Not alotta of planets around other stars could support life judging by the criteria we look for now: the possible presence of liquid water. In fact none of ’em could (with the possible exception of one).
But our method for determining whether liquid water could be present is crude to say the least. It’s based on the luminosity and distance of a planet from its sun which gives a rough idea of its average temperature. If that falls into the range of liquid water, then bingo.
So a new method of calculating habitability is needed says David Speigel and his mates at Columbia University in New York, (which is itself habitable only at certain times of the year).
This new method has gotta take into account all the new things we’ve been learning about life (that it can survive at temperatures ranging from -85 degrees C to 130 degrees C), about climate models and radiative balance and about other planets themselves, most of which have much more eccentric orbits than ours and so have more extreme seasons.
It may be that on these planets only a small fraction of the surface can support liquid water and life. And if that’s the case, its signature would be too faint to spot.
It makes sense to limit our search to planets that not only have life. but enough of it to be detectable to us. Spiegel suggests that there may be some critical fraction of habitability below which we cannot detect life, even if it is there. For example, only 85 per cent of the Earth’s surface is habitable, a number which varies from year to year.
All that means that astrobiologists have got some hard work ahead of em. It also means that a re-analysis of the one planet that might harbour liquid water, a planet about 5 times Earth’s size orbiting a red dward in the constellation of Libra, might produce some encouraging results.
Ref: arxiv.org/abs/0711.4856: Habitable Climates
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