Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific developments and more.
NASA’s Perseverance rover may have found a key clue crucial to its Mars mission: geological evidence that could suggest life existed on the Red Planet billions of years ago.
The robotic explorer on July 18 stumbled upon a red rock with veins that appear to be dotted with leopard spots. The spots could indicate ancient chemical reactions that took place within the rock and once supported microbial organisms.
“These spots are a big surprise,” David Flannery, a member of the NASA Perseverance science team and an astrobiologist at the Queensland University of Technology in Australia, said in a statement. “On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.”
The research is still in its early stages, and NASA scientists haven’t confirmed how the rock formed, meaning they’ll have to study it on Earth. But the arrowhead-shaped specimen could help the Perseverance team figure out whether Mars was once a planet suitable for life.
“We are thrilled to have this monster in the bag!” said Briony Horgan, a co-investigator on the Perseverance rover mission and a professor of planetary sciences at Purdue University in West Lafayette, Indiana, in an email.
“This rock is exactly the type of sample we came to Mars to find, and we can’t wait to get it back to our labs here on Earth,” she said. “This is exactly the type of potential microbial biosignature that was envisioned when NASA designed the Mars 2020 mission, and we’ve used every instrument in our payload to find and understand this rock.”
The search for signs of ancient life on Mars
The rock, nicknamed Cheyava Falls after one of the Grand Canyon’s waterfalls, intrigues scientists for several reasons.
White veins of calcium sulfate provide clear evidence that water — crucial to life — once flowed through the rocks. The rover used its Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals, or SHERLOC, instrument to identify organic carbon-based molecules in the rocks.
And the irregularly shaped leopard spots, tested by the rover’s Planetary Instrument for X-ray Lithochemistry (PIXL), detected iron and phosphate in the features, said Morgan Cable, a researcher 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 discovered the possible presence of hematite between the white bands of calcium sulfate in the rock. Hematite is one of the minerals responsible for the characteristic red color of Mars.
The leopard spots may have been created by chemical reactions with hematite that turned the rock from red to white, releasing iron and phosphate, possibly creating the black rings. Such reactions may also provide an energy source for microbes.
“Cheyava Falls is the most enigmatic, complex, and potentially important rock that Perseverance has investigated to date,” Ken Farley, Perseverance project scientist and a professor of geochemistry at the California Institute of Technology in Pasadena, said in a statement.
The team also found millimeter-sized crystals of olivine in the same rock. Olivine, previously discovered in another part of the crater by Perseverance, is a mineral that forms from magma. The olivine present in the Cheyava Falls rock could be related to rocks that formed elsewhere in the valley, the team said.
The rover team is grappling with a number of questions as they study the rock and try to figure out what processes might have formed it.
Cheyava Falls may have begun as a mixture of deposited mud and organic compounds that eventually cemented into rock. Later, water may have seeped through cracks in the rock, depositing minerals to create the calcium sulfate veins and leopard spots.
However, it is also possible that the olivine and sulfate were deposited in the rocks by the scorching temperatures on Mars, causing a non-biological chemical reaction that created the leopard spots.
Exploring Mars’ past
Since landing on Mars, Perseverance has crossed Jezero Crater and explored an ancient river delta in search of microfossils of past life, collecting samples along the way that could be returned to Earth on future missions.
More recently, Perseverance explored the northern rim of Neretva Vallis, an ancient river valley that brought water to Jezero crater more than 3 billion years ago, and discovered Cheyava Falls there. The rover landed in the crater in February 2021 to explore the lake’s ancient location.
Geologists on the rover team wanted Perseverance to study rocks that were created or changed by water on Mars in the past, which is why Cheyava Falls was so intriguing to them.
“We designed the route for Perseverance to ensure it goes to areas with the potential for interesting scientific samples,” Nicola Fox, associate administrator for NASA’s Science Mission Directorate, said in a statement. “This trip down the Neretva Valley riverbed paid off because we found something we’d never seen before, which will give our scientists a lot to study.”
The difficult road to finding evidence of life
In April, NASA reported that the original complex, multi-mission design for the program to return Perseverance’s 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 called on NASA centers and industry to develop a new plan that combines innovation with lessons learned from proven technology. NASA leaders hope to return samples to Earth by the 2030s with less complexity, cost and risk than originally planned, and the agency expects 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.
Meanwhile, Perseverance continues its vital exploration work on Mars and will soon begin climbing the rim of Jezero Crater.
“This discovery comes at such a critical time, as NASA rethinks the best way to get these samples back from Mars via Mars Sample Return,” Horgan said. “It shows how important and unique our sample set is, and how much we can learn about the beginnings of life on planets similar to Earth. It also feels very fitting that Jezero provided us with one last surprise before we leave the ancient river and lake sediments of the crater floor behind and climb the rim.”
According to the Perseverance team, sending back the samples is the only way to know if life ever existed on Mars.
“We’ve hit that rock with lasers and X-rays and literally imaged it day and night from almost every conceivable angle,” Farley said. “Scientifically, Perseverance has nothing more to offer. To fully understand what really happened billions of years ago in that Martian river valley at Jezero Crater, we want to bring the Cheyava Falls sample back to Earth so it can be studied with the powerful instruments that are available in laboratories.”
For more CNN news and newsletters, create an account at CNN.com