Tardigrades have survived direct exposure to the vacuum of space

Tardigrades (water bears) are microscopic, eight-legged animals that live in moss, soil, and water — under extreme stress, they can enter a state called cryptobiosis, in which their metabolism almost completely shuts down.

In this state, they dehydrate their bodies down to just a few percent of their normal water content, while their cells fill with a special protein that protects internal structures from damage — the organism essentially "suspends itself" like a computer, ready to resume later.

In space experiments, tardigrades placed outside a spacecraft, exposed directly to vacuum, cosmic radiation, and extreme temperatures, came back to life once rehydrated on Earth — and some of them went on to reproduce.

The bigger picture: this is one of the very few known multicellular organisms capable of surviving open space, which makes it a favorite example for scientists probing the outer limits of what "life" can even mean.