Tardigrades Turn Themselves Into Glass to Survive Space, Radiation, and Extreme Cold

A tardigrade can be cooled to within a fraction of a degree of the coldest temperature the universe allows, kept there, and then revived with nothing more than a drop of water. The same animal can survive intense radiation, the airless vacuum of space, and decades of deep freeze. It sounds like science fiction, but it is documented science, repeated across dozens of studies and even tested aboard the International Space Station. What makes this possible is not raw toughness. It is a biological trick so sophisticated that researchers are now borrowing it to protect astronauts and cancer patients.

Tardigrades are microscopic animals, typically less than a millimeter long, found in damp moss, soil, and freshwater on every continent including Antarctica. They have eight legs, a rounded body, and a face that looks surprisingly expressive under a microscope. In normal conditions they eat algae and bacteria, reproduce, and live ordinary lives. But when the environment becomes life-threatening, they activate a survival strategy called cryptobiosis, a word derived from Latin that means hidden life. In this state the animal is not simply dormant, the way a bear hibernates through winter. It is something much more extreme than that.

When a tardigrade senses danger, it pulls in its legs, expels almost all the water from its body, and curls into a compact barrel shape called a tun. Inside its cells, the loss of water triggers special proteins to take over. These proteins, called tardigrade-specific intrinsically disordered proteins, or TDPs, have no fixed shape in normal conditions. They flow loosely through the cell’s interior fluid, called cytoplasm. But as water disappears, they collapse around the cell’s most important structures, including the membranes, the DNA, and other proteins, and they solidify into an amorphous, non-crystalline solid. In plain terms: they turn into glass. A 2017 study in the journal Molecular Cell, led by Thomas Boothby at the University of North Carolina, confirmed that this glassy state is the actual mechanism of protection, not a side effect of it. When researchers disrupted the proteins’ ability to form glass, the tardigrades lost their ability to survive drying.

Glass might seem like a strange protective material, but it works for a very specific reason. A crystal is an ordered structure, and when proteins or ice form crystals inside cells, the sharp geometric edges shred the delicate membranes from the inside. Glass has no such structure. It is disordered and smooth, which means it can surround fragile molecules and hold them perfectly still without damaging them. Think of it like packing a fragile ornament not in rigid foam with hard corners, but in a soft substance that hardens around its exact shape. When water is added back, the glass dissolves, the proteins return to their loose state, and every biological process resumes from the exact point where it stopped. The tardigrade does not recover. It simply continues.

This is why tardigrades can be revived after extraordinary periods of time. Japanese researchers published a study in 2016 documenting the revival of tardigrades from moss samples that had been frozen at minus 20 degrees Celsius for 30.5 years. Two adults and one egg were successfully revived. The egg hatched, the animals reproduced, and their offspring were healthy. The recovery was slow, taking about two weeks before the first animal could crawl properly, but it worked. The key detail is that the animals were not running a slow internal clock during those decades. Time, in any biological sense, had simply been switched off.

Tardigrades also carry a separate protein called Dsup, short for damage suppressor. Research published in Nature Communications in 2025 showed how Dsup physically wraps around chromatin, the tightly packaged structure that holds DNA, and acts as a shield against ionising radiation. Ionising radiation, the kind produced by X-rays and radioactive material, damages DNA by generating highly reactive molecules called hydroxyl radicals. Dsup absorbs the attack before it reaches the DNA strand. Researchers have transferred this protein into yeast, human cells, plants, and fruit flies, and it works in all of them. Scientists studying how to protect astronauts on long missions to Mars, where radiation exposure is a serious risk, are paying close attention.

In 2025, a tardigrade species discovered at the Indian Institute of Science was sent to the International Space Station aboard the Axiom-4 mission. Astronaut Shubhanshu Shukla rehydrated the dried animals in orbit while the research team watched on a live video feed from Bengaluru. After a tense hour, the tardigrades began to move. They walked, fed, and reproduced in microgravity, and then returned to Earth. The team is now comparing their genes to those of tardigrades that stayed on the ground, looking for biological clues about how living things cope with the stress of space. These animals have now flown on missions organized by Russia, Europe, the United States, China, and India, making them arguably the most widely traveled animals in human history.

One important qualifier: a tardigrade that is caught off guard is not particularly tough. If you freeze one suddenly while it is still walking, it dies like any other small animal would. The survival abilities only apply to the tun state, and the animal needs time to prepare for it. This is why scientists are still unsure whether any tardigrades survived the 2019 crash of the Israeli lunar lander Beresheet, which was carrying dried tardigrades as part of a research payload. The animals were already in their tun state when the craft hit the Moon’s surface, but the impact may have been too fast for even a tun to survive. No one has gone back to check, and given how valuable lunar samples are, no mission to investigate is currently planned.

Source: Space Daily