It can survive drying out, extreme heat and cold, and even exposure to vacuum.

The humble tardigrade, only about a millimeter long, can be found practically anywhere there’s enough water for it to live, and quite a few places there isn’t.

This weird, ugly-cute little guy’s secret comes down to chemistry.

There aren’t just one or two kinds of tardigrade.

Tardigrades are actually a giant group of animals including over a thousand species, and that diversity helps explain their widespread habitats and lifestyles across the globe.

Technically, all tardigrades are aquatic.

But many can actually be found in habitats where water isn’t always available, like lichens or moss cushions -- places where small amounts of water can collect and then dry out.

To survive until water comes back, some species of tardigrade can enter a state of suspended animation called anhydrobiosis -- a word that translates to life without water.

Now, being alive without water is not easy.

Remember that you and I are about 60% water.

All of the biochemical reactions that keep us alive, they take place dissolved in water.

The structures that make up our cells depend on water to hold them together.

Water’s hydrogen bonds keep everything in place.

Without water, we literally wouldn’t even have a shape.

So tardigrades don’t dry out completely, but they do desiccate to something like 5% water -- which would kill most animals.

Scientists have wondered for years how the tardigrades do it.

Some animals, like brine shrimp, survive drying out by producing lots of a sugar called trehalose .

Trehalose can make up as much as 10-20% of these animals’ body weight when they dry out -- imagine being 20% sugar!

I mean, I know you’re sweet but you’re not that sweet.

And it’s not just animals -- some bacteria, archaea, and yeast seem to use trehalose to resist drying out as well.

This sugar seems to stabilize cellular structures as water drains away, keeping the creature relatively safe until they’re exposed to water again.

But studies of trehalose in tardigrades have been inconsistent.

Some species seem to have none.

Others have some, but nowhere near 20%.

They also don’t seem to have the genes needed to make trehalose in the first place.

A study published in 2017 found that tardigrades have evolved a mechanism all their own for when their water supply dries up.

Their genes code for a tardigrade-specific set of proteins called TDPs.

Most proteins have an ordered structure that gives them a specific biochemical function.

But TDPs are disordered.

Floppy.

Loosey-goosey.

When water starts getting scarce, tardigrades respond by making lots of floppy-loosey goosey TDPs.

And as the tardigrade’s cells start to dry out, the TDPs start standing in for water, filling in the gaps, and holding everything in place.

The studies showed the TDPs actually immobilize the tardigrade’s body in a state kinda like glass.

This process is called vitrification.

It’s actually not too different from how trehalose works.

Evolution just has come up with two very different ways to keep different creatures alive under extreme conditions.

But we all know that tardigrades are cooler.

Thanks for watching, and thanks to Glenn for alerting us to the chemical awesomeness of tardigrades.

OK Glenn, we made this video, can we have a raise now?

Glenn?

Glenn Glenn Glenn Glenn?

Glenn.

Glenn?

Glenn.

Glenn.

Glenn.

What a minute, that’s not Glenn, that’s Steve.