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NASA’s persistence rover may have found a crucial clue central to its mission on Mars: geological evidence that could suggest life existed on the red planet billions of years ago.
The robotic probe came across a veneer-filled red rock on July 18 that appears to be scattered with leopard spots. The mottling may indicate that ancient chemical reactions that occurred within the rock once supported microbial organisms.
“These spots are a big surprise,” David Flannery, a member of NASA’s persistence science team and an astronomer at the Queensland University of Technology in Australia, said in a statement. “On Earth, these features in rocks are often associated with the fossil record of microbes living in the subsurface.”
It is still preliminary research, and NASA scientists have not yet confirmed how the rock was formed, which would require studying it on Earth. But the arrowhead specimen could help the Perseverance team unlock whether Mars was once a planet that was hospitable to life.
“We are very happy to have this sample in the bag!” Briony Horgan, co-investigator of the Persistence rover mission and professor of planetary science at Purdue University in West Lafayette, Indiana, said in an email.
“This rock is exactly the kind of sample we came to Mars to get, and we can’t wait to get it into our labs back here on Earth,” she said. “This is exactly the type of potential microbial biosignature envisioned when NASA designed the Mars 2020 mission, and we used every tool in our payload to find and understand this rock.”
Download the search for signs of ancient life on Mars
The rock, nicknamed Cheyava Falls as one of the falls of the Great Canyon, intrigues scientists for several reasons.
White veins of calcium sulfate present clear evidence that water – vital to life – once passed through the rock. The rover used its Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals, or SHERLOC, instrument to identify carbon-based organic molecules within the rocks.
And the irregular-shaped leopard spots, tested by the rover’s PIXL instrument, short for Planetary Instrument for X-ray Lithochemistry, detected iron and phosphate within the features, said Morgan Cable, a research scientist on the rover team, in a video shared by NASA’s Jet Propulsion Laboratory in Pasadena, California.
“We’ve never seen these three things together on Mars before,” Cable said.
The team also saw the possible presence of hematite between the white bands of calcium sulfate in the rock. Hematite is one of the minerals responsible for Mars’ signature red hue.
The leopard spotting may have occurred when chemical reactions with hematite turned the rock from red to white, which could release iron and phosphate and form the black rings. Such reactions can also provide a source of energy for microbes.
“Cheyava Falls is the most obscure, complex and potentially important rock that Persistence has yet investigated,” said Ken Farley, Persistence project scientist and professor of geochemistry at the California Institute of Technology in Pasadena. in a statement.
The team found millimeter-sized crystals of olivine within the same rock. Olivine, previously detected in another part of the crater at Persistence, is a mineral that forms from magma. The olivine present in the Cheyava Falls rock may be related to rocks that formed elsewhere in the valley, according to the team.
The rover team is grappling with many questions as they study the rock and try to find out what processes could have made it.
Cheyava Falls may have started as a mixture of deposited mud and organic compounds that eventually cemented into rock. Later, water may have penetrated through cracks in the rock, depositing minerals to create the calcium sulfate veins and leopard spots.
But it is also possible that the olivine and sulfate became part of the rock due to scorching hot temperatures on Mars, causing a non-biological chemical reaction that created the leopard spots.
Exploring the history of Mars
Since landing on Mars, Perseverance has traversed Jezero Crater and explored an ancient river delta in search of micro-fossils of past life. The rover is collecting samples along the way that could be sent back to Earth through future missions.
Later, Persistence is exploring the northern edge of Neretva Vallis, an ancient river valley that once delivered water into Jezero Crater more than 3 billion years ago, and that’s where he saw Cheyava Falls. The rover landed inside the crater to explore the ancient site of the lake in February 2021.
Geologists on the Endurance Rover team were keen to study rocks that were formed or altered by water on Mars in the past, which is why Cheyava Falls intrigued them.
“We designed the path for Persistence to make sure it goes to areas where there is the potential for interesting scientific samples,” Nicola Fox, associate administrator for NASA’s Science Mission Directorate, said in a statement. “This trip through the Neretva Vallis river bed paid off because we found something we had never seen before, which will give our scientists so much to study.”
The hard road to life proof
In April, NASA said the original complex, elaborate design for the proposed program to return Endurance samples to Earth, known as Mars Sample Return, was no longer feasible in its current architecture due to budget cuts and delayed return date.
The agency opened a call for NASA centers and industry to develop a new plan that combines innovation and lessons learned from proven technology. NASA leadership hopes to return the samples to Earth by the 2030s with less complexity, cost and risk than originally planned, and the agency is hoping for answers about the best way. to bring back samples from Mars by fall, a NASA administrator said. Bill Nelson during a news conference in April.
Meanwhile, Persistence continues its vital investigative work on Mars and will soon begin climbing the rim of Jezero Crater.
“This discovery comes at a critical time, and NASA is rethinking how best to get these samples back from Mars through the Mars Sample Return,” Horgan said. “It shows how important and unique our set of samples is and how much we could learn about the beginnings of life on Earth-like planets. It also feels very fitting that Jezero threw us one last surprise before we left the ancient river and lake sediments on the crater floor and began climbing the rim.”
The Persistence team says that returning the samples is the only way to know if life ever existed on Mars.
“We’ve zapped that rock with lasers and X-rays and imaged it literally day and night from almost every angle imaginable,” Farley said. “Scientifically, Persistence has nothing else to offer. To fully understand what happened in the Martian river valley at Jezero Crater billions of years ago, we want to bring the sample of Cheyava Falls back to Earth, so that it can be studied with the powerful tools that available in laboratories.”
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