“This very well could be the clearest sign of life that we’ve ever found on Mars,” said acting Nasa administrator Sean Duffy at a press conference on Wednesday.

NASA’s Perseverance rover has spotted intriguing chemical fingerprints in Martian rock that could hint at ancient microbial life.

Professor Sanjeev Gupta, a planetary scientist from Imperial College London, said: "We've not had something like this before, so I think that's the big deal.