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ExoMars orbiter continues hunt for key signs of life on Mars


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    • By NASA
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      The mystery of why life uses molecules with specific orientations has deepened with a NASA-funded discovery that RNA — a key molecule thought to have potentially held the instructions for life before DNA emerged — can favor making the building blocks of proteins in either the left-hand or the right-hand orientation. Resolving this mystery could provide clues to the origin of life. The findings appear in research recently published in Nature Communications.
      Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes (catalysts that speed up or regulate chemical reactions). Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acid building blocks in a huge variety of arrangements to make millions of different proteins. Some amino acid molecules can be built in two ways, such that mirror-image versions exist, like your hands, and life uses the left-handed variety of these amino acids. Although life based on right-handed amino acids would presumably work fine, the two mirror images are rarely mixed in biology, a characteristic of life called homochirality. It is a mystery to scientists why life chose the left-handed variety over the right-handed one.
      A diagram of left-handed and right-handed versions of the amino acid isovaline, found in the Murchison meteorite.NASA DNA (deoxyribonucleic acid) is the molecule that holds the instructions for building and running a living organism. However, DNA is complex and specialized; it “subcontracts” the work of reading the instructions to RNA (ribonucleic acid) molecules and building proteins to ribosome molecules. DNA’s specialization and complexity lead scientists to think that something simpler should have preceded it billions of years ago during the early evolution of life. A leading candidate for this is RNA, which can both store genetic information and build proteins. The hypothesis that RNA may have preceded DNA is called the “RNA world” hypothesis.
      If the RNA world proposition is correct, then perhaps something about RNA caused it to favor building left-handed proteins over right-handed ones. However, the new work did not support this idea, deepening the mystery of why life went with left-handed proteins.
      The experiment tested RNA molecules that act like enzymes to build proteins, called ribozymes. “The experiment demonstrated that ribozymes can favor either left- or right-handed amino acids, indicating that RNA worlds, in general, would not necessarily have a strong bias for the form of amino acids we observe in biology now,” said Irene Chen, of the University of California, Los Angeles (UCLA) Samueli School of Engineering, corresponding author of the Nature Communications paper.
      In the experiment, the researchers simulated what could have been early-Earth conditions of the RNA world. They incubated a solution containing ribozymes and amino acid precursors to see the relative percentages of the right-handed and left-handed amino acid, phenylalanine, that it would help produce. They tested 15 different ribozyme combinations and found that ribozymes can favor either left-handed or right-handed amino acids. This suggested that RNA did not initially have a predisposed chemical bias for one form of amino acids. This lack of preference challenges the notion that early life was predisposed to select left-handed-amino acids, which dominate in modern proteins.
      “The findings suggest that life’s eventual homochirality might not be a result of chemical determinism but could have emerged through later evolutionary pressures,” said co-author Alberto Vázquez-Salazar, a UCLA postdoctoral scholar and member of Chen’s research group.
      Earth’s prebiotic history lies beyond the oldest part of the fossil record, which has been erased by plate tectonics, the slow churning of Earth’s crust. During that time, the planet was likely bombarded by asteroids, which may have delivered some of life’s building blocks, such as amino acids. In parallel to chemical experiments, other origin-of-life researchers have been looking at molecular evidence from meteorites and asteroids.
      “Understanding the chemical properties of life helps us know what to look for in our search for life across the solar system,” said co-author Jason Dworkin, senior scientist for astrobiology at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and director of Goddard’s Astrobiology Analytical Laboratory.
      Dworkin is the project scientist on NASA’s OSIRIS-REx mission, which extracted samples from the asteroid Bennu and delivered them to Earth last year for further study.
      “We are analyzing OSIRIS-REx samples for the chirality (handedness) of individual amino acids, and in the future, samples from Mars will also be tested in laboratories for evidence of life including ribozymes and proteins,” said Dworkin.
      The research was supported by grants from NASA, the Simons Foundation Collaboration on the Origin of Life, and the National Science Foundation. Vázquez-Salazar acknowledges support through the NASA Postdoctoral Program, which is administered by Oak Ridge Associated Universities under contract with NASA.
