Tardigrades: The Toughest Animals in the Universe
TL;DR Summary
They can survive radiation, extreme heat, the vacuum of space, and decades without water. Meet the microscopic water bear.
If you were asked to name the most indestructible creature on Earth, you might guess a cockroach. But the true masters of survival are microscopic, eight-legged invertebrates known as Tardigrades, or "water bears."
Usually no larger than half a millimeter long, tardigrades live in moss, lichen, soil, and water all over the world. But their ability to survive extreme conditions is nothing short of alien.
The Tun State
When conditions become lethal—such as intense heat, freezing cold, or complete dehydration—tardigrades enter a state of suspended animation called cryptobiosis, or the "tun" state.
They curl up into a tiny ball, retract their legs, and slow their metabolism to less than 0.01% of normal. They replace the water in their cells with a special sugar called trehalose and a unique protein that prevents their internal structures from shattering.
In this dormant state, they are practically invincible.
Surviving the Unsurvivable
In the tun state, tardigrades have been proven to survive:
- Extreme Temperatures: From just above absolute zero (-272°C) to well past the boiling point of water (150°C).
- Extreme Pressure: They can survive pressures six times greater than those found at the bottom of the Marianas Trench.
- Radiation: They can withstand hundreds of times the lethal dose of gamma radiation for a human. They possess a unique "damage suppressor" protein that physically binds to their DNA, shielding it from breaking.
- Decades without Water: Tardigrades have been revived after sitting completely dry for over 30 years.
Water Bears in Space
In 2007, the European Space Agency launched the TARDIS (Tardigrades in Space) experiment. They exposed living tardigrades directly to the hard vacuum, extreme cold, and brutal cosmic radiation of low-Earth orbit for 10 days.
When brought back to Earth and rehydrated, the majority of the tardigrades woke up, resumed their normal lives, and even reproduced successfully.
In 2019, an Israeli lunar lander named Beresheet crashed onto the surface of the Moon. It was carrying thousands of dehydrated tardigrades in its payload. Because they can survive extreme impacts and the vacuum of space, scientists believe it is highly likely that thousands of dormant tardigrades are currently scattered across the lunar surface, waiting for a drop of water that will never come.