Scientists Used Tardigrades as Bullets to See if They Can Survive Violent Impacts

Israel's lander Beresheet's crash-landing unleashed tardigrades onto the Moon. Could they have survived?
Derya Ozdemir

If there's an animal out there who is a better fit to perform Gloria Gaynor's I Will Survive, we are yet to know about it: From being boiled in alcohol to being blasted with radiation, tardigrades, often called water bears or moss piglets, can survive pretty much anything you throw at them, making them one of the most resilient animals known.

These tough and bizarre animals are nearly microscopic with long, plump bodies and scrunched-up heads that make them almost look adorable. They can be found virtually everywhere and can withstand practically most conditions

So when Israel's lunar lander Beresheet crash-landed in April 2019 and accidentally spilled thousands of tardigrades onto the Moon's surface, this sparked widespread speculations among scientists who pondered whether they might have survived the crash.

But how violent an impact could tardigrades survive? Astrochemist Alejandra Traspas and astrophysicist Mark Burchell from the University of Kent in the U.K. devised an experiment to find out, Science Magazine reports.

Scientists fired tardigrades out of a gun

The 20 tardigrades used in the experiments were fed moss and mineral water before being frozen for 48 hours to induce hibernation, a state known as "tun" in which their metabolism drops to 0.1 percent of their normal activity.

They were then put in a hollow nylon bullet two to four at a time. The scientists used a two-stage light gas pistol, a physics instrument that can reach muzzle velocities much higher than any traditional gun, to fire them at increasing speeds.

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The results, published in the journal Astrobiology, revealed that these tough creatures could survive impacts of up to 900 meters per second, and momentary shock pressures up to a limit of 1.14 gigapascals (GPa). However, above 901 meters per second, they turned into "mush."

This suggests that the tardigrades on Beresheet had a slim chance of survival, and the scientists "can confirm they didn't survive." Since the lander is believed to have crashed at a few hundred meters per second, Traspas estimates that the shock pressure produced by its metal frame hitting the surface would have been "way above" 1.14 GPa.

This means the tardigrades' toughness has its limits and puts restrictions on the panspermia theory, which argues that life could travel between worlds as stowaways on meteorites. Furthermore, the researchers argue that these findings could help decide how to maximize the chances of discovering life on Saturn’s moon Enceladus and Jupiter’s moon Europa

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