среда, 13 ноября 2019 г.

NASA's Mars 2020 Will Hunt for Microscopic Fossils

NASA - Mars 2020 Rover logo.

Nov. 12, 2019

Scientists with NASA's Mars 2020 rover have discovered what may be one of the best places to look for signs of ancient life in Jezero Crater, where the rover will land on Feb. 18, 2021.

A paper published today in the journal Icarus identifies distinct deposits of minerals called carbonates along the inner rim of Jezero, the site of a lake more than 3.5 billion years ago. On Earth, carbonates help form structures that are hardy enough to survive in fossil form for billions of years, including seashells, coral and some stromatolites — rocks formed on this planet by ancient microbial life along ancient shorelines, where sunlight and water were plentiful.

Image above: Lighter colors represent higher elevation in this image of Jezero Crater on Mars, the landing site for NASA's Mars 2020 mission. The oval indicates the landing ellipse, where the rover will be touching down on Mars. Image Credits: NASA/JPL-Caltech/MSSS/JHU-APL/ESA.

The possibility of stromatolite-like structures existing on Mars is why the concentration of carbonates tracing Jezero's shoreline like a bathtub ring makes the area a prime scientific hunting ground.

Mars 2020 is NASA's next-generation mission with a focus on astrobiology, or the study of life throughout the universe. Equipped with a new suite of scientific instruments, it aims to build on the discoveries of NASA's Curiosity, which found that parts of Mars could have supported microbial life billions of years ago. Mars 2020 will search for actual signs of past microbial life, taking rock core samples that will be deposited in metal tubes on the Martian surface. Future missions could return these samples to Earth for deeper study.

In addition to preserving signs of ancient life, carbonates can teach us more about how Mars transitioned from having liquid water and a thicker atmosphere to being the freezing desert it is today. Carbonate minerals formed from interactions between carbon dioxide and water, recording subtle changes in these interactions over time. In that sense, they act as time capsules that scientists can study to learn when — and how — the Red Planet began drying out.

Measuring 28 miles (45 kilometers) wide, Jezero Crater was also once home to an ancient river delta. The "arms" of this delta can be seen reaching across the crater floor in images taken from space by satellite missions like NASA's Mars Reconnaissance Orbiter. The orbiter's Compact Reconnaissance Imaging Spectrometer for Mars instrument, or CRISM, helped produce colorful mineral maps of the "bathtub ring" detailed in the new paper.

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