NASA said its Curiosity rover, looking for signs of life on Mars’ Gale Crater, has found intriguing carbon signatures. While this is no definite suggestion that Curiosity has found proof of ancient microbial life, it does, however, suggest its possibility. The rover has been collecting powdered rock samples on the Red Planet’s surface. When scientists analysed them, they found several of the samples were rich in a type of carbon that is associated with biological processes on Earth, the space agency said. Carbon is a key element on Earth and could hold vital information about the Martian environment.

Scientists do not want to get ahead of themselves and are maintaining that they are yet to find conclusive supporting evidence of life — such as sedimentary rock formations produced by ancient bacteria or diversity of complex organic molecules formed by life on Mars. They also caution that the two planets are very different and Earth examples should not be extrapolated to Mars.

Curiosity scientists published their findings in the Proceedings of the National Academy of Sciences journal on January 18. In this paper, the scientists have offered several explanations for the “unusual carbon signals” they detected. In a blog post, NASA said the biological explanation in the paper is inspired by life on Earth. Two other hypotheses offer non-biological explanations. One of them says the carbon signature could have been a result of interaction between ultraviolet light and carbon dioxide gas. The other suggests that the carbon could have been left behind from a rare event hundreds of millions of years ago when the solar system passed through a giant molecular cloud.

“We’re finding things on Mars that are tantalizingly interesting, but we would really need more evidence to say we’ve identified life,” said Paul Mahaffy, who served as a principal investigator of a chemistry lab aboard Curiosity until his retirement in December 2021. “So we’re looking at what else could have caused the carbon signature we’re seeing, if not life.”