Perseverance's New Rock Samples Reveal Water Was Present on Mars For a Long Time

NASA's Mars rover Perseverance collected its second rock sample this week — and Friday Caltech's Ken Farley, a project scientist for the mission, announced that they've learned something.

'It's a big deal that the water was there a long time.'

The Perseverance science team already knew a lake once filled the crater; for how long has been more uncertain. The scientists couldn't dismiss the possibility that Jezero's lake was a 'flash in the pan': floodwaters could have rapidly filled the impact crater and dried up in the space of 50 years, for example. But the level of alteration that scientists see in the rock that provided the core samples — as well as in the rock the team targeted on their first sample-acquisition attempt — suggests that groundwater was present for a long time.

This groundwater could have been related to the lake that was once in Jezero, or it could have traveled through the rocks long after the lake had dried up. Though scientists still can't say whether any of the water that altered these rocks was present for tens of thousands or for millions of years, they feel more certain that it was there for long enough to make the area more welcoming to microscopic life in the past.
And they discovered something interesting in the rock samples: salts.
These salts may have formed when groundwater flowed through and altered the original minerals in the rock, or more likely when liquid water evaporated, leaving the salts. The salt minerals in these first two rock cores may also have trapped tiny bubbles of ancient Martian water. If present, they could serve as microscopic time capsules, offering clues about the ancient climate and habitability of Mars.

Salt minerals are also well-known on Earth for their ability to preserve signs of ancient life.

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