Rock discovery contains ‘clearest sign’ yet of ancient life on Mars, NASA says

By Ashley Strickland, CNN

(CNN) — Scientists believe intriguing leopard spots on a rock sampled by the Perseverance rover on Mars last year may have potentially been made by ancient life, NASA announced Wednesday. The team has also published a peer-reviewed paper in the journal Nature about the new analysis, though they say further study is needed.

“After a year of review, they have come back and they said, listen, we can’t find another explanation,” said Acting NASA Administrator Sean Duffy. “So this very well could be the clearest sign of life that we’ve ever found on Mars, which is incredibly exciting.”

The sample, called Sapphire Canyon, was collected by the Perseverance rover from rocky outcrops on the edges of the Neretva Vallis river valley, a region sculpted by water that once flowed into Jezero Crater more than 3 billion years ago. The rover landed within the crater to explore the ancient lake site in February 2021, seeking rocks created or modified by water on Mars in the past.

Perseverance drilled the Sapphire Canyon sample from an arrowhead-shaped rock called Cheyava Falls in July 2024.

Although the sample is safely ensconced in a tube millions of miles away on Mars, scientists have remained intrigued by the rock because of its potential to reveal whether microscopic life ever existed on Mars.

“The discovery of a potential biosignature, or a feature or signature that could be consistent with biological processes, but that requires further work and study to confirm a biological origin is something that we’re sharing with you all today that grows from years of hard work, dedication and collaboration between over 1,000 scientists and engineers here at the (NASA) Jet Propulsion Laboratory and our partner institutions around the country and internationally,” said Katie Stack Morgan, Perseverance project scientist at JPL, during a news conference Wednesday.

Shortly after the rock was found, members of the Perseverance science team said it was exactly the type of rock they were hoping to find. NASA initially shared the Cheyava Falls rock discovery at the end of July 2024.

The new announcement Wednesday is the result of a long, peer-reviewed research process and the collection of more data, said lead study author Joel Hurowitz, a planetary scientist at Stony Brook University in New York.

Peer review and publication are crucial steps in the scientific process that allow NASA to make the mission data and the science team’s interpretation of that data available to the broader science community for further study, said Lindsay Hays, senior scientist for Mars Exploration at NASA’s Planetary Science Division.

“Hopefully, eventually this will be followed by the delivery of these samples back to Earth where they could be studied in terrestrial labs,” Hays added.

Perseverance rover surveyed the river valley after finding the sample to better understand the environment where the rocks were deposited and determine how the leopard spots may have formed, Hurowitz said.

Understanding exactly how those spots came to be — whether through geochemical processes that don’t require life, or due to the presence of microbial life — is a crucial step in determining whether the rock contains evidence of a potential biosignature.

“Today, we are really showing you how we are kind of one step closer to answering humanity’s, one of their most profound questions, and that is, are we truly alone in the universe?” said Nicky Fox, associate administrator for NASA’s Science Mission Directorate.

Investigating Cheyava Falls

More than 3.5 billion years ago, Neretva Vallis would have been filled with rushing rivers carrying mud, sand and gravel into the lake, Stack Morgan said.

“Inside the crater, this kind of energetic setting was probably punctuated by periods of calm when water would have backed up, creating a relatively low energy lake environment,” she added.

When the water eventually dried up, it left behind the rocky outcrop where Cheyava Valls was found, called Bright Angel, preserving a record of a “potential habitable environment” on Mars, Stack Morgan said.

“These really ancient rocks provide us the window into a period of time that’s not particularly well represented on our own planet Earth, but it’s a time when life was emergent on Earth, and could have been on Mars as well,” she added.

Cheyava Falls, named for one of the Grand Canyon’s waterfalls, showcased small black spots nicknamed “poppy seeds” by Perseverance’s science team, as well as larger markings dubbed leopard spots.

“These textural features told us that something really interesting had happened in these rocks, some chemical reactions occurred at the time they were being deposited,” Hurowitz said.

The rover’s SHERLOC instrument, or Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals, also detected organic compounds in the rock.

