Mars: Jezero Crater rocks older than Earth show water signs, life clues

Billions of years ago, Mars may have been a very different world. Planetary scientists are advancing in unlocking the secrets of the ancient Red Planet, thanks to the Perseverance rover.

In its exploration of Mars, the rover has focused on Jezero Crater, a region thought to have been shaped by water in the past.

Now, new evidence from a joint MIT-NASA study suggests it was most likely a watery oasis.

Presence of carbonates

In 2022, the rover collected seven rock samples from a fan-shaped delta on the crater’s western slope. The Perseverance science team and MIT scientists analyzed the rover’s images and chemical data from the samples.

Moreover, the team calculated grain size and mineral content from the image data.

This showcased that the rocks contain minerals typically formed in water, suggesting they were deposited or formed in a watery environment. They discovered carbonates in the sediments, which are minerals that develop when water precipitates.

On Earth, carbonates are known to make reefs. Moreover, these minerals are considered ideal for preserving microscopic fossils.

This discovery strengthens the hypothesis that Jezero Crater was once home to a vast lake. While experts don’t know how long this watery paradise lasted, conditions were likely suitable for life to potentially emerge.

“These rocks confirm the presence, at least temporarily, of habitable environments on Mars,” said Tanja Bosak, the study’s lead author and professor of geobiology in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).

“What we’ve found is that indeed there was a lot of water activity. For how long, we don’t know, but certainly for long enough to create these big sedimentary deposits,” added Bosak in the press release.

Rocks older than life on Earth

Interestingly, these rocks might be older than the earliest signs of life on Earth. The team suggests these rocks may have been deposited in the ancient lake about 3.5 billion years ago.

“These are the oldest rocks that may have been deposited by water, that we’ve ever laid hands or rover arms on,” said Benjamin Weiss, co-author. “That’s exciting because it means these are the most promising rocks that may have preserved fossils and signatures of life.”

Apart from carbonates, the researchers identified sulfates in certain samples. This suggests the presence of highly saline water in the crater at some point.

A completely salty crater would be inhospitable to life. However, if only the lake’s bottom was salty, it could be beneficial for preserving life forms from the less saline upper layers that might have sunk to the bottom.

“However salty it was, if there were any organics present, it’s like pickling something in salt,” Bosak added. “If there was life that fell into the salty layer, it would be very well-preserved.”

The rover’s instruments have not detected definitive evidence of organic matter in these rock samples. Organic matter is often associated with life, but it can also be created through non-biological geological processes.

Nevertheless, scientists believe these mineral-rich rocks are the best bet for discovering traces of past Martian life. They hope that the Mars Sample Return mission will enable an in-depth study of these rocks on Earth.

The findings were published in the journal AGU Advances.