Earth's toughest creature — the tiny 'moss piglet' — can survive the equivalent radiation dose of 25 hours at Chernobyl ground zero by making a protein shield.

'Moss piglets' — also known as tardigrades, or 'water bears' — are bizarre, microscopic water-dwelling animals capable of surviving in extreme environments.

They can tolerate heats of 300°F (150°C) to the coldness of space, dry out and revive years later and stand pressures six times those found in the Mariana Trench.

They can also survive a thousand times more radiation than other animals, thanks to a unique protein they produce called 'damage suppressor', or Dsup, for short.

Analysis of this protein has now revealed how it works, by connecting to the cell complex that contains DNA and creating a protective cloud-like shield around it.

Molecular biologist James Kadonaga and colleagues at the University of California, San Diego developed three different methods to purify the Dsup protein from tardigrades to study how it works at the molecular level.

'We now have a molecular explanation for how Dsup protects cells from X-ray irradiation,' Professor Kadonaga told ScienceAlert.

'We see that it has two parts, one piece that binds to chromatin and the rest of it forming a kind of cloud that protects the DNA from hydroxyl radicals.'