Nasa’s Curiosity rover has trundled across the beds of dried-up lakes on Mars, and it has been fairly clear that Mars had surface water bodies in the past. This is not evidence for the prior existence of little green men, but extinct, little green microbes cannot be ruled out. Now, a radar instrument on the European Space Agency’s Mars Express orbiter has detected a sizeable body of liquid water under the ice cap of the south pole of Mars, which could be a game-changer in the search for extraterrestrial life. But excited scientists are neglecting to add the operative word: “Someday”.
Detecting water on other planets is a foundational project of astrobiology. It is the starting point in the search for alien life, which has been one of humanity’s obsessions. Apart from the gigantic scientific consequences, the discovery of life elsewhere would also have profound philosophical, religious and political effects.
But the drama would be the late, late show. The liquid water on Mars has been found 1.5 km under the ice, and the only way to test it for the presence of life would be to drill that deep. That implies a separate mission with a robot capable of sinking a probe and testing the waters. Despite the hopeful rhetoric from the private space industry, it is financially prohibitive to send a manned mission now. And, as science fiction has speculated, life elsewhere could be so alien as to be unrecognisable by humans. Stanislaw Lem wrote of a sentient ocean. A living lake? Well, why not?