(CNN) — While investigating the site of an ancient river delta, the Perseverance rover collected some of the most important samples yet on its mission to determine if there was ever life on Mars, according to NASA scientists.
Some of the recently collected samples include organic matter, indicating that Jezero Crater, which likely hosted a lake and the delta that fed into it, had potentially habitable environments 3.5 billion years ago.
“The rocks we’ve investigated in the delta have the highest concentration of organic matter we’ve found so far on the mission,” said Ken Farley, Perseverance project scientist at the California Institute of Technology in Pasadena.
The rover’s mission, which began on the Red Planet 18 months ago, includes searching for signs of ancient microbial life. Perseverance is collecting rock samples that might have preserved these telltale biosignatures. Currently, the rover contains 12 rock samples.
A series of missions called Mars Sample Return will bring the collection to Earth in the 2030s.
examining the delta
The delta’s location makes Jezero Crater, which spans 45 kilometers, of particular interest to NASA scientists. This fan-shaped geological feature, which once occurred at the confluence of a river with a lake, preserves layers of Martian history in sedimentary rock, which formed when particles coalesced in this formerly water-filled environment.
The rover investigated the crater floor and found signs of igneous or volcanic rock. During its second campaign to study the delta in the past five months, Perseverance has found rich layers of sedimentary rock that add to the story of Mars’ ancient climate and environment.
“The delta, with its various sedimentary rocks, contrasts beautifully with the igneous rocks, formed by crystallization of magma, discovered on the crater floor,” Farley said.
“This juxtaposition gives us a rich understanding of the post-crater geological history and diverse sample set. For example, we found a sandstone bearing grains and rock fragments created far from Jezero Crater.”
The mission team dubbed one of the rocks Perseverance sampled Wildcat Ridge. The rock probably formed when mud and sand settled in a saltwater lake as it evaporated billions of years ago. The rover scraped the rock surface and analyzed it with an instrument known as Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals, or SHERLOC.
This rock-scanning laser works like an elegant black light to discover chemicals, minerals and organic matter, said Sunanda Sharma, a SHERLOC scientist at NASA’s Jet Propulsion Laboratory in Pasadena.
The instrument’s analysis revealed that the organic minerals are likely aromatic, or stable molecules of carbon and hydrogen, which are connected to sulfates. Sulfate minerals, often found between layers of sedimentary rocks, retain information about the aquatic environments in which they formed.
Organic molecules are interesting on Mars because they represent the building blocks of life, such as carbon, hydrogen, and oxygen, as well as nitrogen, phosphorus, and sulfur. Not all organic molecules need life to form, since some can be created by chemical processes.
“Although the detection of this class of organics alone doesn’t definitively mean that there was life there, this set of observations is starting to look like some things we’ve observed here on Earth,” Sharma said.
“Simply put, if it’s a scavenger hunt for possible signs of life on another planet, organic matter is a clue. And we’re getting stronger and stronger clues as we go through our delta campaign.”
Both Curiosity and Perseverance have found organic matter on Mars before. But this time, the detection occurred in an area where life may have once existed.
“In the distant past, the sand, mud, and salts that now make up the Wildcat Ridge sample were deposited in conditions in which life could have thrived,” Farley said.
“The fact that organic matter was found in such a sedimentary rock, known to preserve fossils of ancient life here on Earth, is important. However, despite the ability of our instruments aboard Perseverance, We will have to wait until the Wildcat Ridge sample is returned to Earth for further study as part of the agency’s Mars Sample Return Campaign to draw more conclusions about its contents.”
Sample return to Earth
The samples collected so far represent such a wealth of diversity in key areas of the crater and delta that the Perseverance team is interested in depositing some of the sample tubes at a designated location on Mars in about two months, Farley said.
Once the rover deposits the samples in this deposit, it will continue to explore the delta.
Future missions will be able to collect these samples and return them to Earth for analysis using some of the most sensitive and advanced instruments on the planet. Perseverance is unlikely to find incontrovertible evidence for life on Mars because the burden of proof to establish it on another planet is so high, Farley said.
“I have studied Martian habitability and geology for much of my career and I know firsthand the incredible scientific value of returning a carefully collected set of Mars rocks to Earth,” said Laurie Leshin, director of the Jet Propulsion Laboratory. NASA, in a statement.
“That we are weeks away from displaying Perseverance’s fascinating samples and just a few years away from bringing them back to Earth so scientists can study them in exquisite detail is truly phenomenal. We will learn a lot.”
Some of the various rocks in the delta were about 20 meters apart, each telling a different story.
A chunk of sandstone, called Skinner Ridge, is evidence of rocky material that was likely transported into the crater from hundreds of miles away, representing material the rover will not be able to travel to during its mission. Wildcat Ridge, meanwhile, retains evidence of clays and sulfates that overlaid and formed the rock.
Once the samples are in labs on Earth, they could reveal information about potentially habitable Martian environments, such as chemistry, temperature, and when material was deposited in the lake.
“I think it’s safe to say that these are two of the most important samples that we will collect on this mission,” said David Shuster, Perseverance sample return scientist at the University of California, Berkeley.