Via NASA

Julia Azzouz

Creative Writing Editor

Launched in 2020, the NASA (National Aeronautics and Space Administration) Perseverance rover has been tasked with collecting samples from Mars to send back to Earth with the aim of detecting microbial life on the planet’s surface. In 2024, Perseverance discovered a rock unlike any other observed, pockmarked with a cluster of small, darkened rings that scientists likened to “leopard spots” and “poppy seeds.” The “Cheyava Falls” rock, named after a Grand Canyon waterfall, was extracted by the rover into sample 25, also known as “Sapphire Canyon.” This core is considered one of the mission’s most promising specimens from the Red Planet.

On September 10th, 2025, a peer-reviewed paper titled “Redox-driven mineral and organic associations in Jezero Crater, Mars” was published by NASA planetary scientists, astrobiologists, and geologists. They concluded that the Cheyava Falls sample offers some of the most compelling evidence to date for potential biosignatures on Mars, while emphasizing that definitive proof of past life remains unconfirmed. Although no conclusive claims can yet be made, many alternative hypotheses have been carefully evaluated and found less likely, with biosignatures remaining the leading explanation. 

Although the sample is not expected to be returned to Earth for many years, Perseverance is equipped with analytical tools that can probe its findings from Mars until laboratory work is made possible. The rover uses PIXL (Planetary Instrument for X-Ray Lithochemistry), an x-ray fluorescence spectrometer, to identify the elemental composition of Martian surface materials on a tiny scale. Perseverance also uses SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals), a device mounted on the rover’s arm that uses cameras, spectrometers, and a laser to detect organic particles and certain minerals. SHERLOC is aided by the aptly-named WATSON (Wide Angle Topographic Sensor for Operations and eNgineering), a colour camera that takes close-up images of rock grains and textures. 

For the Perseverance mission, scientists at NASA strategically selected the rover’s landing location. Just north of the Martian equator, the Jezero Crater was chosen because it once held a lake and delta system that thrived billions of years ago, making it a prime candidate for preserving ancient life. Thanks to PIXL and SHERLOC, Perseverance was able to analyse various samples from the crater, including Cheyava Falls’ leopard spots and poppy seeds where it detected carbon-based compounds i.e. organic carbon. The rover also identified traces of iron, phosphorus, sulfur, and most notably, vivianite (hydrated iron phosphate) and greigite (iron sulfide), which on Earth are associated with biological processes, including the decay of animal and plant matter. While microbial life is one possible explanation, scientists continue to explore alternatives.

One hypothesis posits that similar results could arise if the rock were subjected to prolonged heating. The presence of carbon-based compounds could be explained by high temperature chemistry in the Martian soil without the involvement of living organisms. Olivine, found on Cheyava Falls’ surface, is a mineral that primarily forms through the crystallization of magma, supporting such a theory. However, vivianite typically forms under low-temperature conditions and cannot withstand extreme heat. The Jezero Crater ranges from approximately -22ºC to -83ºC, and no current data suggests that the high temperatures required for such chemical reactions can be naturally generated on Mars. The presence of vivianite in the sample thus makes high-temperature chemical formation an unlikely explanation.

Scientists also hypothesize that acidic water interactions could have formed the same minerals. Acid can dissolve certain rock types like carbonates and silicates which can change their redox state (reduction-oxidation reaction) and alter the rock’s chemical properties. If acid water flowed through the rock, a chemical reaction could have generated vivianite and greigite through abiotic means. However, for this to be consistent, olivine would have to have formed after the acid interaction because olivine dissolves in acid. Since olivine crystallizes from magma and intense heat would destroy vivianite, it is unlikely olivine formed after acid flow, and it is also improbable it formed before acid flow because it would have dissolved during acid exposure.

Therefore,

“the prevailing hypothesis— though not established as a scientific theory— involves organic material.”

In this scenario, the microbes act as a catalyst for mineral formation, meaning that they accelerate the chemical reaction without themselves being consumed, unlike heat or acid. Microbes use minerals like iron, sulfur, and phosphorus to obtain energy, releasing or transforming these elements. This metabolic process can cause minerals like vivianite or greigite to form in specific spots with low oxygen and high nutrients like carbon, nitrogen, phosphorus, sulfur, and other trace elements like magnesium, calcium, and potassium.

During NASA’s press release, NASA’s current acting administrator, Sean Duffy, stated that Cheyava Falls could “very well be the clearest sign of life that we have ever found on Mars,” noting that scientists “couldn’t find another explanation.” While confidence in the presence of biosignatures grows, researchers remain cautious. No definitive claims can be made until the samples are returned to Earth and thoroughly analyzed in laboratory conditions. As former NASA administrator Bill Nelson explained in a 2025 CNN interview, the Mars Sample Return program is undergoing major redesign to “reduce complexity, cost, and mission duration.” Until then, the scientific community continues to weigh the evidence carefully, remaining mindful of Carl Sagan’s dictum: “Extraordinary claims require extraordinary evidence.”