Illustration by Claudio Munoz

AS LONG as people have looked up at the night sky, they have wondered whether humanity is alone in the universe. Of places close enough for people to visit, Mars is the only one that anybody seriously thinks might support life. The recent confirmation of a five-year-old finding that there is methane in the Martian atmosphere has therefore excited the hopes of exobiologists—particularly as the sources of three large plumes of the gas now seem to have been located. These sources are probably geological but they might, just, prove to be biological.

The possibility of life on Mars is too thrilling for mankind to ignore. But how should we explore such questions—with men, or machines? Since America is the biggest spender in space, its approach will heavily influence the world's. George Bush's administration strongly supported manned exploration, but the new administration is likely to have different priorities—and so it should.

Bug-eyed monsters

Michael Griffin, the boss of American's National Aeronautics and Space Administration (NASA), a physicist and aerospace engineer who supported Mr Bush's plan to return to the moon and then push on to Mars, has gone. Mr Obama's transition team had already been asking difficult questions of NASA, in particular about the cost of scrapping parts of the successor to the ageing and obsolete space shuttles that now form America's manned space programme. That successor system is also designed to return humans to the moon by 2020, as a stepping stone to visiting Mars. Meanwhile, Mr Obama's administration is wondering about spending more money on lots of new satellites designed to look down at the Earth, rather than outward into space.

These are sensible priorities. In space travel, as in politics, domestic policy should usually trump grandiose foreign adventures. Moreover, cash is short and space travel costly. Yet it would be a shame if man were to give up exploring celestial bodies, especially if there is a possibility of meeting life forms—even ones as lowly as microbes—as a result.

Luckily, technology means that man can explore both the moon and Mars more fully without going there himself. Robots are better and cheaper than they have ever been. They can work tirelessly for years, beaming back data and images, and returning samples to Earth. They can also be made sterile, which germ-infested humans, who risk spreading disease around the solar system, cannot.

Humanity, some will argue, is driven by a yearning to boldly go to places far beyond its crowded corner of the universe. If so, private efforts will surely carry people into space (though whether they should be allowed to, given the risk of contaminating distant ecosystems, is worth considering). In the meantime, Mr Obama's promise in his inauguration speech to “restore science to its rightful place” sounds like good news for the sort of curiosity-driven research that will allow us to find out whether those plumes of gas are signs of life.