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      Last Updated Nov 21, 2024 EditorWilliam SteigerwaldContactNancy N. Jonesnancy.n.jones@nasa.govLocationGoddard Space Flight Center Related Terms
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      Curiosity Navigation Curiosity Home Mission Overview Where is Curiosity? Mission Updates Science Overview Instruments Highlights Exploration Goals News and Features Multimedia Curiosity Raw Images Images Videos Audio Mosaics More Resources Mars Missions Mars Sample Return Mars Perseverance Rover Mars Curiosity Rover MAVEN Mars Reconnaissance Orbiter Mars Odyssey More Mars Missions The Solar System The Sun Mercury Venus Earth The Moon Mars Jupiter Saturn Uranus Neptune Pluto & Dwarf Planets Asteroids, Comets & Meteors The Kuiper Belt The Oort Cloud 3 min read
      Sols 4368-4369: The Colors of Fall – and Mars
      This image shows all the textures — no color in ChemCam remote-imager images, though — that the Martian terrain has to offer. This image was taken by Chemistry & Camera (ChemCam) aboard NASA’s Mars rover Curiosity on Nov. 18, 2024 — sol 4367, or Martian day 4,367 of the Mars Science Laboratory mission — at 02:55:09 UTC. NASA/JPL-Caltech/LANL Earth planning date: Monday, Nov. 18, 2024
      I am in the U.K., where we are approaching the time when trees are just branches and twigs. One tree that still has its full foliage is my little quince tree in my front garden. Its leaves have turned reddish-brown with a hint of orange, fairly dark by now, and when I passed it this afternoon on my way to my Mars operations shift, I thought that these leaves have exactly the colors of Mars! And sure enough, today’s workspace is full of bedrock blocks in the beautiful reddish-brown that we love from Mars. But like that tree, it’s not just one color, but many different versions and patterns, all of many reddish-brown and yellowish-brown colors.
      The tree theme continues into the naming of our targets today, with ChemCam observing the target “Big Oak Flat,” which is a flat piece of bedrock with a slightly more gray hue to it. “Calaveras,” in contrast, looks a lot more like my little tree, as it is more reddish and less gray. It’s also a bedrock target, and APXS and MAHLI are observing this target, too. APXS has another bedrock target, called “Murphys” on one of the many bedrock pieces around. MAHLI is of course documenting Murphys, too. Let’s just hope that this target name doesn’t get any additions to it but instead returns perfect data from Mars!
      ChemCam is taking several long-distance remote micro-imager images — one on the Gediz Vallis Ridge, and one on target “Mono Lake,” which is also looking at the many, many different textures and stones in our surroundings. The more rocks, the more excited a team of geologists gets! So, we are surely using every opportunity to take images here!
      Talking about images… Mastcam is taking documentation images on the Big Oak Flat and Calaveras targets, and a target simply called “trough.” In addition, there are mosaics on “Basket Dome” and “Chilkoot,” amounting to quite a few images of this diverse and interesting terrain! More images will be taken by the navigation cameras for the next drive — and also our Hazcam. We rarely talk about the Hazcams, but they are vital to our mission! They look out from just under the rover belly, forward and backward, and have the important task to keep our rover safe. The forward-looking one is also great for planning purposes, to know where the arm can reach with APXS, MAHLI, and the drill. To me, it’s also one of the most striking perspectives, and shows the grandeur of the landscape so well. If you want to see what I am talking about, have a look at “A Day on Mars” from January of this year.
      Of course, we have atmospheric measurements in the plan, too. The REMS sensor is measuring temperature and wind throughout the plan, and Curiosity will be taking observations to search for dust devils, and look at the opacity of the atmosphere. Add DAN to the plan, and it is once again a busy day for Curiosity on the beautifully red and brown Mars. And — hot off the press — all about another color on Mars: yellowish-white!
