One of the most incredible creatures on Earth is one so small we can only see it with a microscope. This tiny animal, called a tardigrade or “water bear”, is only about a millimeter long, and yet it can survive an amazing range of conditions. Hot, cold, dry, wet, and even the vacuum of space – somehow, the tardigrade can survive them all.
Tardigrades prefer to live in lakes, on moist pieces of moss, or other wet environments. However, they can survive in extremely dry environments. In 1995, after 8 years of no water, dried tardigrades were brought back to life. It turns out when a tardigrade dries out, it retracts its eight legs and its head. It then sheds almost all the water in its body, slows its metabolism to only 0.01% of the normal rate, and enters a state of suspended animation. While in this state, a tardigrade is known as a “tun”. Tardigrades can stay this way for decades and reanimate upon coming into contact with water. If a tardigrade stays in the tun state for too long, its DNA gets damaged – however, after it awakens, the tardigrade can fix it.
Tardigrades also have the ability to survive a huge range of temperatures. Testing in labs has revealed that tardigrades can survive being frozen to -272.8 °C (absolute zero is -273.15 °C). The lowest temperature recorded on Earth was -89.2 °C in Antarctic in 1983. On the other end of the scale, tardigrades are known to survive at temperatures over 148.9 °C. The hottest temperature on Earth is about 56 °C. Not only can tardigrades deal with a variety of temperatures, they can also survive large amounts of radiation. Tardigrades have been known to survive lethal doses of x-rays, alpha radiation, gamma radiation, and UV radiation.
Finally, tardigrades seem to endure both high pressure and the vacuum of space. Studies have shown that tardigrades in the tun state can survive pressures of up to 600 MPa (megapascals). For comparison, the deepest part of the ocean, the Mariana Trench, has a pressure around 100 MPa. Other studies reveal that tardigrades survived being in a low orbit around Earth, exposed to the vacuum of space and radiation. It seems this little “water bears” have the power to survive in the most incredible range of environments.