Primula Baggins wrote:There's more to the question of life on other planets than satisfying our curiosity. Imagine being able to study how other forms of life, forming in an entirely separate environment, solved the same problems life on Earth faced. The results could have huge implications. Just the existence of life another world has huge implications, philosophical as well as scientific, even if it's just bacteria, or fossil bacteria as might be the case on Mars. (And I'm willing to bet we'll find a lot more than bacteria around those warm undersea vents on Europa.)
As much as I like knowing more about the cosmos, I'm leaning to the position that the high costs of space exploration mean we should approach it with caution. Everyone is thrilled by the
Curiosity rover, for example, but $2.5 billion dollars seems like a hell of a lot to me to bring back some (in my view) pretty unclear pictures of Mars. A world that we already know enough about to know that it doesn't have all that much to offer us any time in the foreseable future. And with the economic situation as it is now, and as it is likely to continue, the idea of manned Mars exploration strikes me as insane.
I don't think that we should stop sending these probes. The New Horizons mission to Pluto, for example, will bring us images that we've never seen before. But it may be that Europa is a dead world with ice running straight down to rock and the proposed undersea oceans nothing but science fiction.
At risk of heresy, I see space exploration in the same terms as building sports stadiums. Certainly a justifiable use of public money but hardly a priority.
Primula Baggins wrote:Venus can't support life and I would bet it never has. The surface is the temperature of boiling lead at incredible pressures, and the clouds themselves are sulfuric acid. Life needs a mild, controlled environment, at least within the body and within the cell, in order to grow and replicate. It needs not to be burned to a crisp or oxidized by powerful acid. Liquid water and a source of energy. . . .
Wiki suggests that, at one point, Venus was much more earth-like and probably had significant amounts of liquid water. The runaway greenhouse effect only came later. Still, good luck to any attempt to fossil-hunt there.
Primula Baggins wrote:Some people theorize that life on Earth first formed down near our own undersea vents, when the surface was still being bombarded and had a poisonous atmosphere. It also at least used to be suspected that life may have been arisen on Earth several times, only to be smacked down by a catastrophic impact, before the form that led to us (among other things) escaped that and took hold.
I think it likely that life on earth arose several times (I wouldn't be surprised if photosynthesis and chemosynthesis had different origins). The way in which these life forms are similiar suggests to me that life on other worlds would share many of those similarities.