      Written by Susanne Schwenzer, Planetary Geologist at The Open University
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      An artist’s concept of SpaceX’s Starship Human Landing System (HLS) on the Moon. NASA is working with SpaceX to develop the Starship HLS to carry astronauts from lunar orbit to the Moon’s surface and back for Artemis III and Artemis IV. Starship HLS is roughly 50 meters tall, or about the length of an Olympic swimming pool. SpaceX This artist’s concept depicts a SpaceX Starship tanker (bottom) transferring propellant to a Starship depot (top) in low Earth orbit. Before astronauts launch in Orion atop the agency’s SLS (Space Launch System) rocket, SpaceX will launch a storage depot to Earth orbit. For the Artemis III and Artemis IV missions, SpaceX plans to complete propellant loading operations in Earth orbit to send a fully fueled Starship Human Landing System (HLS) to the Moon. SpaceX An artist’s concept shows how a crewed Orion spacecraft will dock to SpaceX’s Starship Human Landing System (HLS) in lunar orbit for Artemis III. Starship HLS will dock directly to Orion so that two astronauts can transfer to the lander to descend to the Moon’s surface, while two others remain in Orion. Beginning with Artemis IV, NASA’s Gateway lunar space station will serve as the crew transfer point. SpaceX The artist’s concept shows two Artemis III astronauts preparing to step off the elevator at the bottom of SpaceX’s Starship HLS to the Moon’s surface. At about 164 feet (50 m), Starship HLS will be about the same height as a 15-story building. (SpaceX)The elevator will be used to transport crew and cargo between the lander and the surface. SpaceX NASA is working with U.S. industry to develop the human landing systems that will safely carry astronauts from lunar orbit to the surface of the Moon and back throughout the agency’s Artemis campaign.
      For Artemis III, the first crewed return to the lunar surface in over 50 years, NASA is working with SpaceX to develop the company’s Starship Human Landing System (HLS). Newly updated artist’s conceptual renders show how Starship HLS will dock with NASA’s Orion spacecraft in lunar orbit, then two Artemis crew members will transfer from Orion to Starship and descend to the surface. There, astronauts will collect samples, perform science experiments, and observe the Moon’s environment before returning in Starship to Orion waiting in lunar orbit. Prior to the crewed Artemis III mission, SpaceX will perform an uncrewed landing demonstration mission on the Moon.
      NASA is also working with SpaceX to further develop the company’s Starship lander to meet an extended set of requirements for Artemis IV. These requirements include landing more mass on the Moon and docking with the agency’s Gateway lunar space station for crew transfer.
      The artist’s concept portrays SpaceX’s Starship HLS with two Raptor engines lit performing a braking burn prior to its Moon landing. The burn will occur after Starship HLS departs low lunar orbit to reduce the lander’s velocity prior to final descent to the lunar surface. SpaceX With Artemis, NASA will explore more of the Moon than ever before, learn how to live and work away from home, and prepare for future human exploration of Mars. NASA’s SLS (Space Launch System) rocket, exploration ground systems, and Orion spacecraft, along with the human landing system, next-generation spacesuits, Gateway lunar space station, and future rovers are NASA’s foundation for deep space exploration.
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      256.544.0034  
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    • By NASA
      5 Min Read Making Mars’ Moons: Supercomputers Offer ‘Disruptive’ New Explanation
      A NASA study using a series of supercomputer simulations reveals a potential new solution to a longstanding Martian mystery: How did Mars get its moons? The first step, the findings say, may have involved the destruction of an asteroid. 
      The research team, led by Jacob Kegerreis, a postdoctoral research scientist at NASA’s Ames Research Center in California’s Silicon Valley, found that an asteroid passing near Mars could have been disrupted – a nice way of saying “ripped apart” – by the Red Planet’s strong gravitational pull.
      The team’s simulations show the resulting rocky fragments being strewn into a variety of orbits around Mars. More than half the fragments would have escaped the Mars system, but others would’ve stayed in orbit. Tugged by the gravity of both Mars and the Sun, in the simulations some of the remaining asteroid pieces are set on paths to collide with one another, every encounter further grinding them down and spreading more debris. 
      Many collisions later, smaller chunks and debris from the former asteroid could have settled into a disk encircling the planet. Over time, some of this material is likely to have clumped together, possibly forming Mars’ two small moons, Phobos and Deimos.