The SHERLOC results were a “smoking gun indicator for the presence of organic matter in this mud,” Hurowitz said. Organic compounds were also found in a couple of other locations in the Bright Angel formation.

“This tells us that we had a rusty red mud that was deposited in the presence of organic matter,” Hurowitz said.

On Earth, these carbon-based molecules are the building blocks of life. The mottling on the rock could indicate that ancient chemical reactions occurring within it once supported microbial organisms.

White veins of calcium sulfate present clear evidence that water — crucial for life — once ran through the rock. 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.

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’ signature red hue. The leopard spotting may have occurred when chemical reactions with hematite turned the rock from red to white, which can release iron and phosphate and potentially cause the black rings to form. Such reactions can also provide an energy source for microbes.

The features are likely due to the presence of ferrous iron phosphate and iron sulfide, or the minerals vivianite and greigite, according to the researchers. Typically, these minerals form in environments with a low temperature and the presence of water.

“On Earth, things like these sometimes form in sediments where microbes are eating organic matter and ‘breathing’ rust and sulfate,” said study coauthor Dr. Michael Tice, a geobiologist and astrobiologist in the department of geology and geophysics at Texas A&M University, in a statement. “Their presence on Mars raises the question: could similar processes have occurred there?”

Getting proof of life

In the study, the authors explore two potential scenarios for how the rock features formed: due to the presence of life or without it.

While it’s possible that some of the features could be produced strictly geochemically due to reactions between organic matter and iron, that process usually only works at relatively high temperatures — something the team does not see evidence of, Tice said.

“All the ways we have of examining these rocks on the rover suggest that they were never heated in a way that could produce the leopard spots and poppy seeds,” Tice explained. “If that’s the case, we have to seriously consider the possibility that they were made by creatures like bacteria living in the mud in a Martian lake more than three billion years ago.”

Cheyava Falls may have begun as a mixture of deposited mud and organic compounds that eventually cemented to become rock, according to the research. Later on, water may have penetrated through cracks in the rock, depositing minerals to create the calcium sulfate veins and leopard spots.

“What’s exciting about these finds, this sort of combination of mud and organic matter that has reacted to produce these minerals and these textures, is that when we see features like this are often the byproduct of microbial metabolisms that are consuming organic matter and making these minerals as a result of those reactions,” Hurowitz said.

Hurowitz also acknowledged that there are nonbiological ways to create features like the leopard spots.

“What we need to do from here is to continue to do additional research in laboratory settings here on Earth, and ultimately bring the sample from this rock back home to Earth, so that we can make the final determination for what process actually gave rise to these fantastic textures,” he said.

Scientists are still in the process of analyzing the geologic context of the sample, but the new paper represents an overview of how they currently understand the Cheyava Falls rock, Stack Morgan said. More papers are expected over the next year or so.

“While we were exploring the Bright Angel area, we basically threw the entire rover science payload at this rock, and so we’re pretty close to the limits of what the rover can do on the surface in terms of making progress on that particular question,” Stack Morgan said.

Since landing on Mars, Perseverance has crossed Jezero Crater and explored an ancient river delta in search of microfossils of past life. The rover has been collecting samples along the way that were intended to be returned to Earth by future missions.

But it’s currently unclear how NASA would return the samples to Earth as the agency grapples with the White House’s proposal to slash NASA’s science budget by as much as half.

“We’re looking at how we get the sample back, or other samples back,” Duffy said. “What we’re going to do is look at our budgets, we look at our timing, and you know, how do we spend money better, and you know, what technology do we have to get samples back more quickly? And so that’s a current analysis that’s happening right now.”

To ultimately answer the question of whether life has ever existed on the red planet, returning the samples is necessary, scientists say.

“Bringing this sample back to Earth would allow us to analyze it with instruments far more sensitive than anything we can send to Mars,” Tice said. “What’s fascinating is how life may have been making use of some of the same processes on Earth and Mars at around the same time. It’s a special and spectacular thing to be able to see them like this on another planet.”

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