On 20 July 1976, a three-legged spacecraft the size of a small car touched down on a rust-coloured plain and changed everything. Viking 1 had arrived on Mars. NASA's chief scientist Gerald Soffen studied the data, found no wriggling microbes, and declared four famous words: "No bodies, no life." The world moved on.

Or did it? Fifty years later, chemist Steven Benner — a former professor at Harvard — is making a provocative claim in his new book, *Meet the Neighbours*. He argues that Viking's instruments were not wrong about what they detected. They were wrong about what it *meant*.

The experiments, he suggests, may have encountered chemical signatures that were actually consistent with living organisms — and the scientists simply did not recognise them for what they were. For half a century, he contends, the evidence for Martian life has been sitting in the archives, quietly waiting. The stakes could hardly be higher. Viking 1 and its successor spent six years mapping 97% of the Martian surface and transmitting more than 50,000 images back to Earth.

That data still shapes how scientists think about space today.