NASA’s Perseverance rover has collected an unusual, leopard-spotted rock from Mars’ Sapphire Canyon, prompting experiments to determine whether its distinctive markings contain signs of organic molecules.
After Perseverance obtained samples from a highly unusual red mudstone rock bearing white, black-bordered spots reminiscent of a leopard’s coat, researchers at NASA’s Jet Propulsion Laboratory and California Institute of Technology took interest and began preparations for initial study of the sample.
Scientists suspect these distinctive spots may be indicators of organic molecules present on Mars. Perseverance collected the sample from a rock in 2024 as part of its mission to locate the most intriguing finds currently available on the Martian landscape, which NASA plans to bring back to Earth for future study.
O-PTIR
In a new paper in Review of Scientific Instruments, the researchers explored optical photothermal infrared spectroscopy (O-PTIR) as a promising technique for analyzing returned Martian samples. To test the method, they selected a visually similar Earth rock—a piece of basalt with dark spots roughly the same size as those in the Martian sample.
O-PTIR works by targeting a sample with two lasers, each serving a unique purpose. The first laser heats the sample, creating tiny thermal surface vibrations corresponding to the laser’s wavelength. A second laser then captures data on these changes. By comparing the sample’s state before and after heating, researchers can deduce its chemical composition.
A Fortuitous Mars Rover Discovery
Just as the Sapphire Canyon sample was an unexpected Martian find, its Earthly counterpart was also a surprise. Lead author Nicholas Heinz stumbled upon it entirely by chance.
“I was hiking in Arizona, in Sedona, when I saw this rock that just didn’t look like it belonged,” Heinz said. “I put it in my backpack and brought it back to look at.”
The team’s goal was to determine whether O-PTIR could distinguish between the main body of the rock and the dark spots, identifying the unique substances responsible for the discoloration. The results showed that O-PTIR excelled at this task, thanks to its high spatial resolution. Another advantage is its speed—it can produce initial results in minutes, allowing scientists to quickly decide whether to follow up with more sensitive but time-intensive techniques if organic compounds are suspected.
“I hope this capability will be considered for any future material returned from Mars, an asteroid, or any other planetary surface,” said Heinz.
Exploration Missions
JPL is currently the only facility offering the O-PTIR technique, which it previously used in 2024 to confirm the cleanliness of NASA’s Europa Clipper spacecraft before launch. Europa Clipper is on track to reach Jupiter’s icy moon Europa in April 2030, where it will conduct 49 flybys in search of signs of subsurface habitability.
Looking ahead to Mars, Heinz says the team sees additional applications for O-PTIR in analyzing returned samples and for broader geological research. They are currently testing the technique on Earthly algal microfossils used as analogs during Mars rover development. While Perseverance continues collecting carefully selected samples, the Mars Sample Return mission—planned as a joint effort between NASA and the European Space Agency—remains in development.
The paper, “Application of Optical Photothermal Infrared Spectroscopy (O-PTIR) for Future Returned Mars Samples,” appeared in Review of Scientific Instruments on August 12, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.