Tardigrades Can Survive in Space

The remarkable resilience of tardigrades, often called water bears or moss piglets, stems from their ability to enter a state of suspended animation known as cryptobiosis. This process involves the organism showing no visible signs of life and its metabolic activity nearly stopping. First described in 1773 by German zoologist Johann August Ephraim Goeze, these microscopic invertebrates can be found in diverse environments across the globe, from mountaintops to the deep sea. Their most notable survival mechanism is anhydrobiosis, or "life without water," where they can lose up to 97% of their body's moisture, shriveling into a desiccated state called a tun. In this form, they can withstand conditions that would be fatal to almost any other life form.

This incredible durability was put to the ultimate test in 2007 during the FOTON-M3 mission. Dehydrated tardigrades were exposed to the vacuum of space and solar radiation for 10 days. Upon their return to Earth and subsequent rehydration, many of the tardigrades that were shielded from the sun's radiation revived and even produced viable embryos. While exposure to the combination of a vacuum and solar UV radiation was more detrimental, some still survived. This experiment marked the first time an animal had survived such direct exposure to the harsh environment of outer space.

The secret to their survival lies in a combination of factors. During cryptobiosis, their metabolism slows to less than 0.01% of its normal rate. They produce special sugars and unique proteins, known as tardigrade-specific proteins, that are thought to protect their cells from damage during dehydration. This state allows them to endure not just the vacuum of space, but also radiation levels thousands of times higher than humans can withstand, and extreme temperatures. They have been experimentally subjected to temperatures as low as -272.95 degrees Celsius and as high as 150 degrees Celsius and have been revived.