A rock sample taken from the Jezero crater contains potential "biosignature", molecules that on Earth are often associated with forms of microbial life

NASA (the American space agency) announced today a discovery that could rewrite the history of Martian exploration. The rover Perseverance, operating on the Red Planet since 2021, has identified in a rock sample collected last year what scientists call "potential biosignatures". These are molecules and structures that could have a biological origin, but which require further analyses to confirm the presence of past or present life.

The "leopard spots" and their implications

The sample, named "Sapphire Canyon", was collected from the rock "Cheyava Falls", located in the "Bright Angel" formation inside Jezero Crater, an ancient riverbed now dried out. The discovery was published in a prestigious scientific journal and has already generated a wave of excitement in the scientific community. The rover's onboard instruments, PIXL and SHERLOC, detected strange formations on the rock called "leopard spots". These spots, observed at high resolution, are composed of a combination of iron-rich minerals: vivianite (hydrated iron phosphate) and greigite (iron sulfide). On Earth, vivianite is often found in environments such as peat bogs and sediments rich in decomposing organic matter, while greigite can be produced by specific microorganisms. The simultaneous presence of these minerals in a carbon-rich sedimentary formation containing sulfur and phosphorus led scientists to suggest they could be the result of electron-transfer reactions, a fundamental chemical process used by many organisms to produce energy.

An unexpected discovery that expands the boundaries of Martian habitability

The excitement about the discovery is palpable among mission leaders. Sean Duffy, NASA's acting administrator, stated that this is "the closest we have come to finding life on Mars". Although caution is advisable, as emphasized by the Perseverance project scientist, Katie Stack Morgan, the significance of the finding cannot be understated. "Astrobiological claims require extraordinary evidence", said Stack Morgan, "and publication in a peer‑reviewed scientific journal is a crucial step to ensure the rigor and validity of our results".

The discovery was particularly surprising because it concerns some of the youngest sedimentary rocks analyzed by the mission so far. This suggests that Mars may have remained habitable for a longer period than previously thought, or during a more recent epoch of its geological history. Pending future missions that will return Martian rock samples to Earth for more thorough analysis, the international scientific community will now have access to the rover's data to confirm or refute the biological origin of these intriguing "biosignatures".

In the video below from NASA, an animation shows the disappearance of water over time in the Neretva river valley on Mars, where the Perseverance Mars rover collects the rock sample named "Sapphire Canyon" from a rock called "Cheyava Falls", found in the "Bright Angel" formation.