A young discipline holds promise yet.
In the 1960s, the evolutionary theorist George Gaylord Simpson rubbished the then-nascent science of exobiology, which concerned itself with life on places other than Earth, as a science without a subject.
Now the science descended from exobiology, astrobiology, is heading towards its tenth birthday. But as hundreds of its practitioners assemble this week in Washington for their annual AbSciCon meeting, the same criticism is being heard once more. And simpsonian scepticism that astrobiology has any useful data or insights to offer makes it easy to cut budgets for the discipline, as NASA has done (see Nature 439, 768–769; 200610.1038/439768a). As we report on page 586 of this issue, these cuts have now been partially rescinded, but the discipline's future remains cloudy.
Setting aside for now the difficulties of allocating a constrained NASA science budget, the fundamental scepticism voiced by some of astrobiology's critics is misplaced, for at least two reasons. The first is the timescale of space science. Ten years is no time at all in terms of mission planning — and as a result there has not yet been a single astrobiological space mission. The first two that might make it off the launch pad will get under way in the next couple of years: the Kepler mission, which will look for planets the size of Earth circling other stars in orbits that might allow liquid water at the surface, and the Phoenix lander, which will look for organic molecules in ice on Mars. Both are important missions, Kepler profoundly so.
The second reason is a misunderstanding — sometimes wilful, sometimes not — concerning the nature of astrobiology itself. Although the field was cooked up, in part, out of political necessity, as a means of bundling together research programmes on exobiology, other life sciences and planetary science, it has at its core a powerful unifying idea. Whereas exobiology specifically took life elsewhere in the Universe as the object of its study, astrobiology looks at life in the context of the Universe — in the context, that is, of astronomy and planetary science. Thus astrobiology legitimately broadens the terms of exobiology to include the study of life on Earth, which in this context is just another planet — albeit one to which we enjoy privileged access.
The inclusion of studies of life on Earth in astrobiology has provided opportunities to re-brand existing work. It appears that many microbiologists with an interest in extremo-phile microbes have suddenly become astrobiologists, because astrobiology is — or was — where the money is. But it has also provided the field with a coherence that exobiology always lacked.
Life arises in an astronomical context, and Earth itself is part of that context. It is an intersection of the local and the cosmic, of the deepest time and the newest intelligence. Astrobiology has given this perspective an institutional home. Some second-rate research may have been funded on occasion, thanks to the astrobiology moniker's modishness. But the science indeed has a subject. It is a powerfully evocative one, which resonates not just with scientists, but with a wider public as well.