The tardigrades commonly called water bears, space bears, or moss piglets due to their appearance and movement, constitute a phylum of Ecdysozoa within the animal kingdom, characterized by being invertebrates, protostomes, segmented and microscopic (500 μm on average).
They are grouped within a large cluster of paratropes by presenting characters that suggest that they share a common ancestor with arthropods, along with onychophores.
The tardigrades were described for the first time by Johann August Ephraim Goeze in 1773, who named them water bears (from the German Kleine Wasser-Bären, literally ‘water bears’) and refers to the way they walk, similar to the movement of bears.
Later, the term tardigrade (meaning “slow pace”) was given by Lazzaro Spallanzani in 1777 precisely because of the slowness of this animal.
They are resilient organisms under extremophile conditions, with unique characteristics in the animal kingdom such as being able to survive in the vacuum of space, at very high pressures 6000 atm (the atmospheric pressure on the surface of the Earth is 1 atm, so they can resist atmospheric pressures 6000 times higher), they have the ability to survive at temperatures of -200 ° C and up to 150 ° C, and can withstand prolonged dehydration (they can live for up to 10 years without water). Tardigrades are also able to withstand ionizing radiation.
These bizarre creatures are most likely to outlive everything until our Sun eventually swells up and becomes a red giant.
Precisely this is why they could become the first interstellar species, as scientists plan to send Tardigrades and the nematode worm on a spacecraft that will leave our solar system.
“These are real interstellar passengers,” says Philip Lubin, head of the Starlight program at the University of California, Santa Barbara, which is planning one such interstellar journey, according to Space.com.
“We are developing the capability to test whether terrestrial life as we know it can exist in interstellar space by preparing small life-forms… C. elegans and radiation-resistant tardigrades… which are ideal candidates to be our first interstellar travelers.”
Scientists are currently working on a safe plan on how to store these tiny—yet bizarre—creatures in a state known as anhydrobiosis—a dormant state induced by drought in which an organism becomes almost completely dehydrated and reduces its metabolic activity to an imperceptible level.
Scientists plan to wake them up at a specific time during their journey across the stars and study them in detail.
This unprecedented mission will provide scientists with a better understanding of how organisms could survive long cosmic journeys, but also offer insight on how life in general could spread across the universe.
“Besides being microscopic, and thus conveniently fitting on our first interstellar wafer craft, they can be frozen and put into a state of anhydrobiosis, meaning they can be dehydrated and put into suspended animation,” the team wrote on the project website. “When they are re-hydrated, they wake up as good as new!”
“Clearly, there are many technical challenges. This is a long-term humanity-changing program,” Lubin said. “The biggest challenge is that NASA, the U.S. government, does not plan 30 to 50 years ahead in space. Perhaps a public/private alliance is needed. Similarly, what may be required is a new division of NASA or new agency whose mandate is interstellar flight.”