The trouble with science is that nature is honest. It doesn’t always give you the answers you want. The US space administration NASA has confessed that its priority for future planetary missions to Mars is to look for life. Yet every attempt to find evidence for Martians so far has failed, and it is starting to look as though there might not be any needles in the haystack anyway. Even the report in 1996 of possible ‘fossils’ of Martian bacteria in a meteorite thrown to Earth from the Red Planet now has a tattered reputation. But still Mars teases, exposing glimpses of a wetter past and even perhaps a sporadically watery present.