I used to think tardigrades were just cute microscopic bears—turns out they’re basically indestructible.
These eight-legged micro-animals, roughly half a millimeter long give or take, have survived conditions that would obliterate most life on Earth. We’re talking temperatures near absolute zero, the vacuum of space, radiation doses thousands of times higher than what would kill a human, and pressures six times deeper than the Mariana Trench. When Thomas Boothby at the University of Wyoming put tardigrades through a particle accelerator in 2020, some of them survived doses of heavy-ion radiation that would turn human DNA into confetti. The really weird part? They just shrugged it off and kept going. No drama, no fanfare—they simply rehydrated and started crawling around like nothing happened. I’ve seen videos of them lumbering through moss samples, and honestly, they look completely unbothered by existence itself.
Here’s the thing: their survival trick isn’t about being tough in the traditional sense. It’s about playing dead better than anything else on the planet.
The Cryptobiotic State and the Glass That Protects Them From Basically Everything
When conditions get bad—really bad—tardigrades enter what scientists call cryptobiosis, which is a fancy way of saying they pause their metabolism to nearly zero. They expel almost all the water from their bodies, sometimes retaining less than 3% of their normal water content, and curl into a dried husk called a tun. Wait—maybe “husk” sounds too fragile. It’s more like a time capsule made of flesh. During this process, they produce massive amounts of a protein called Dsup (Damage suppressor) and a sugar called trehalose that forms a glass-like matrix around their cellular structures. The trehalose essentially replaces water molecules and locks everything in place, protecting DNA and proteins from falling apart. Researchers at the University of Tokyo found that this glassy state can preserve tardigrades for decades—possibly longer, though we don’t have definitive proof beyond roughly 30 years in the lab.
The Dsup protein is particularly fascinating because it seems to shield DNA from radiation damage by binding to chromatin. In 2016, scientists inserted tardigrade Dsup genes into human cells, and those cells showed increased resistance to X-rays. Nobody’s saying we should start injecting tardigrade DNA into astronauts, but the implications for space travel are hard to ignore.
Radiation Resistance That Makes Cockroaches Look Fragile
Tardigrades can withstand radiation levels up to 5,000-6,200 grays—for context, 5 grays is enough to kill a human. Part of this resilience comes from their ability to repair DNA breaks rapidly. When radiation shatters their genetic material, tardigrades have molecular machinery that can stitch it back together with surprising accuracy. A study published in Nature Communications in 2016 revealed that tardigrades possess unique proteins that protect their DNA from hydroxyl radicals—the destructive byproducts of radiation exposure. I guess it makes sense evolutionarily, since they live in environments like high-altitude moss that recieves intense UV radiation. But still, the sheer scale of their resistance is almost absurd.
Some species, like Ramazzottius varieornatus, are more radiation-resistant than others, which suggests that even within tardigrades, there’s a spectrum of invincibility.
Surviving the Vacuum of Space and Extreme Pressure Without Breaking a Sweat
In 2007, the European Space Agency launched tardigrades into low Earth orbit as part of the FOTON-M3 mission. They were exposed to the vacuum of space, cosmic radiation, and solar UV for 10 days. When they came back, some of them—not all, but some—revived and even reproduced. That’s not supposed to happen. The vacuum of space should cause cells to explode or collapse, but tardigrades in their tun state are so dehydrated that there’s nothing left to expand or rupture. Meanwhile, they’ve also been subjected to pressures exceeding 600 megapascals in lab experiments—about six times the pressure at the bottom of the ocean—and they survived that too. The mechanism isn’t entirely clear, but researchers suspect that their compact, dehydrated form simply doesn’t have the structural vulnerabilities that pressurized water would create. Anyway, it’s become a running joke among astrobiologists that if we ever find life on Mars, it’ll probably be a tardigrade we accidentally brought with us.
Temperature Extremes That Would Freeze or Boil Almost Anything Else
Tardigrades have been cooled to -272°C (just one degree above absolute zero) and heated to 151°C, and they’ve survived both. At those temperatures, molecular motion nearly stops or proteins denature instantly—except in tardigrades, where the trehalose glass and other protective molecules keep cellular structures intact. There’s something almost exhausting about how casually they survive these extremes. A 2020 study found that tardigrades frozen in Siberian permafrost for roughly 24,000 years were successfully revived, though the exact age is still debated. I used to think hibernation was impressive, but this is on another level entirely—this is biological suspended animation with no off switch required.
Honestly, the more I read about tardigrades, the more I wonder if “extreme” is even the right word for conditions they face. To them, maybe it’s all just weather.
