Water Bears are the Only Known Animals to Survive in Space fact

Can Water Bears Survive Outer space?

Water bears (tardigrades) are the only known animals to survive the vacuum of space. Water bears are extremophiles, meaning that they can survive extreme conditions (like high temperatures, and high pressure).

Water bears are good at surviving extreme conditions due to their genetic makeup which allows them to dehydrate and then rehydrate years later when conditions improve. You can see this for yourself by soaking moss (where water bears like to live) in water (as show in the videos below).

FACT: Given their ability to survive space, some people speculate that water bears may actually come from another planet.

What Are Water Bears?

Tardigrades (also known as water bears or moss piglets) are water-dwelling, eight-legged, segmented micro-animals. There are more than 1,150 species of tardigrades. All adults of the same species of water bears have the same number of cells, but each species can differ in the makeup of organs, cells, and size.^[1]

Why Are They Called Water Bears?

Water bears get their name from the way they walk, which resembles a little bear. They also get their name from the fact that they can often be found on barnacles or by soaking moss in water.

FACT(ISH): Water bears also enjoy long walks on the beach. Any walk is long for a water bear as they have four pairs of stubby little legs and range from 0.3 to 1.2 mm (0.012 to 0.047 in) in length.^[1]

How Can Water Bears Survive In Outer Space?

The reason water bears can survive outer space is that they can withstand extreme conditions of all sorts. Their resilience makes them perfect for the inhospitable conditions of outer-space.

The extremophile water bears can^[1]:

• Withstand temperature ranges from −458 °F (−272.222 °C) to 300 °F (149 °C)
• Survive dehydration for years. When exposed to extremely low temperatures, their body composition goes from 85% water to only 3%. This dehydration ensures they don’t get torn apart by water expanding as it freezes in extreme temperatures.
• Withstand pressure ranges up to six times greater than is found in the deepest ocean trenches.
• Survive ionizing radiation at doses hundreds of times higher than the lethal dose for a human.
• Probably survive other extreme conditions like environmental toxins.

Why Can Water Bears Survive In Extreme Conditions?

Water bears use techniques like dehydration and rehydration to survive in extreme conditions, but how did they get these abilities?

It’s likely water bears have acquired the DNA to survive extreme conditions from other organisms throughout their evolution.

A stunning 17.5 percent of water bear DNA is made up of foreign DNA. That means 17.5% of a water bear’s DNA is “borrowed” from another organism.^[2]

When water bears dehydrate their DNA becomes brittle, and it can easily break apart and assimilate DNA from other organisms (like bacteria). It is thought that the assimilated foreign DNA is part of what allows them to survive extreme conditions. It’s also possible that their genetic reassembling ability has allowed for beneficial genetic mutations of their DNA.

FACT: Water bears are not the only animal to have evolved by assimilating beneficial DNA from other organisms. That is how we think plants and animals on earth evolved.

Did Water Bears Come From Space?

In a broad sense, we are all from space (i.e. we are made of bits of stardust originating during the big bang, according to basic evolutionary theories). But if we ask a more specific question, “since water bears can survive in space, and they have foreign DNA, did they originate as an organism somewhere else and then travel here through space?” We don’t know the answer.

It’s possible that the water bear has at some point been an interplanetary traveler (possibly carried to earth by a meteor or other celestial impact event). It’s also possible that some other organisms, specifically non-animal organisms like bacteria and archaea, could have come from space this way as well.