Tardigrades are some really, really tough little bastards. I'd hate to meet a flesheating tardigrade of human size or larger. Not without a flamethrower.
Surviving the anoxic, bitterly cold, irradiated, hard vacuum of space, shit, if life here started as particulates spiked with molecules which went on to form life eventually, or even something living came down here from outer space.. something like that, so small would have a very low terminal velocity and not drop fatally. And they might well survive re-entry IMO. Unless it was on a large object that heated up as such, but tiny, tiny grains or organisms themselves might, presenting such little mass as to heat up very little through friction, especially through the cold, thin air, in an already cryogenically inanimate form....it wouldn't altogether surprise me for a tardigrade, or a radioresistant bacterium. Who knows, LUCA might just be a (very) little green man.
And some extremophiles are just plain WEIRD, surviving around marine hydrothermal vents that under the massive pressure of so much water above, the water coming from them can be hot enough to melt lead. And weird stuff like bacteria reproducing so slowly that they might only divide once in a century or even longer. Creatures like snottites at regular pressures, living as colonies which breath H2S (hydrogen sulfide is the noxious gas that at low concentrations gives rotten eggs their nasty stench, from decomposition of aminoacids containing sulfur such as cysteine and cystine, methionine etc, and at larger concentrations, to us oxygen-breathers using iron based blood oxygen transport molecules like haemoglobin is as deadly and potentially even more insidious than hydrogen cyanide). Snottites are colonial critters that hang from cave ceilings in waterlogged or highly water flooded environments and breath in H2S, oxidizing it to sulfuric acid. So they breath poison gas and shit H2SO4!
And there are even organisms which thrive in acidic lakes with a PH equal to concentrated sulfuric acid solutions, or that are chock-full of arsenic.
Its less of a question as to what will support life...as I see things it what WON'T support live, or at least permit it to transit through such a space as they cannot actively thrive in and go into a state of stasis to re-animate when they arrive somewhere suitable for them to live in.
I myself, have seen with my own eyes, to my considerable surprise, microbial colonies growing on the top of old solutions of caustic soda (sodium hydroxide/NaOH, a pretty strong alkali that can easily cause burns to human skin and tissues), that were so strong I'd not have dipped my electronic PH meter in them for fear of corroding or etching the glass electrode, and were so concentrated as to be viscous. Like a kind of thin syrup or diluted honey in consistency, and close to or saturated with NaOH! yeah, mold, growing on that, which takes some doing to survive for a microorganism.
There are even bacterial colonies that EAT radiation, not just that survive it, but that feed on it. And also radioresistant bacteria colonies on the inside of the contaminated chernobyl reactor, that survive, and thrive there in an environment that would deliver us a lethal dose of radiation within moments. Minutes at best and that are so radio-hot they would literally cook us alive as well.
Seems that somewhere, something is hard enough to survive even the nastiest of conditions. The combination of harsh environments that is space (hard vacuum, intense solar radiation, freezing cold, no oxygen, no water, no food no anything good for a living being as we know one) like a tardigrade, that is one of the most well-adapted, hardy sons of bitches ever, that we know of. Damn.
