and heavy,” Weiss says. “It’s a special thing that may be indicative of a fundamental change in the local hydrology or perhaps the regional climate on Mars.”

      Because the huge rocks lie in the upper layers of the delta, they represent the most recently deposited material. The boulders sit atop layers of older, much finer sediment. This stratification, the researchers say, indicates that for much of its existence, the ancient lake was filled by a gently flowing river. Fine sediments — and possibly organic material — drifted down the river, and settled into a gradual, sloping delta.

      However, the crater later experienced sudden flash floods that deposited large boulders onto the delta. Once the lake dried up, and over billions of years wind eroded the landscape, leaving the crater we see today.

      The cause of this climate turnaround is unknown, although Weiss says the delta’s boulders may hold some answers.

      “The most surprising thing that’s come out of these images is the potential opportunity to catch the time when this crater transitioned from an Earth-like habitable environment, to this desolate landscape wasteland we see now,” he says. “These boulder beds may be records of this transition, and we haven’t seen this in other places on Mars.”

      This research was supported, in part, by NASA. More