As learned just today, NASA's Perseverance rover has found complex carbon molecules in rocks on Mars's surface that could hypothetically be linked to microbial life. The organic carbon was detected in shale rocks (fine-grained sedimentary rocks) at Bright Angel, along an also ancient riverbed that once carried water into Jezero Crater.
Although the finding is naturally intriguing, it can't be understood as proof of life. Macromolecular carbon can in fact come from biological sources, but scientist explain that it can also be produced by geological processes or even delivered by meteorites. So far, no one can say whether it came from ancient Martian microbes.
From this point, the key answers to those scientists' questions will require bringing Mars samples back to Earth, as the rover can identify promising rocks, but it can't confirm if the carbon is biological by itself. NASA is now planning a new mission to return samples for the next decade (2030s), while China wants to fetch Martian samples in 2031 already.
Source: elDiario.