University of Tennessee, Knoxville part of Mars team finding possible sign of life

A professor from the University of Tennessee, Knoxville, is part of the scientific team that has identified a potential sign of early life on Mars.

Linda Kah, the Kenneth R. Walker Professor in UT's Department of Earth, Environmental, and Planetary Sciences, is a co-author on the peer-reviewed study published in the journal Nature on September 10, 2025.

"The identification of a potential biosignature on the Red Planet is a groundbreaking discovery, and one that will advance our understanding of Mars," said acting NASA Administrator Sean Duffy during a news conference.

While NASA and affiliated researchers are celebrating the closest evidence yet of potential life on another planet, they also are cautioning that there may be other explanations for what they have seen amid some of the oldest rocks in the solar system, on the edge of what was an ancient river valley.

"We have not found evidence for life; we have found intriguing data that, if collected on Earth, would likely be ascribed to biological processes," Kah said. "But we cannot claim that we have found life without extensive additional testing—much of which will have to wait until samples are returned to Earth."

Leopard Spots on Mars

Kah is a co-investigator on the SHERLOC-WATSON instrument suite on the Perseverance Mars Rover. SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) detects organic molecules.

The WATSON instrument, where Kah plays her largest role, is a wide-angle camera on the rover arm designed to capture highly detailed images of the rocks, about 0.015 millimeter per pixel.

As the rover moved into an area on Mars called Bright Angel last summer, it showed rocks that were very different from previous areas. Amid fine sediment that formed the rocks are areas described as "leopard spots," patterns that indicate a point where chemical and physical reactions occurred.

"For any of us on the team who do a lot of geological field work here on Earth, the combination of a rock type and these curious spots were very reminiscent of features we see in flood plains, muddy shorelines, and soils, so it was very exciting," Kah said.

Amid the clay and silt, the sedimentary rocks include organic carbon, sulfur, oxidized iron, and phosphorus. Researchers have found organic material on Mars before, but what's different in the new images are the spots, which on Earth are commonly produced when microbes feed on organic matter.

UT Student Roles

Kah spent nearly four years on the primary leadership team for the Perseverance rover mission. "I recently chose to refocus my commitment to a more hands-on role as a scientist—my true love—which has the bonus of giving me more time to spend with my own students here at UT," she said.

Many UT students have worked with Kah on Mars research.

"Before Perseverance landed, several undergraduates aided the team in their efforts to create detailed maps of the landing site," she said. "I currently have four Ph.D. students involved in this mission in some capacity, as well as on the activities of the Curiosity rover."

The graduate students are involved in research that includes interpreting WATSON images, understanding water flow into Jezero Crater, calculating rock strength from data collected when the rover drills samples, and exploring features on Earth to better understand the martian data.

Last month several UT graduate students and Kah traveled to the Stillwater Complex in the Beartooth Mountains of Montana. "We were collecting potential analog materials to other rocks that Perseverance has seen in Jezero Crater," she said. "Using these materials, we can explore the full range of what information can, and cannot, be gained from instruments on Mars."

UT undergraduate students also are looking at a variety of data from Mars.

Currently the Perseverance rover isn't expected to send samples back to Earth for more than seven years. "By that point, I expect that I will be on the verge of retirement," Kah said. "My job is, therefore, to make sure that any samples that might get returned have the best scientific context that we are able to collect while on Mars. It is the undergraduate and graduate students of today who will be proposing to work on these samples once they return home."

Kah's main research is focused on understanding how Earth's atmosphere changed to include oxygen and how that drove chemical change in the oceans and the evolution of life. "Working on Mars is very different: You cannot just pick up a rock, and you cannot believe that your assumptions built on Earth are the same," she said. "It provides a lot of additional challenges."

More information:
www.nature.com/articles/s41586-025-09413-0

Provided by University of Tennessee at Knoxville