Water Bears Can Survive Being Boiled and Frozen

Few creatures on Earth can cheat death quite like the tardigrade. These microscopic invertebrates, often called water bears or moss piglets for their lumbering, bear-like gait, can enter a state of suspended animation known as cryptobiosis. This isn't just a deep sleep; it's a near-total shutdown of all metabolic processes to less than 0.01% of their normal rate, allowing them to endure environments that would instantly destroy almost any other known life form.

The key to this incredible resilience is a process of extreme dehydration. When faced with lethal conditions, a tardigrade expels over 95% of its body's water, curling into a desiccated, lifeless-looking ball called a tun. Inside its cells, special sugars and proteins form a protective, glass-like matrix in a process called vitrification. This glassy substance locks delicate cell structures and molecules in place, protecting them from being shredded by ice crystals when frozen (Review) to near absolute zero or unraveling from heat well above the boiling point of water.

First discovered in 1773 by German pastor Johann Goeze, their remarkable ability wasn't evolved for surviving the vacuum of space, but for a more common problem: the temporary drying out of the watery moss, lichens, and leaf litter they call home. Once conditions become hospitable again, even centuries later, the tardigrade can rehydrate and return to life, often in just a matter of minutes.