I believe if you look at their genetics they fit snugly within the tree of life

This is one of my favourite websites, and I share it all the time:

https://www.onezoom.org/life.html/@=111445?img=best_any&anim...

(hopefully that links to the right place)

I don’t want to speak for the OP but I read their comment as “why did they evolve certain features that wouldn’t have be reasonable given the evolutionary pressures of earth?” E.g., their ability to survive high levels of radiation or vacuum.

There’s some speculation that a large amount of their genetics were transferred from other animals.[1] I wonder how much this muddles the tracing through the evolutionary tree.

[1] https://www.pnas.org/content/112/52/15976.abstract

> E.g., their ability to survive high levels of radiation or vacuum.

If I recall correctly, the tardigrades (and extremophiles like D. radiodurans) have evolved to handle damage brought on by desiccation. As a fortunate side-effect, this general robustness also protects against radiation.

What would be the odds that other planets/habitats have a similar "tree of life"? I don't know. Given the huge number of similarities in DNA, I'd say it's extremely small.

tardigrades might have some very cool properties, but nothing out of the ordinary.