      To assess whether this was a realistic chain of events, the research team explored hundreds of different close encounter simulations, varying the asteroid’s size, spin, speed, and distance at its closest approach to the planet. The team used their high-performance, open-source computing code, called SWIFT, and the advanced computing systems at Durham University in the United Kingdom to study in detail both the initial disruption and, using another code, the subsequent orbits of the debris.
      In a paper published Nov. 20 in the journal Icarus, the researchers report that, in many of the scenarios, enough asteroid fragments survive and collide in orbit to serve as raw material to form the moons. 
      “It’s exciting to explore a new option for the making of Phobos and Deimos – the only moons in our solar system that orbit a rocky planet besides Earth’s,” said Kegerreis. “Furthermore, this new model makes different predictions about the moons’ properties that can be tested against the standard ideas for this key event in Mars’ history.”
      Two hypotheses for the formation of the Martian moons have led the pack. One proposes that passing asteroids were captured whole by Mars’ gravity, which could explain the moons’ somewhat asteroid-like appearance. The other says that a giant impact on the planet blasted out enough material – a mix of Mars and impactor debris – to form a disk and, ultimately, the moons. Scientists believe a similar process formed Earth’s Moon.
      The latter explanation better accounts for the paths the moons travel today – in near-circular orbits that closely align with Mars’ equator. However, a giant impact ejects material into a disk that, mostly, stays close to the planet. And Mars’ moons, especially Deimos, sit quite far away from the planet and probably formed out there, too. 
      “Our idea allows for a more efficient distribution of moon-making material to the outer regions of the disk,” said Jack Lissauer, a research scientist at Ames and co-author on the paper. “That means a much smaller ‘parent’ asteroid could still deliver enough material to send the moons’ building blocks to the right place.”
      It’s exciting to explore a new option for the making of Phobos and Deimos – the only moons in our solar system that orbit a rocky planet besides Earth’s.
      Jacob Kegerreis
      Postdoctoral research scientist at NASA’s Ames Research Center
      Testing different ideas for the formation of Mars’ moons is the primary goal of the upcoming Martian Moons eXploration (MMX) sample return mission led by JAXA (Japan Aerospace Exploration Agency). The spacecraft will survey both moons to determine their origin and collect samples of Phobos to bring to Earth for study. A NASA instrument on board, called MEGANE – short for Mars-moon Exploration with GAmma rays and Neutrons – will identify the chemical elements Phobos is made of and help select sites for the sample collection. Some of the samples will be collected by a pneumatic sampler also provided by NASA as a technology demonstration contribution to the mission. Understanding what the moons are made of is one clue that could help distinguish between the moons having an asteroid origin or a planet-plus-impactor source.
      Before scientists can get their hands on a piece of Phobos to analyze, Kegerreis and his team will pick up where they left off demonstrating the formation of a disk that has enough material to make Phobos and Deimos. 
      “Next, we hope to build on this proof-of-concept project to simulate and study in greater detail the full timeline of formation,” said Vincent Eke, associate professor at the Institute for Computational Cosmology at Durham University and a co-author on the paper. “This will allow us to examine the structure of the disk itself and make more detailed predictions for what the MMX mission could find.”  
      For Kegerreis, this work is exciting because it also expands our understanding of how moons might be born – even if it turns out that Mars’ own formed by a different route. The simulations offer a fascinating exploration, he says, of the possible outcomes of encounters between objects like asteroids and planets. These events were common in the early solar system, and simulations could help researchers reconstruct the story of how our cosmic backyard evolved. 
      This research is a collaborative effort between Ames and Durham University, supported by the Institute for Computational Cosmology’s Planetary Giant Impact Research group. The simulations used were run using the open-source SWIFT code, carried out on the DiRAC (Distributed Research Utilizing Advanced Computing) Memory Intensive service (“COSMA”), hosted by Durham University on behalf of the DiRAC High-Performance Computing facility.
      For news media:
      Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.
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      Last Updated Nov 20, 2024 Related Terms
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