[s1artibartfast]

Colision with a planet or moon would do it, anything that turns the surface to lava really.

[sebzim4500]

Even then there's a chance a few tardigrades hibernate on some material that shoots up and then comes back a few years later once the earth has cooled a bit.

[LeifCarrotson]

I propose we do this intentionally - put a few tardigrades and some other extremophiles in a rad-shielded container inside a fully-passive reentry vehicle and throw it up into a graveyard orbit for a couple million years. Cheap insurance for life on earth!

[pfdietz]

I think they could be cooked by thermal radiation as the ejecta expands.

[sebzim4500]

Probably most would be, but there are a lot of microorganisms and only a few need to get lucky.

[blooalien]

Tardigrades were placed in the "extremophile" class with good reason. If anything could survive a truly catastrophic impact event, I'd say the smart money goes on the lowly "water bear" to win. :)

[Keysh]

Tardigrades are not "extremophiles", which refers to organisms that live (grow, reproduce) in "extreme" environments ("phile" = "like, love"). Tardigrades can temporarily survive some rather extreme conditions, but they generally require fairly ordinary environments to actually live. (As suggested by common names like "water bear" and "moss piglet".)

[dekhn]

Deep-earth chemoautotrophs might survive that. But ultimately, if the deep subsurface exceeds 150C, it would be hard to survive.

[fecal_henge]

Intollerable stuffyness.