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In 2020, NASA's next rover will depart from Cape Canaveral Air Force Base in Florida and head for the Jezero crater on Mars. Jezero once housed an ancient system of lakes and delta, which scientists say would have captured and preserved information about the evolution of the Red Planet – and, if so, traces of ancient life.
Thomas Zurbuchen, associate director of the NASA Science Mission Director, announced last week his choice among 60 candidates selected for their rich geology dating from 3.6 to 3.9 billion years. The decision has been made for many years and, before the site was finally chosen, scientists from around the world gathered in Glendale, California, to bring their expertise to the last four candidate landing sites during the last of the four workshops at the March 2020 landing sites.
Tanja Bosak, associate professor in the Department of Earth Sciences, Atmosphere and Planets of MIT, was one of those scientists. His work uses experimental geobiology to explore modern biogeochemical and sedimentological processes in microbial systems. For Bosak, the Jezero Crater is the ideal landing site to learn about the potential livability of early March.
"The geology of the crater Jezero is very obvious [from orbit]and it is clear that the environment was livable in the past, "says Bosak. "It is older than any sedimentary environment preserved in the rock record of the Earth. The Jezero crater preserves some of the most ideal types of rocks we use to search for life on Earth. "
Clays and carbonates are minerals known to facilitate the preservation of fossils on Earth. Bosak's work as an investigator in the Simons Collaboration on the Origins of Life (SCOL) contributed to an October workshop conference entitled "In Search of Prebiotic Signatures with the March 2020 Rover" , given by David Catling. Catling is a professor of Earth Sciences and Space at the University of Washington and is also a researcher at SCOL.
In his speech, Catling explained that even if life had never existed on Mars, scientists could determine if prebiotic precursors were still present in the Martian environment – important information to discern the conditions necessary to life.
Roger Summons, Schlumberger Professor of Geobiology at EAPS and SCOL researcher, also contributed to the presentation. As the lead investigator at NASA's Institute for Astrobiology MIT, Foundations of Complex Life, and a member of the Mars sample analysis team using NASA's Curiosity rover, Summons' work on the preservation of organic matter in different environments on Earth and on Mars.
"Through our efforts to trace back the oldest life on Earth, we know that the best chance of finding convincing and credible evidence will come from studies of well-preserved, fine-grained stratified rocks deposited under stagnant water masses ", Invocation said.
Earlier in the year, Bosak and Summons both contributed to "A Field Guide to Fossil Research on Mars," a review article published in the Journal of Geophysical Research this summarizes the strategies behind the search for old biosignatures among the different potentially habitable Martian environments. The authors of the review mentioned the favorability of sedimentary environments very similar to those of the Jezero crater, because analogues of these environments on Earth, such as deltas and lakes, have the greatest potential for collecting and preserving molecular fossils and body microbes.
In fact, organic matter has recently been detected in mudstones dating back 3 billion years ago at the site of an ancient lake at Gale Crater, the Mars Curiosity rover search site. The results, published in Science, has sparked increased interest in the potential preservation of organic matter at other Mars landing sites, including the Jezero crater. Indeed, unlike previous missions on Mars, Mars 2020 mission will not only measure in the Martian environment, it will also collect and cache sediment cores from sites of interest that will then be returned on Earth during a subsequent mission.
"Although the use of imaging and spectroscopy tools that can be used remotely on spacecraft is very useful, nothing is comparable to the sensitivity and specificity of the chemical instrumentation that we can access in laboratories all over the world, "says Summons. "This has been demonstrated time and time again by what has been learned in almost fifty years of studying the rocks that were returned to Earth at the time of Apollo's exploration of the moon."
Bosak is particularly excited about the images and data that the rover will collect during his mission to the Jezero crater. The mission could determine if the carbonates on the edge of the crater are "precipitated out of the lake, as do limestones". On Earth, early Earth limestones can have forms that record microbial interactions with sediments and stimulated by microbes. precipitation of minerals, "says Bosak.
Ben Weiss, Professor of Planetary Science at EAPS, also participated in the March 2020 Landing Site Workshop and introduced co-author Anna Mittelholz, a graduate student at the University of British Columbia, on the possible studies of the magnetic field of Mars.
"Jezero will also be an extremely exciting place to get samples to understand the history of the ancient Martian magnetic field," Weiss said. In the summer, Mittelholz and Weiss published an article in the journal Earth Sciences and Space, "Mars 2020 Candidate Landing Sites: Magnetic Field Perspective", which details the findings they presented at the workshop.
During the course of the Mars planetary evolution, Mars lost its global magnetic field and much of its primitive atmosphere, which could have radically changed the Martian environment. Planetary magnetic fields are generated by the movement of metal fluids in planetary interiors during a process called dynamo. For example, the magnetic field of the Earth is generated and maintained from its molten core and rich in iron.
"The most important problem is to determine when the [Martian] dynamo off. This would help determine whether the loss of the dynamo field caused the transition from a warmer, wetter start to March to the current cold and dry state, he said. "Jezero is a great place to test this hypothesis as it contains rocks and minerals whose duration extends over a period of time until we suspect that the dynamo has gone out."
Overall, mobile exploration and sample collection at the Jezero crater could help refine scientific knowledge in all disciplines.
"Jezero Crater will be a great place to understand the contribution of the dynamo to the protection of the first atmosphere and livability of early March," Weiss said.
This information could also help us understand how and why life has settled on our own planet.
"I think it's as good as possible," says Bosak.
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