NASA’s Perseverance rover found a new possible environment for Martian life

WASHINGTON DC – The Perseverance rover on Mars may have encountered the oldest rocks humans have ever seen and, possibly, evidence of a new environment that ancient Martian organisms could have inhabited, if they ever existed.

“That’s really one of the most exciting things this mission will do, is look at rocks that formed so early in the history of the solar system,” Caltech geochemist Kenneth Farley said during a Dec. 12 news conference at. a meeting of the American Geophysical Union. “Almost the dawn of the solar system.”

Probably the oldest rocks we’ve seen

For most of its mission, Perseverance has been poking around inside Jezero Crater, probing and sampling rocks that are probably about 3.7 billion years old (SN: 17.2.23). The rocks on the rim, however, are probably much older, having been uplifted by the impact that created the crater.

On Dec. 11 — after a slippery, three-month climb 500 meters from the crater floor — the robotic explorer finally crossed the rim of that crater, after weeks of studying the geology of the high area. And all that exploration seems to have paid off.

“The rocks we’re exploring now are older than 4 billion years,” said Farley, who is also the project scientist for the Mars 2020 Mission that brought the rover to the planet. “These are among the oldest rocks in the solar system and are older than any rock that exists on Earth.” Part of the reason for this is that much of Earth’s ancient surface was destroyed at subduction zones, where one tectonic plate sinks beneath another to descend into the mantle (SN: 1/13/21).

At the top of the crater, Persistence traveled through an area known as the Pico Turquino Hills, where he captured images of numerous outcrops. “What we found in these relatively small outcrops is that the rocks are extremely different, and it appears that each of the hills that make up the Pico Turquino Hills has a distinct assemblage of mostly igneous minerals, with some variations from water,” Farley. said. “These are possible pieces of the earliest crust of Mars.”

The instruments aboard Perseverance cannot precisely date the rocks. Instead, researchers are basing their age estimates on current understanding of crater formation and the history of Mars. “Those are our best estimates, but they’re only estimates,” Farley said. “That’s one of the reasons we want to do the sample return.”

If the newly encountered Martian rocks are indeed that old, they may contain information about how rocky planets like Mars and Earth evolved in their early days (SN: 16.3.17). “For us to understand how rocky planets behave in the first, say, half a billion years, [we] can’t do that from Earth,” Farley said.

A possible new environment for Martian life

Ancient rocks were not all that Perseverance found in the Pico Turquino Hills. The rover also encountered evidence of an entirely new habitable environment for possible Martian life (SN: 15.7.24): a field of “brilliant white, the size of a melon [stones]and instruments on board the rover confirm that these cobbles are pure quartz,” Farley said. “This has never been seen before” on Mars.

Quartz forms where hot fluids flow through rocks, and sometimes at temperatures that are habitable. These rocks may have formed in an environment similar to a hot spring, and we know those environments can support life on Earth, so perhaps something similar once existed on Mars, Farley said. “This is a potentially habitable environment that is completely different from the habitable environments Perseverance probed on the crater floor.”

According to Farley, the goal is now to look for quartz where it is still embedded in the Martian surface so that it can be sampled. “Neither our drill nor our corroder can work in such freedom, [cobblestone-sized rocks]Farley said. “The rock would just move out of the way if we tried to work on it.” Finding more accessible quartz could also help researchers better understand how the mineral fits into the rest of the Martian rock record.

Next stop, Witch Hazel Hill

Moving from the Pico Turquino Hills, Perseverance will spend the next six months exploring an area called Witch Hazel Hill. Located away from the crater, the rocks at Witch Hazel Hill should be more representative of the geology of the broader region, planetary scientist and geologist Candice Bedford of Purdue University in West Lafayette, Ind., said at the news conference.

Additionally, NASA’s Mars orbiters have already identified extensive outcrops of layered rock at Witch Hazel Hill. “As geologists we love layered outcrops,” Bedford said. “For us, each preserved layer is like, as we look down through it, it’s like turning a [page in the book] of Martian history.”