Mars rover spots molecules that may have been left behind by Martians (but other, less exciting explanations are possible)

Perseverance has found promising organic molecules in Jezero Crater, which are also considered “the building blocks of life.” But whether they were actually left behind by Martian microbes remains debatable.

It’s been about two years since the Mars Perseverance rover landed in Jezero Crater on Mars. Since then, the Mars rover has been carefully scanning the crater, looking for signs of (ancient) life. And the thief may have just found this. For example, Perseverance appears to have uncovered evidence for different types of organic molecules, the researchers say.

Organic molecules
The organic molecules found are a class of carbon-based molecules. “They correspond to molecules that contain carbon and are the building blocks of life as we know it,” says team member Ashley Murphy. “This is one of the first times we’ve found potential organic material in Jezero Crater.” The discovery is therefore quite exciting. Because the organic molecules discovered may have been left behind by ancient microbial life! Although this does not necessarily have to be the case.

building blocks for life
Organic molecules are mainly composed of carbon and usually contain hydrogen and oxygen atoms. They may also contain other elements such as nitrogen, phosphorus and sulfur. The discovery of such organic molecules is important because some of these compounds are the building blocks of life. The presence of these specific molecules is considered a potential biosignature – a substance or structure that could be evidence of past life. Yet scientists are wary. Some organic molecules can also be created by chemical processes, without the presence of life.

Not of biological origin
“Not all organic molecules have a biological origin,” Murphy explains. “That is why it is important to study the relationship between minerals and organic substances. All that we know of life on Earth is limited to what is preserved in rock and minerals. On Earth, biosignatures are found in certain minerals, and some minerals are better at preserving organic matter than others.

Mars and Earth
This means that researchers often use Earth as an example to find out what could have happened on Mars. “Mars may have had an early geological history similar to Earth’s, so we are using our knowledge of life as we know it on Earth to search for possible evidence of past life on Mars,” said Murphy. “Mapping organic matter provides a better understanding of the Martian carbon cycle. We can then determine if it is similar or different from that of the Earth. It will also tell us more about the likelihood that Mars supported life.

SHERLOC
Organic molecules were revealed using Perseverance’s SHERLOC instrument. SHERLOC – an abbreviation for Scanning habitable environments with Raman and luminescence for organics and chemicals – uses an ultraviolet laser to identify minerals in the rock. Additionally, the instrument is equipped with cameras and spectrometers to search for organic and mineral matter that may be signs of past microbial life. “The SHERLOC instrument, mounted on Perseverance’s robotic arm, allows us to assess potential biosignatures,” says Murphy.

Máaz and Séitah
The researchers used the SHERLOC instrument to take a closer look at two Martian rock formations, Máaz and Séítah. Perseverance drilled small holes in the rock for this purpose. And the team found traces of organic molecules in all ten locations. “Potential organics are in multiple layers,” Murphy says. “This may indicate that Mars once had distinct surface processes and relatively complex organic geochemistry. On Earth, this is associated with certain habitable environments where signs of ancient life can be preserved.

Other finds
This is not the first time that organic matter has been discovered on Mars. Perseverance and the Curiosity rover have encountered this before. “The newly discovered molecules are similar to those previously found in Gale Crater and in several meteorites,” Murphy said. “The detection of various organic materials in two ancient lakes (the Gale and Jezero craters) is important for our understanding of the magnitude and diversity of surface processes and their connection to planetary habitability.”

Origin
But again, the discovery is by no means confirmation that life ever existed on Mars. Organic molecules can form in a variety of ways, including through non-biological processes such as water-rock interactions, deposition by dust or interplanetary meteors, or by synthesis with volcanic materials. At present, it is not yet known what is the exact origin of the organic molecules that have surfaced.

Although the organics are not proof of past life, the discovery is still exciting because it shows that Mars has the building blocks of life. The samples will now need to be brought back to Earth and examined in more detail before any firm conclusions can be drawn. We will therefore have to be patient for some time before we can determine once and for all whether there is (or was) life on Mars.