Vacuum (imposing extreme dehydration) and solar/galactic cosmic radiation prevent survival of most organisms in space [1]. Only anhydrobiotic organisms, which have evolved adaptations to survive more or less complete desiccation, have a potential to survive space vacuum, and few organisms can stand the unfiltered solar radiation in space. Tardigrades, commonly known as water-bears, are among the most desiccation and radiation-tolerant animals and have been shown to survive extreme levels of ionizing radiation [2, 3, 4]. Here, we show that tardigrades are also able to survive space vacuum without loss in survival, and that some specimens even recovered after combined exposure to space vacuum and solar radiation. These results add the first animal to the exclusive and short list of organisms that have survived such exposure.

Current Biology — Jönsson et al..

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Water-bears can be seen here.

Tardigrade Fossil range: Early Cambrian to Recent[1]
The tardigrade Hypsibius

[full article]

I covered a bit of the concept of “Panspermia” in my Spore review.  This looks like a possible culprit, as the dang things can surive /scary voice/ the vacuum of spaaace1! /scary voice/.