Scientists detected a potential biosignature on Mars—an astrobiologist explains the findings

While the Rover of Perseverance crossed an old river valley in the Jezero crater in March in July 2024, it pierced on the surface and extracted a sample of a single striped rock called Cheyava Falls. The instruments of the rover then analyzed the sample, which is called Sapphire Canyon, and studied the surrounding rock.

When scientists began to examine the data, they found two types of iron -rich minerals placed on the rock in a distinctive and spotted model. These two minerals are associated with life on earth. One is around the decomposition of organic matter on earth, while the other is produced by certain microbes.

A team of researchers determined in a study published on September 10, 2025, that the sample contains a potential biosignature – which could suggest the red planet once hosted microbial life.

These minerals may have been formed on the rock when ancient microbes have used chemical reactions to produce energy. But chemical reactions not linked to life can also produce these minerals under certain conditions.

To find out more, the conversation we asked for Amy J. Williams, Astrobiologist at the University of Florida, about hunting for biosigenature on Mars and what is so special in this sample of Canyon Sapphire.

What are biosignatures?

A biosignature is quite characteristic, element, molecule, substance or characteristic which serves as proof of past or present life. It must be something that cannot be produced lifeless. Some examples include fossils, organic molecules derived from a biological process or mineral models which are only formed by microbial activity.

A potential biosignature, namely how the discovery of the sapphire canyon is described, is a substance or a structure which could have a biological origin but requires more data or a more in -depth study before scientists can conclude on the absence or presence of life.

How do scientists determine if something could be a biosignature on Mars?

Biosignatures are available in many different flavors – chemical, physical or structural. Some are rather obvious, such as a fossil of dinosaurs on earth, but most are much more nuanced.

The search for ancient life on earth partially informs the search for biosignatures on Mars. Researchers rely on subtle clues kept in the rock file to answer questions such as microbial lifespan on earth. We are looking for this evidence in environments such as craters and lake beds with high preservation potential, which means those that are likely to preserve biosignatures.

Scientists can apply these techniques looking for life on Mars. This is why perseverance was sent to Jezero Crater. In the ancient past, the crater welcomed a lake nourished with the river, which on earth would represent a habitable environment: the one where life would like to live if it was performing.

This crater was an ideal place to look for an ancient life kept in the rock record on Mars. Astrobiologists then look for chemical, textural and mineral models that resemble processes influenced by life on Earth.

What makes this sample unique and interesting?

The sample of Sapphire Canyon is unique because the Pixl and Sherloc instruments of Perseverance have revealed distinctive textures which have been nicknamed “Leopard spots”. These spots are concentric reaction fronts – places where chemical and physical reactions occur – enriched in vivianitis minerals, which contains iron phosphate, and transfers, which is in iron sulfide.

On earth, vivianitis is often formed in environments with a lot of decaying organic matter, while certain microbes which use sulfate for energy can produce greigitis. The compounds of these two minerals are part of a chemical process called REDOX GRADIERS, which refers to a series of progressive changes compared to the physical space where chemicals can oxidize (losing electrons) or reducing (gain electrons).

An example is to leave your metal bike in the rain. Over time, reduced iron (fe²⁺) will lose an electron and oxide with rust (fe³⁺). This process can occur in a non -biological way, because exposure to water and oxygen leads to the chemical changes that bring your new bike to a rusty bicycle – I suggest not leaving it in the rain.

But certain oxidation and reduction processes are so slow by themselves that the only way they can occur is with living organisms that advance reactions. This process is the number of microbes, such as bacteria, that energy lives. Because these two minerals of the sample of Canyon Sapphire both occur in the redox gradients, scientists predict that microbial life, if it were never present, could have played a role in the reactions that created these mineral signatures.

Now scientists examine the explanations that would not require life to train these features on the sample.

Did scientists expect to find a sample like this?

It was a discovery that we hoped for. However, he was somewhat unexpected in this particular place. This sample has come from some of the youngest sedimentary rocks that the mission has investigated to date. An previous prediction had assumed that signs of ancient life would come from older Martian rock formations.

Finding these characteristics in younger rocks widens the window of time that Mars was potentially habitable and suggests that Mars could have been habitable later in the history of the planet that scientists did not think about it previously, and older rocks could also hold signs of life that are simply more difficult to detect.

What are the next steps to say if the sample indicates signs of past life, or if the signature comes from a non -biological process?

Mineral associations are a potential fingerprint for redox reactions that can occur when microbes advance the reaction, but abiotic processes, such as high temperatures, acid conditions and a bond by organic compounds, could also explain them.

However, Cheyava Falls Rock shows no sign that it has been exposed to the high heat or acidity generally required so that greigite and vivianitis are formed in a non -biological way. However, the only final way to answer this question is to return the sample to earth, where scientists can use advanced laboratory techniques to distinguish the biological origins of non-biologicals.

This article is republished from the conversation under a Creative Commons license. Read the original article.