Found On Mars: Rocks ‘Altered by Water’ That Could Contain Traces Of Ancient Life

Did the red planet ever host life? It’s a question that’s hard to answer from 250 million miles away, but NASA’s Perseverance rover may have just gotten closer to the answer.

On Mars since dramatically parachuting in on February 18, 2021, the truck-sized robot is currently exploring the river delta in Jezero crater, but a new paper published today in Science reveals more about the rock samples it’s already collected from the crater’s floor.

Intriguingly, some of them appear to have been geochemically altered by liquid water.

The news comes as NASA and the European Space Agency finalize plans for the Mars Sample Return mission, the first-ever return trip to Mars in 2027 that will bring these very rock samples back to Earth in 2033 for study by astrobiologists.

“These rocks on Mars have been aqueously altered by water, so there are carbonates, iron oxides and salts that have formed within these rocks,” said Amy Williams, an astrobiologist and professor of geology at the University of Florida and one of the planners for the Perseverance mission. “Those provide different geochemical micro-environments that organisms could exploit if they were present.”

Though it’s now dry, cold and has high radiation, Jezero crater was once home to a lake, possibly for millions of years. Was it habitable? Scientists believe that, yes, a watery Mars could have supported life billions of years ago.

The hunt for biosignatures

These samples from Perseverance’s first science campaign show a crater floor that has eroded much more than expected, revealing igneous rocks formed by lava and magma. Perseverance’s scientists had expected to find only the softer sedimentary rocks that would have made up the lake bed.

This is a bonus because the igneous rocks discovered—specifically the samples from formations called Máaz and Séítah—likely predate the river delta.

“The aqueous alteration of the minerals has the potential to record biosignatures,” said Williams. Biosignatures are evidence for past or present life. “We have organisms on Earth that live in very similar kinds of rocks,” said Williams.

We’re talking microorganisms like bacteria and archaea, which are capable of living in extreme environments all over Earth. “Some microorganisms live in, and on, igneous rocks like those we characterized in the Jezero crater floor,” said Williams. “Some of these organisms even live kilometers down in the subsurface!”

When was Mars wet?

“Our best guess is that water started to dry up 3.8 to 3.5 billion years ago,” said Williams about Jezero Crater. However, the error bar is big. From the NASA Curiosity rover’s exploration of Gale crater scientists think its lake may have been active for millions to tens of millions of years.

“The really exciting thing is that the return of these samples from Jezero will give us samples to age date,” said Williams. “These will give us brackets on when the delta formed, how long it was active and when water—at least at Jezero—dried up. These findings are going to be profound!”

Mars Sample Return: the plan

It’s a mission with options. NASA doesn’t know how long Perseverance will keep going on Mars, so for now the rover is free to go collect 10 samples or so and leave them in a cache in Jezero Crater for a rocket-equipped lander to come pick them up. The worst case scenario is that scientists will get its samples. Just incase Perseverance can’t help out a couple of Ingenuity-class Mars Helicopters will make the trip, too.

However, Perseverance is actually doubling-up on its samples. So while it will lay one set in Jezero Crater, the plan is for Perseverance to travel outside of the crater to a place called Midway. If it makes it there, and manages to collect another 20 or so samples, it can deliver them direct to the lander a much larger collection of samples from a wider suite of environments. Even it it doesn’t survive that long, the lander will be able to land just 50ft. from wherever the most interesting cache of samples exists—either in Jezero crater or outside of it.

Beyond Jezero

“So far the only information we have about those rocks is what we can detect about texture and mineralogy from orbital observations,” said Williams. So far geologists have found basement rock and large rock fragments possibly from meteor strikes that caused Jezero. “There will be far more diversity and nuance discovered in these units once we have our wheels on the ground outside of Jezero,” said Williams. “Before then Perseverance is exploring the Jezero delta, which is made up of sedimentary rocks.”

Once back on Earth they will help scientists establish a geological record crucial in understanding Mars’s environmental evolution and possibly its prebiotic chemistry and biology.

Wishing you clear skies and wide eyes.