|The Gliese star (photo from BBC)|
Being a good 'host' may be rather moot, as far as earth life is concerned, because we can't even go to the moon any more, which at 250,000 miles away is slightly closer than the Gliese 581g planet. But with a big enough gas tank (probably will require ethanol from corn, argues Cargill) and enough Twinkies and Tang, and thick enough radiation shields, the NASA vehicle could get there within about 3 working lifetimes if it could go at, say, 1/3 the speed of light (that sluggish rate for reasons of fuel economy). Of course, that means the vehicle will require dessication facilities for the initial astronauts, not to mention appropriate privacy so that succeeding generations could be conceived.
The quest for life out there is interesting and even thought-provoking if there were even a shred of evidence for it. Of course some, including Francis Crick, argued that life here had been seeded from visiting spacecraft (dumping garbage, presumably). Martians may be watching us, of course, but if so they're keeping mighty quiet about it.
We were discussing extraterrestrial life with a friend of ours, David Krakauer at the Santa Fe Institute. One of the problems with understanding the lack of results from years of SETI (with countless computers scanning for electromagnetic radiation-based signals from intelligent life out there) is how long the signal takes to get here, now at least 20 years based on this recent discovery, relative to when such high-IQ life existed or how long it would exist, or whether and how it would be sending signals to life that is 'out there' for them--us! It is not at all clear that even if life does, did, or will exist elsewhere, that we could expect to detect it. So one can believe what they want to believe about it.
Of course, from a scientific point of view, what counts as 'life'? Need it be based on water? Is the basic energy cycle, that also generates protein and DNA components on earth, necessary for what we'd call life? If the right ingredients are present, would such life inevitably occur? Could anyone really argue that DNA as protein code would be inevitable? And if it were, is there any reason for that to generate anything that resembles human beings or human intelligence?
Many have argued in the positive, while others think that is asking too much. There could be self-perpetuating, energy-grabbing, life that is nothing like what we are like. Finding that might be more deeply interesting than finding DNA-based slime molds dozens of lightyears away.
Probably, each of us has our own preferred sci-fi scenario. Undoubtedly astronomers will continue to discover the planetary targets of Trekkies of the future.