Tardigrades are microscopic animals blessed with two very cool nicknames — the water bear and the moss piglet. They are segmented and reach a maximum length of a millimeter, maybe a millimeter and a half. That's about this big:

Water bears are as indestructible as they are tiny. They've been known to survive in temperatures as cold as minus 459 degrees F and as hot as 304 degrees F. They shrug off extreme doses of radiation and laugh in the face of the silent vacuum of space itself. In an experiment in 2007, water bears were exposed to outer space for 10 days. After returning to Earth it was discovered that a lot of the bears survived and some even had babies.

Called "Earth's hardiest animals," these resilient creatures have long been the subject of scientific curiosity.

A team of Japanese researchers recently figured out the secret behind the hardy critter's amazing survival capabilities. They discovered that among the animal's many coping strategies is a protein that protects its DNA from radiation damage. The researchers named it "Dsup" (short for "damage suppressor"). When the scientists transplanted the Dsup protein into human cells in the lab, they found it protected those cells too.

The scientists suggest that the finding means that genes from these "extremeophiles" could one day be used to protect humans from radiation, perhaps from X-rays, for example.

The study was published in the journal Nature Communications.

Interestingly, the tardigrades were more resistant to radiation than the human cells that the researchers manipulated by adding Dsup protein.

"[So] tardigrades have other tricks up their sleeves, which we have yet to identify," Professor Matthew Cobb from the University of Manchester, who was not involved with the study, told the BBC.

Cobb said that in principle, "these genes could even help us bioengineer organisms to survive in extremely hostile environments, such as on the surface of Mars - [perhaps] as part of a terra-forming project to make the planet hospitable for humans."

Water bears certainly are massively interesting little creatures. Here's video of a tardigrade captured from a backyard pond that's worthy of a watch.

Editor's note: This story was originally published in September 2011, and has been updated.