NASA’s rock-hunting rover reveals surprising geology of Martian craters

Will Dunham

WASHINGTON (Reuters) – Core samples drilled by NASA’s Perseverance rover on the surface of Mars have revealed the geology of a massive impact crater that scientists suspect may have hosted microbial life billions of years ago, including understanding of the nature of the rocks there. of surprise.

Samples obtained by the car-sized six-wheeled robotic rover and stored for future transport to Earth for further study showed that the rocks from four sites within Jezero Crater were igneous—formed by the cooling of molten material. The rocks also have evidence of changes due to exposure to water, another sign that Mars was warm and humid long ago when cold and arid.

Scientists think the rock, which formed about 3.5 billion years ago, may have been sedimentary, formed from sediment deposited in the lake bed.

“In fact, we found no evidence of the rover exploring sedimentary rocks at the bottom of the crater, even though we know there was once a lake in the crater and the sediments must have been deposited. These sediments must have been eroded away,” Caltech Geochemistry Home Kenneth said Farley was the lead author of one of four studies published in the journals Science and Science Advances describing the geology of the crater.

Perseverance arrived on Mars in February 2021 and has been busy working in Jezero Crater since then, using a suite of instruments scientists are exploring whether Earth’s closest planetary neighbor ever had conditions conducive to life.

It is collecting rock samples about the size of blackboard chalk that will be recovered by a spacecraft in 2033 and brought to Earth for further examination, including biosignatures — indicators of life.

Jezero Crater is 28 miles (45 kilometers) wide and lies north of the Martian equator. The area appears to have been rich in water once, and was home to a river delta that overflowed the crater wall to form a large lake. Scientists suspect the crater may harbor microbial life, and evidence may be contained in lake bed or shoreline rocks.

Perseverance is now collecting samples in the delta area.

Igneous rocks in the crater have been found to interact with water, creating new minerals and depositing salt, although this water is apparently either low in content or not long-lived – possibly groundwater. But the presence of the water suggests it might have been a habitable environment at the time, the researchers said.

NASA planetary sample scientist Yang Liu said: “We have collected samples that will return to Earth and they should provide key evidence of what, if any, organisms inhabited the bottom of Jezero Crater when rocks interacted with water. .” Jet Propulsion Laboratory and lead author of one of the studies.

The four samples were drilled from two areas, one called Seitah and the other called Maaz. The Seitah rock appears to have formed underground through the slow cooling of thick magma. Maaz rocks may have cooled relatively quickly in the upper layers of subterranean magma or after eruptions at the volcanic surface. Either way, any rock layers that once covered these areas have been eroded away by water or wind.

The Seitah sample is a coarse-grained igneous rock containing olivine minerals, Liu said, noting that three Martian meteorites found on Earth have similar compositions.

Examining samples from Earth may reveal when the rocks formed and provide clearer answers about when liquid water existed on the surface of Mars. Liquid water is a key ingredient of life.

“Understanding when and for how long climatic conditions on Mars allowed liquid water to stabilize is critical to the larger question we’re trying to solve with this mission and sample return — about whether and when life could have existed once billions of years ago. existed on early Mars,” said UC Berkeley geochemist and study co-author David Schuster.

(Reporting by Will Dunhamk, Editing by Rosalba O’Brien)

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