Earth from deep space

[Viking]

Nope, not a reposting of the classic Voyager 1 picture, but rather a new movie from the Deep Impact spacecraft that is currrently in its extended mission phase.

The video was recorded to get an idea as of what an Earth like extrasolar planet might look like through a telescope. A corresponding press release can be found here.

The Earth has a rather large apparent size in the video, so note that:

"To image Earth in a similar fashion, an alien civilization would need technology far beyond what Earthlings can even dream of building," said Sara Seager, a planetary theorist at the Massachusetts Institute of Technology, Cambridge, Mass., and a co-investigator on EPOXI. "Nevertheless, planet-characterizing space telescopes under study by NASA would be able to observe an Earth twin as a single point of light -- a point whose total brightness changes with time as different land masses and oceans rotate in and out of view. The video will help us connect a varying point of planetary light with underlying oceans, continents, and clouds -- and finding oceans on extrasolar planets means identifying potentially habitable worlds." said Seager.

[Reverend Joe]

and finding oceans on extrasolar planets means identifying potentially habitable worlds.

This is something that has always bothered me...

What about the bacteria on those planets? Do we just exterminate all life on the surface first or what?

[Lemur]

How confident are we that there would even be bacteria on other planets? Just how rare is life, anyway?

And what if that life was based on a completely incompatible biology? What if, for instance, the proteins were utterly different? As in, indigestible by creatures from our chemical background? Would the two biospheres co-exist, or annihilate? Any terrestrial experiments tried to address any of these questions?

[Viking]

This is something that has always bothered me...

What about the bacteria on those planets? Do we just exterminate all life on the surface first or what?

Do you mean if we should inhabit them? Habitable in this context means that life as we know it could theoretically exist there.

How confident are we that there would even be bacteria on other planets? Just how rare is life, anyway?

Basically, we got little short of no clue as of how normal life is. It could be an exceptional cosmological jackpot and that the Earth is the only place with life in the entire universe; it could be rare but yet be found here and there in the galaxy; it could be extremely normal and exist several places even in the solar system (on places such as Mars, Europa, Ganymedes, Titan, Enceladus...the list goes on) and in almost every solar system; we simply do not know. Perhaps it could even reside life in some of the craters in the polar regions on the Moon, which are speculated to contain water ice where there is permanent shadowing (not that I've seen any serious speculation on the life part).

And what if that life was based on a completely incompatible biology? What if, for instance, the proteins were utterly different? As in, indigestible by creatures from our chemical background? Would the two biospheres co-exist, or annihilate? Any terrestrial experiments tried to address any of these questions?

That would surely depend a lot.

[Hax]

Perhaps it could even reside life in some of the craters in the polar regions on the Moon, which are speculated to contain water ice where there is permanent shadowing (not that I've seen any serious speculation on the life part).

Wouldn't the lack of an atmosphere make life as we know it impossible?

[Viking]

Wouldn't the lack of an atmosphere make life as we know it impossible?

Well if it resides below the ice, it could have a local micro scale atmosphere; but as I said I haven't seen any serious speculation on this, so I should probably not have mentioned it...