Tardigrades Survive Outer Space

The vacuum and radiation of outer space are lethal to almost all known life, but for the microscopic tardigrade, it's a manageable challenge. These eight-legged invertebrates, affectionately known as water bears or moss piglets, can enter a state of suspended animation called cryptobiosis to endure conditions that would instantly kill most other organisms. To do this, they retract their legs, curl into a desiccated ball called a tun, and replace nearly all the water in their cells with protective sugars and proteins. This glassy mixture prevents their cellular structures from collapsing or being destroyed by ice crystals in freezing temperatures.

This incredible ability was put to the ultimate test in 2007, when the European Space Agency sent tardigrades into low-Earth orbit on the FOTON-M3 mission. Clinging to the outside of the satellite, they were directly exposed to the hard vacuum and intense solar radiation of space for ten days. Upon their return to Earth and rehydration, many not only survived but went on to successfully reproduce. Their resilience is largely owed to an extraordinary ability to repair DNA that has been shredded by cosmic radiation, a skill that allows them to seemingly come back from the dead. This capacity for long-term suspended animation is so profound that some specimens have been successfully revived after being frozen (Review) in Antarctic moss for over 30 years.