Life on Mars?
For as long as humanity has walked the Earth, we have gazed into the night sky and questioned our place in the cosmos. At the heart of this search for meaning lies one of the most profound questions: Are we alone in the universe? Civilisations throughout history have passed down tales of powerful beings or visitors from the skies. While modern science has moved beyond myths of gods pushing the sun across the heavens or “little green men” piloting flying saucers, the possibility of life beyond Earth remains an enduring focus of discovery. And now, new evidence from Mars may have brought us closer than ever to answering that question.
On 10 September 2025, NASA’s Acting Administrator announced the results of a paper published in Nature. The study reports that a rock sample from Jezero Crater, collected by the Perseverance rover, contains potential biosignatures - substances or structures that may have a biological origin. The sample, known as Sapphire Canyon, was cored from the “Cheyava Falls” rock (an arrowhead-shaped boulder measuring about 1 m by 0.6 m), located within the Bright Angel formation on the western edge of Jezero Crater. This site was chosen to help scientists reconstruct Mars’s early geology and assess whether it could once have supported life.
Five years into its mission, Perseverance has explored three key terrains in Jezero Crater:
The Crater Floor: ancient igneous rocks formed from cooled magma, providing a baseline record of early Martian volcanic activity.
The Western Fan: a deltaic deposit made of sedimentary rocks derived from ultramafic material (rocks rich in magnesium and iron, typically dark in colour), where a river once flowed into an ancient lake.
The Margin Unit: a layered to massive sequence of igneous rocks. The lower layers formed as minerals settled in a magma chamber, while the overlying massive rocks crystallised from a later, more uniform melt. Orbital instruments revealed strong signatures of olivine (a greenish magnesium-iron silicate common in both volcanic rocks on Earth and meteorites from space) and carbonate (a mineral group that can form when carbon dioxide interacts with water).
Perseverence’s route through the formation
The Bright Angel formation, where Sapphire Canyon was found, lies at a feeder channel into the Western Fan. It consists mainly of fractured and weathered metre-sized blocks of sedimentary rock. Radar measurements from Perseverance’s ground-penetrating instrument (RIMFAX) suggest Bright Angel is stratigraphically younger than the Margin Unit, although its precise relationship to nearby formations remains debated.
In July 2024, Perseverance entered Bright Angel and discovered that its mudstones and sandstones are composed of fine clay and silt grains, typically 30–110 micrometres across, similar to flour-sized particles on Earth. These materials are particularly significant because, on Earth, they are excellent at trapping and preserving organic matter and even microfossils. Moreover, the rocks at Bright Angel are enriched with organic carbon, sulphur, oxidised iron (commonly seen as rust), and phosphorus, all elements that form the chemical foundation for life.
Perseverance’s suite of instruments, including:
PIXL (Planetary Instrument for X-ray Lithochemistry): used to map the elemental composition of rocks at very fine scales;
SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals): capable of detecting organic molecules and minerals by their vibrational “fingerprints”;
WATSON (Wide Angle Topographic Sensor for Operations and eNgineering): a close-up camera paired with SHERLOC;
SuperCam: providing laser-induced breakdown spectroscopy and remote Raman analysis;
Mastcam-Z: stereoscopic cameras with zoom capability;
were used to investigate the Cheyava Falls rock and its companion target, Apollo Temple. Core samples were then drilled and sealed for eventual return to Earth.
The 3 drilled holes, where rock was found to have centimetre scale tan/reddish recessive layers separated by thinner, more resistant, light-toned layers. ‘Steamboat Mountain’ was investigated as a possible transitional lithology between the Bright Angel formation and the Margin Unit.
In the Cheyava Falls rock, Perseverance imaged colourful spots that immediately caught scientists’ attention. In higher-resolution images, these “leopard spots” turned out to be reaction fronts, boundaries where chemical reactions had occurred between minerals and their environment. Spectral analysis revealed two iron-rich minerals within these spots:
Vivianite (Fe₃(PO₄)₂·8H₂O): a hydrated iron phosphate, often blue-green in colour, typically associated with environments rich in decaying organic matter, such as peat bogs or lake sediments on Earth.
Greigite (Fe₃S₄): an iron sulphide mineral, sometimes produced by microbial activity, including bacteria that use sulphur in their metabolism.
Both vivianite and greigite can form through purely chemical (abiotic) processes, such as heating, acidic conditions, or reactions with dissolved organic molecules. However, the Bright Angel rocks show no evidence of exposure to high heat or strong acids. This raises the possibility that organic molecules within the rock could have driven their formation under milder conditions, a process consistent with microbial metabolisms.
Joel Hurowitz, lead author of the study and a scientist at Stony Brook University, explained:
“The combination of chemical compounds we found in the Bright Angel formation could have been a rich source of energy for microbial metabolisms … But just because we saw all these compelling chemical signatures in the data didn’t mean we had a potential biosignature. We needed to analyse what that data could mean.”
Importantly, SHERLOC detected an organic Raman signal, a carbon “G-band” at around 1,600 cm⁻¹, strongest in the Apollo Temple target, weaker in Cheyava Falls, and absent in other nearby samples. This variation suggests that organics are unevenly distributed in the Bright Angel rocks and may be associated with the reaction fronts.
Another intriguing aspect is the relative youth of these rocks. Scientists previously thought that if Mars ever hosted life, evidence would be confined to its oldest rocks, dating back over 3.5 billion years. However, the Bright Angel mudstones are considerably younger, meaning Mars may have been habitable more recently — or for longer periods — than once believed. This raises the possibility that older formations may also contain biosignatures that have so far proven more difficult to detect.
Katie Stack Morgan, Perseverance’s Deputy Project Scientist at NASA’s Jet Propulsion Laboratory, cautioned:
“Astrobiological claims, particularly those related to the potential discovery of past extraterrestrial life, require extraordinary evidence. Getting such a significant finding as a potential biosignature on Mars into a peer-reviewed publication is a crucial step in the scientific process because it ensures the rigour, validity, and significance of our results. And while abiotic explanations for what we see at Bright Angel are less likely given the paper’s findings, we cannot rule them out.”
To evaluate such discoveries, NASA scientists apply the Confidence of Life Detection (CoLD) Scale, a seven-step framework designed to assess the strength of evidence for extraterrestrial life. The scale begins with the mere detection of a possible signal, progresses through steps such as ruling out contamination and non-biological explanations, and culminates in independent confirmation of a biological origin. By this standard, the Bright Angel discovery currently sits in the middle of the scale: tantalising, but not yet definitive.
