After all, we all have a weak point … or more than one. Tardigrades or water bears are known to be practically indestructible , creatures that are practically impossible to kill. They are microscopic animals classified as extremophiles , that is, capable of surviving in extreme conditions, such as radiation, temperatures of 150 ° C (positive and negative), spending long periods without drinking or eating, and even surviving in the vacuum of outer space.
Various scientific studies have played to test its limits, until at last it seems that they have found them. It turns out that there is something that tardigrades cannot survive, it is a shot from a gun (and no, the study is not American, but English, specifically from the University of Kent).
In 2019 the Israeli Beresheet spacecraft crashed into the moon. Part of its crew consisted of tardigrades taken into space. “It all started with the question, are these tardigrades alive?” says astrobiologist Alejandra Traspas Muiña, co-author of the study published in the journal Astrobiology.
During his research he tested the resistance of tardigrades to impacts. These were able to survive shocks of up to about 825 m / s, but not higher, as they exploded. This could mean that despite their ability to survive in the vacuum of space, these small animals would be unable to withstand a forced landing on another planet from a meteorite.
To do this, the researchers frozen tardigrades of the species Hypsibius dujardini and put them inside nylon bullets to fire them at various speeds, between 550 and 1000 m / s against sandbags that were intended to mimic the lunar surface. Something curious is that, while the tardigrades of the control group, that is, those not shot, it took about nine hours to thaw and recover; For the specimens that managed to survive the impacts, it took about 36 hours to return to their normal vital conditions. Noting that the impact, even if it does not end with them, has an adverse effect on these small animals.
Samuel Halim, a planetary scientist at the University of London, who is not involved in the work, says that the fact that tardigrades could not possibly survive impact against the lunar surface puts limits on the theory of panspermia, in which different organisms they could jump between planets in the solar system, colonizing and expanding. This could be one of the possible beginnings of life on Earth.
Astrobiologist Alejandra Traspas Muiña, on the other hand, does not lose hope and indicates that if the tardigrades fell on the water they could have a softer landing. “It is difficult for tardigrades to survive panspermia in the solar system, but it could happen,” he adds.
References:
Traspas, A., & Burchell, M. J. (2021). Tardigrade Survival Limits in High-Speed Impacts—Implications for Panspermia and Collection of Samples from Plumes Emitted by Ice Worlds. Astrobiology. Published. https://doi.org/10.1089/ast.2020.2405
