First described in 1773 by Johann August Ephraim Goeze, who called them kleiner Wasserbär, meaning ‘little water bear’ in German, Tardigrades are microscopic water-dwelling, segmented animals with eight legs. They aren’t related to any other species and some scientists have gone as far as to deny their existence.
The name Tardigrada means “slow walker” and was given by Lazzaro Spallanzani in 1777. The name water bear comes from the way they walk, reminiscent of a bear’s gait.
Tardigrades have a digestive tract, hard exoskeleton, and produce by eggs for reproduction. They can create their own suspended animation, enabling them to dehydrate and rehydrate for long periods of time. Some can reach 100 years old and the largest adult Tardigrades may reach a body length of 1.5 millimeters.
Tardigrades can survive extreme environments that kill almost every other animal. They have been known to survive temperatures ranging from near absolute zero (−459 °F) to temperatures as high as 304 °F. They can withstand 1,000 times more radiation than other animals and can live almost a decade without water in suspended animation.
Tardigrades, unlike any other known animal, can survive in space. They can and do live in any environment on Earth, as well. Since 2007, tardigrades have also returned alive from studies in which they have been exposed to the vacuum of outer space for a few days in low Earth orbit.
It seems probable that since these amazing creatures can survive in space, they may not have originated on Earth, but rather ended up here by chance. It is plausible that they might have come from elsewhere in space, possibly carried here on an asteroid or meteorite.
If it is possible for Tardigrades to travel through space, than perhaps we all came from other planets, carried here through the void of space. Could it be possible that these organisms, or ones similar to Tardigrades, could have seeded life on this planet and/or others?