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NASA’s Perseverance rover may have found a crucial clue for its mission to Mars: geological evidence that could suggest life existed on the Red Planet billions of years ago.
On July 18, the rover discovered a vein-filled red rock that appears to be dotted with leopard spots. These spots could indicate that ancient chemical reactions occurring in the rock once harbored microbial organisms.
“These spots are a big surprise,” David Flannery, a member of NASA’s Perseverance science team and an astrobiologist at Queensland University of Technology in Australia, said in a statement. “On Earth, these types of features in rocks are often associated with fossilized traces of microbes living underground.”
The research is still preliminary, NASA scientists have yet to confirm how the rock was created, which would require studying it on Earth. But the arrowhead-shaped specimen could help the Perseverance team determine whether Mars was once a planet suitable for life.
“We are absolutely thrilled to have this sample in the bag!” Briony Horgan, a co-investigator on the Perseverance rover mission and a professor of planetary sciences at Purdue University in West Lafayette, Indiana, said in an email.
“This rock is exactly the type of sample we came to Mars for, and we can’t wait to bring it into our labs here on Earth,” she said. “This is precisely the type of potential microbial biosignature that was envisioned when NASA designed the Mars 2020 mission, and we used every instrument on our payload to find and understand this rock.”
The rock, nicknamed Cheyava Falls after one of the Grand Canyon’s waterfalls, intrigues scientists for a number of reasons.
White veins of calcium sulfate clearly show that water, essential for life, has passed through the rock. The rover used its SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument to identify carbon-based organic molecules present in the rocks.
And the irregularly shaped leopard spots, probed by the rover’s PIXL instrument, short for Planetary Instrument for X-ray Lithochemistry, detected iron and phosphate in the features, Morgan Cable, a research scientist on the rover team, said in a video shared by NASA’s Jet Propulsion Laboratory in Pasadena, California.
NASA/JPL-Caltech/ASU/MSSS
The Perseverance rover has captured a 360-degree panorama of a region of Mars called the “Bright Angel,” where a river flowed billions of years ago.
“We’ve never seen these three things together on Mars before,” Cable said.
The team also spotted the potential presence of hematite between the white bands of calcium sulfate in the rock. Hematite is one of the minerals responsible for Mars’ distinctive red hue.
Leopard spots may be due to chemical reactions with hematite that turned the rock from red to white, which can release iron and phosphate and potentially cause the formation of black rings. Such reactions may also provide an energy source for microbes.
“Cheyava Falls is the most puzzling, complex and potentially important rock ever studied by Perseverance,” Ken Farley, Perseverance project scientist and professor of geochemistry at the California Institute of Technology in Pasadena, said in a statement.
The team also found millimeter-sized olivine crystals in the same rock. Olivine, previously detected in another part of the crater by Perseverance, is a mineral that forms from magma. The olivine in the Cheyava Falls rock may be related to rocks that formed elsewhere in the valley, the team said.
The rover team faces a multitude of questions as it studies the rock and tries to determine what processes might have formed it.
Cheyava Falls may have originally been formed by a mixture of mud and organic compounds deposited together that eventually cemented together to form rock. Later, water was able to penetrate through cracks in the rock, depositing minerals to create the calcium sulfate veins and leopard spots.
But it’s also possible that the olivine and sulfate became incorporated into the rock due to the extremely high temperatures on Mars, causing a non-biological chemical reaction that created the leopard spots.
Since landing on Mars, Perseverance has traversed Jezero Crater and explored an ancient river delta for microfossils of past life. The rover has collected samples along the way that could be brought back to Earth by future missions.
Most recently, Perseverance explored the northern edge of the Neretva Valley, an ancient river valley that once fed water into Jezero Crater more than 3 billion years ago, and that’s where it spotted Cheyava Falls. The rover landed in the crater to explore the site of the ancient lake in February 2021.
NASA/JPL-Caltech/MSSS
Perseverance took this selfie, composed of 62 individual images, on July 23.
Geologists on the rover team were eager to have Perseverance study rocks that were created or altered by water on Mars in the past, which is why the Cheyava Falls intrigued them.
“We designed Perseverance’s route to reach areas with potential for collecting interesting scientific samples,” Nicola Fox, associate administrator for NASA’s Science Mission Directorate, said in a statement. “This trip to the Neretva River bed paid off because we discovered something we’ve never seen before, which will give our scientists plenty of material to study.”
In April, NASA said the original complex, multi-mission design of the program to return Perseverance samples to Earth, called Mars Sample Return, was no longer feasible in its current architecture due to budget cuts and a delayed return date.
The agency has put out a call to NASA centers and industry to develop a new plan that combines innovation with lessons learned from proven technologies. NASA leadership hopes to be able to return samples to Earth by the 2030s with less complexity, cost and risk than originally planned, and the agency hopes to have answers on how best to return samples from Mars by the fall, NASA Administrator Bill Nelson said at a news conference in April.
NASA/JPL-Caltech/ASU/MSSS
Perseverance collected a rock sample from Cheyava Falls on July 21.
Meanwhile, Perseverance continues its crucial survey work on Mars and will soon begin climbing the rim of Jezero Crater.
“This discovery comes at a critical time as NASA reevaluates how best to retrieve these Mars samples via Mars Sample Return,” Horgan said. “It shows how important and unique our sample series is.” and all we might learn about the beginnings of life on Earth-like planets. It also seems fitting that Jezero has one last surprise in store for us before it leaves the ancient river and lake sediments of the crater floor and begins climbing the rim.
The Perseverance team says returning the samples is the only way to know if life ever existed on Mars.
“We’ve treated this rock with lasers and X-rays and photographed it day and night from almost every angle imaginable,” Farley said. “Scientifically, Perseverance has nothing left to offer. To fully understand what really happened in this Martian river valley in Jezero Crater billions of years ago, we would like to bring the Cheyava Falls sample back to Earth, so it can be studied with the powerful instruments available in laboratories.”
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