What kind of life form could possibly live (and not in cryptobiosis) in space?

[Kerbface]

You hear of space whales, and then there was that bubblewrap-to-insect creature in the Ark in Space. What is realistically possible? Is it possible at all? Or maybe it is but there's no plausible way a creature could evolve to suit the environment of outer space as the environment would be too inhospitable to allow for anything to survive even a single generation?

[daveboy2000]

Well, it is plausible that single celled organisms could've adapted to total-vacuum conditions on an earthlike planet that was gradually stripped of its atmosphere over the course of thousands of years because of a dying magnetic field. In this case an organism could develop its own 'pressurized suit' that keeps the insides of the cell spill out in a vacuum. How it would feed though, is another problem, as all it would have is light from a star, tons of radiation (which is also a problem), and the occasional hydrogen atom.

So in the most optimal conditions a single celled organism COULD evolve to survive vacuum-like conditions, however how it would feed and deal with solar radiation is another thing. Riding on astroids and eating the rock (some single-celled organisms on earth do this) would be an option, providing food and partial shelter as long as the organism is on the dark side of the astroid. Then again, it is not always on the dark side and it might require the starlight for some kind of efficient photosynthesis.

[MBobrik]

in vacuum ? ordinary single cells not. Why ? they are powered by proton gradients. And hydrogen is extremely proficient at diffusing out of thin stuff. So the outer shell that would be needed to maintain all its hydrogens inside over long periods of time would have to be impractically thick.

.

Multi-celled organisms, however, could adapt to low pressure conditions by simply maintaining positive internal pressure through reinforced tissues and sealable orifices. Some birds can fly at 11 000 m and the pressure is just 1/4 of the atmospheric pressure. One big step would be, however, to store oxidizer in solid form in their bodies and be capable of acquiring it by ingesting it. The other is more radiation resistance. But this is something that can evolve on its own given selective pressure from increasing radiation. and then, from there, there would be no obstacle to adapting to complete vacuum.

[SuperFastJellyfish]

http://en.wikipedia.org/wiki/Tardigrade

I know they go through cryptobiosis, but as someone said earlier if they lived on a planet whose atmosphere was slowly stripped away over a long period of time they are already well on their way to adapting to total vacuum.

[Kerbface]

How would a spacefaring creature gain sustenance and would it have any power over it's direction of travel? Would it become a living spaceship and spurt some kind of reaction mass?