According to news on September 11th, NASA's Perseverance rover has been exploring an area on Mars called Jezero Crater since February 2021. The crater is a large depression believed to have once been a lake. Jezero Crater is considered one of the most promising sites on the Red Planet for finding evidence of ancient life (at least life as we know it today), and now there's new progress in its exploration efforts.

On September 10th, researchers released a study detailing how Perseverance discovered highly interesting minerals in a clay-rich mudstone area called Neretva Valley on the western rim of Jezero Crater.

"When we see these types of signatures in sediments on Earth, these minerals are often byproducts of microbial metabolism consuming organic matter," Joel Hurowitz, a planetary scientist at Stony Brook University in New York and lead author of the new study, said at a NASA press conference on Wednesday (September 10).

So, does this mean we've finally found evidence of extraterrestrial life? The answer is no. The study authors emphasize that further analysis is needed to determine the true origin of these minerals and whether they are indicators of life (also known as "biomarkers") or the products of other inorganic processes.

"I want to remind everyone that what we're describing is only a potential biomarker," Lindsay Hayes, senior scientist for Mars Exploration in the Planetary Science Division at NASA Headquarters, said at the press conference. "It could be a signature element, molecule, substance, or form of biological origin, but more data and further study are needed before we can definitively say whether life existed."

Regardless, this discovery does suggest that remarkably complex reactions occurred on Mars (whether organic-related or not), adding another dimension to the exploration of a planet that humans have been trying to decipher since the dawn of astronomy.

Specifically, the samples collected by Perseverance, suspected of containing these important minerals, came from the Bright Angel formation on the northern edge of the Neretva Valley. Within this formation, a rock called "Cheava Falls" has garnered significant attention from researchers.

When the "Cheava Falls" rock was first unveiled to the public, it made headlines worldwide, with scientists raving about its unique speckled features. These millimeter-sized specks are surrounded by dark rings. Analysis by Perseverance's onboard sensors revealed that these rings contain iron and phosphate. On Earth, both substances are likely produced by chemical processes driven by microorganisms.

"These spots were a big surprise," said David Flannery, an astrobiologist at Queensland University of Technology in Australia and a member of the Perseverance science team. "On Earth, these types of features in rocks are often associated with the fossil record of subsurface microorganisms."

Hurowitz explained, "We observed these fascinating features within layers of fine-grained, rust-red mudstone in this rock. These structural features suggest that something very interesting happened during the formation of these rocks, a series of chemical reactions that occurred during their deposition."

Perseverance's next mission will be to conduct a more detailed examination of the "Chiava Falls" rock (and other samples associated with the Bright Angel Formation). On July 21, 2024, the rover even drilled into the "Chiava Falls" rock and collected a sample. This was Perseverance's 25th sample, named "Sapphire Canyon."

"I'd describe the Sapphire Canyon sample as 'mysterious,'" Morgan Cable, a research scientist on the Perseverance rover, said in a NASA video released on April 10 about the core sample. "We see some signatures of chemical reactions that could be associated with organic matter, but what does that mean? Was it life involved, or was it something completely unrelated?"

Until now, the story of exploration largely stopped at this stage.

Now, new research appears to have added crucial information to this quest—a detailed analysis of a cluster of Bright Angel Formation samples. Researchers have indeed found that this outcrop could be a crucial clue in the search for evidence of extraterrestrial life. According to a statement about the findings, the team "identified tiny nodules and spots rich in iron phosphate and iron sulfide. These signatures are associated with organic carbon and appear to have formed at low temperatures after sediment deposition."

The key finding appears to be the confirmation that specific "redox reactions" likely occurred to form these minerals. Redox reactions are chemical reactions in which electrons are transferred between two substances, with one being oxidized and the other reduced.

“This organic carbon appears to have participated in post-sedimentary redox reactions, and it is these reactions that produced the iron phosphate and iron sulfide minerals we observed,” the study authors wrote.

Janice Bishop of the Search SETI Institute in Mountain View, California, and Mario Parente of the University of Massachusetts Amherst co-authored a News & Views article published alongside the research. The article states: "The exciting discovery of reduced iron phosphate and iron sulfide associated with organic compounds in the clay-rich mudstones of Jezero Crater suggests that these organic compounds may be involved in specific redox reactions."

The article further adds: "On Earth, microorganisms often interact with minerals. Researchers have observed microorganisms in cold, oxygen-free Antarctic lakes converting sulfates (containing oxidized sulfur atoms) into sulfides (containing reduced sulfur atoms). There is no evidence of microbial life on Mars today, but if ancient Martian microorganisms existed, they might also have reduced sulfate minerals to sulfides in lake environments like Jezero Crater."

Several other findings presented in the team's paper further support the possibility of biomarkers in the Bright Angel Formation on Mars. For example, new findings suggest that green spots in clay mud outcrops of the formation may contain violet iron. The News & Views authors suggest that violet iron helps reveal specific types of redox reactions that may have occurred on Mars.

Ultimately, however, one crucial issue remains: to confirm whether the sample tubes collected by Perseverance contain evidence of Martian life, they must be returned to Earth. Unfortunately, budget constraints, shifts in NASA's mission priorities since the Trump administration, and the inherent complexity of the mission's execution have stalled NASA's Mars sample return program.

Nevertheless, scientists repeatedly emphasize the limitations of analyzing tiny rock samples in the vacuum of space 140 million miles from Mars.

"We are nearing the limits of the rover's ability to explore the Martian surface, a capability that was designed from the outset," Katie Stack Morgan, Perseverance project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, said at the launch event. "Perseverance's payload configuration has always been centered around a Mars sample return mission; our vision is to use the payload to initially confirm the presence of potential biomarkers, with further analysis to be performed by instruments in Earth-based laboratories."

"Laboratory analysis of samples returned from Mars could also shed light on the possibility of prebiotic and even biochemical processes occurring on other planets," the News & Views authors wrote.