Ancient Mars had all the right ingredients for life 3.5 billion years ago, but if life actually swam, dug, or floundered on the Red Planet in the ancient past, it will be necessary to bring Martian rocks to Earth for the analyses.
That was the consensus of NASA scientists behind the space agency’s Perseverance rover mission during a public presentation on the mission’s findings on Thursday.
Since landing on Mars in 2021, Perseverance has drilled rock samples for analysis in what was once a vast lake on Mars. Those samples have now revealed the presence of both ancient liquid water and organic molecules, the chemical building blocks of life.
“If these conditions have existed, I think pretty much anywhere on Earth at any time over the last, let’s call it three and a half billion years,” Ken Farely, Perseverance project scientist at the presentation, “I think it’s safe let’s say or at least suppose biology would have done its homework and left its mark on these rocks for us to observe.
NASA is counting on this: while Perseverance does not have the tools to determine with certainty whether life once existed on Mars, laboratories on Earth do. And NASA plans to bring the rock samples that Perseverance stored in titanium tubes home for analysis in the early 1930s.
The Perseverance rover landed on Mars on February 18, 2021, in Jezero Crater, a 28-mile-wide impact crater that at one point contained a vast lake. Since then, the rover has traveled more than eight miles across the lake’s ancient bottom and to the higher elevations of what was once a river delta, where running water once fed the lake and deposited silt at miles away.
Along the way, Perseverance selected rock drilling cores, analyzing and storing them for recovery from a subsequent sample return mission.
Perseverance scans rocks for organic material using its Scanning Habitable Environments with Raman & Luminescence for Organics Chemicals, or the Sherloc instrument, which uses an ultraviolet laser to scan lumps of any organic material present. Sherloc detected an increasing amount of organic material as it made its way into the ancient Jezero Crater Delta region, NASA Jet Propulsion Laboratory (JPL) astrobiologist Sunanda Sharma said during Thursday’s presentation.
“If this is a scavenger hunt for potential signs of life on another planet, organic matter is a clue and we’re getting stronger and stronger clues as we move through our delta campaign,” he said.
Two recent Perseverance discoveries may prove more valuable than any other discovery so far from the mission.
The rover recently took samples from two rocks, Skinner Ridge and Wildcat Ridge, names taken from locations in the Shenandoah National Park in the United States.
Skinner Rock is a sandstone, made from the layering of many types of rock material brought from miles away and deposited in the river delta, according to David Shuster, scientist of the champion of perseverance. “This is important because it provides us with material from a very distant distance that the rover will not visit on this mission,” he said.
Wildcat Ridge, meanwhile, is a mud-containing clay, which likely formed in salt water when the lake in Jezero Crater evaporated. It also contained a type of organic matter known as aromatic, “which are stable molecules composed of carbon and hydrogen, and sometimes other elements, with ring structures,” said Dr Sharma.
Those aromatic compounds were present in almost every place Sherloc scanned the Wildcat Ride material.
Importantly, WildCat’s crest also contains sulfate, which has implications for the information it could hold about ancient life on Mars, if it existed.
“The organic signals are also more strongly related to a mineral called sulfate that we have seen on the rock,” said Dr. Sharma. “On Earth, sulfate deposits are known to preserve organic substances and can harbor signs of life, which are called biological signatures. This makes these samples and this series of observations partly intriguing ”.
The discovery builds on the results of other NASA missions, including the ongoing mission of the Curiosity rover, which first detected signs of organic compounds in another part of Mars in 2013.
‘Personally, I find these results so moving,’ said Dr Sharma, ‘because it seems like we are in the right place with the right tools at a very crucial time.’
Neither Perseverance nor Curiosity contain enough instrumentation to determine with certainty whether or not life ever existed on Mars, but terrestrial laboratories could. This is why Perseverance collected rock samples and stored them in tubes for recovery by the European Space Agency-NASA joint sample return mission to Mars.
Scheduled for launch in 2028, the sample return mission will collect samples from either deposit on the Martian surface or directly from Perseverance if the rover is still operational. Those champions will return to Earth in 2033.
“We can bring these rocks back to Earth, where we can interrogate them in the most sophisticated labs we have, so we can answer some of the biggest questions we scientists can ask,” JPL Director Laurie Leshin said at the presentation. Whatever the results, “we will learn so much”.