According to NASA scientists, the Perseverance rover has acquired some of the most critical materials yet on its quest to establish if life ever existed on Mars while investigating the location of an old river delta.
A couple of the freshly acquired samples contain organic debris, indicating that 3.5 billion years ago, Jezero Crater, which presumably previously hosted a lake and the delta that poured into it, had potentially livable habitats.
"The rocks we've been looking at in the delta contain the highest concentration of organic materials that we've observed on the expedition," said Ken Farley, Perseverance project scientist at the California Institute of Technology in Pasadena.
The rover's mission, which began 18 months ago on Mars, involves searching for clues of ancient microbial life. Perseverance is being used to collect rock samples that may have maintained these detectable biosignatures. The rover now has 12 rock samples.
In the 2030s, a series of missions known as Mars Sample Return will return the collection to Earth.
Exploring the delta
Because of the delta's location, NASA scientists are particularly interested in Jezero Crater, which spans 28 miles (45 kilometers). The fan-shaped geological formation, which formerly existed where a river met a lake, preserves layers of Martian history in sedimentary rock created as particles fused together in this formerly water-filled environment.
The rover explored the crater floor and discovered igneous, or volcanic, rock. Perseverance has discovered rich sedimentary rock layers that add to the tale of Mars' ancient temperature and ecosystem during its second mission to examine the delta over the last five months.
"The delta, with its various sedimentary materials, contrasts well with the volcanic rocks located on the crater floor, which were created by magma crystallization," Farley added.
"This juxtaposition offers us with a deep understanding of the geologic history after the formation of the crater, as well as a diversified sample suite. For example, we discovered a sandstone containing grains and rock pieces formed distant from Jezero Crater."
The mission crew dubbed one of the rocks analyzed by Perseverance Wildcat Ridge. The granite was most likely produced billions of years ago when mud and sand settled in a saltwater lake as it drained. The rover scraped away at the rock's surface before analyzing it with the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals, or SHERLOC.
According to Sunanda Sharma, a SHERLOC scientist at NASA's Jet Propulsion Laboratory in Pasadena, this rock-zapping laser acts as a sophisticated black light to expose chemicals, minerals, and organic materials.
The study of the instrument indicated that the organic minerals are most likely aromatics, or stable carbon and hydrogen molecules linked to sulfates. Sulfate minerals, which are frequently found sandwiched between layers of sedimentary rocks, maintain information about the aqueous settings in which they developed.
Organic molecules, such as carbon, hydrogen, and oxygen, as well as nitrogen, phosphorus, and sulfur, are of importance on Mars because they are the building blocks of life. Some organic compounds do not require life to exist since they may be produced by chemical processes.
"While the discovery of this class of organics does not prove that life existed conclusively, this collection of data does begin to resemble some of the things we've observed here on Earth," Sharma explained. "Simply defined, organic matter is a hint in the search for probable evidence of life on another planet. And as our delta campaign progresses, we're receiving stronger and stronger clues."
Perseverance, as well as the Curiosity rover, have previously discovered organic materials on Mars. This time, though, the discovery happened in a location where life may have once lived.
"The sand, mud, and salts that currently make up the Wildcat Ridge sample were deposited under conditions where life may theoretically have thrived in the distant past," Farley explained.
"The fact that the organic substance was discovered in a sedimentary rock, which is known for retaining remains of early life on Earth, is significant. However, as sophisticated as our equipment aboard Perseverance are, we won't be able to draw any conclusions about what's in the Wildcat Ridge sample until it's returned to Earth for in-depth analysis as part of NASA's Mars Sample Return effort."
Sample return to Earth
The samples obtained thus far are sufficiently diverse from critical places inside the crater and delta that the Perseverance crew is interested in putting part of the collection tubes at a specified spot on Mars in roughly two months, according to Farley.
The rover will continue exploring the delta after dropping off the samples at this cache storage.
Future flights will be able to gather these samples and return them to Earth for study utilizing some of the planet's most sensitive and modern technologies. Perseverance is unlikely to detect unequivocal evidence of life on Mars since the bar of proof for proving existence on another planet is so high, according to Farley.
"I've spent most of my career studying Martian habitability and geology, and I know firsthand the enormous scientific value of returning a properly collected collection of Mars rocks to Earth," said Laurie Leshin, director of NASA's Jet Propulsion Laboratory, in a statement.
"It is simply incredible that we are only weeks away from deploying Perseverance's interesting samples and only years away from getting them to Earth so scientists may analyze them in great detail. We'll learn a lot."
Some of the delta's various rocks were around 65.6 feet (20 meters) apart and convey distinct stories.
Skinner Ridge, a chunk of sandstone, is evidence of rocky debris that was likely brought into the crater from hundreds of kilometers away, signifying stuff that the rover will not be able to visit during its mission. In contrast, Wildcat Ridge maintains traces of clays and sulfates that stacked together and became rock.
Once in labs on Earth, the samples might offer information on potentially livable Martian settings, such as chemical, temperature, and when the material was deposited in the lake.
"I believe it's reasonable to say that these are two of the most critical samples that we will gather on this trip," said Perseverance return sample scientist David Shuster of the University of California, Berkeley.