Water Bears Can Survive Impact Speeds of 1,845 Miles Per Hour

Tardigrades, also known as water bears, are hardy life forms that can survive extreme temperatures—from volcanic vents on the ocean floor to the frigid climes of Antarctica. The microscopic organism can also resist the vacuum of space and lethal doses of radiation, reports Jonathan O'Callaghan for Science.

To further test the water bear's survival limits, researchers loaded the microscopic beings into a gun and fired them at sand bag targets to test their impact survival rate, according to a study published in Astrobiology. It turns out, tardigrades can survive the violent impacts, but only to a certain point before they begin to fall apart. It could be the first step in exploring whether life can be distributed to other planets via asteroids—if the impact doesn't kill the lifeform first.

For years, scientists have speculated the possibility of panspermia, or microscopic lifeforms arriving from one planet to another via meteorites or comets, reports Becky Ferreira for Vice. Panspermia may potentially explain how life began on Earth. It could also determine whether a similar redistribution of life could happen by the same method on other hospitable planets.

In August 2019, Israel's lunar lander, Beresheet, crashed into the moon's surface while carrying thousands of tardigrades. Since then, researchers have wondered if the water bears survived the impact, reports Victor Tangermann for Futurism. With this event in mind, astrochemist Alejandra Traspas and astrophysicist Mark Burchell, who both work at the University of Kent, set out to find if the water bear's impact survival was possible.

They put the theory to the test by shooting tardigrades out of a lab-grade, two-stage, light-gas gun, which resembles a canon more than a gun. (A similar machine at NASA has a 24-foot-long "barrel" aimed at a target located 175 feet away. IT can shoot projectiles at speeds of 23,000 feet per second, or about four miles per second.) The "gun" in the study does use traditional gun powder and pressurized hydrogen or helium to fire at high speeds up to five miles per second, Futurism reports.

Before the experiment, the research team fed 20 freshwater tardigrades, Hypsibius dujardini, a diet of moss and mineral water before freezing them for two days, Science reports. Freezing the water bears places them into a "tun" state, sort of like hibernate. Once frozen, the microscopic organisms were placed into hollow nylon bullets and fired towards a sand target at velocities higher than a handgun can reach, Science reports.

Then, the water bears were collected from the target, poured into a water column, and observed to see how long it took them to wake from the hibernation state, reports Michelle Starr for Science Alert. Researchers found the bears could withstand an impact of up to 900 meters per second and shock pressures of up to 1.14 gigapascals. At higher speeds, the seemingly invincible water bears turned to mush.

The study results show that tardigrades can survive impact speeds of around 1,845 miles per hour. Still, meteorites that crash into other planets have higher shock pressures than those tested in the experiment, Vice reports, which means that tardigrades most likely won't survive an impact. However, some meteorites that hit Earth or Mars may experience lower shock pressures that a water bear could survive, Traspas explained to Science.​

While the findings didn't conclude if the water bears survived the crash on the moon, the study's researchers said their conclusions determine how researchers can safely collect lifeforms from other planets without turning them to mush like the water bears.

The study also explained how researchers might detect life during flybys of Saturn's moon Enceladus and Jupiter's moon Europa. Both moon's eject plumes of saltwater that may or may not contain lifeforms, Vice reports. Overall, researchers may be one step closer to finding how life began on Earth. All thanks to a gun that fires plump water bears.

Elizabeth Gamillo | | READ MORE

Elizabeth Gamillo is a daily correspondent for Smithsonian and a science journalist based in Milwaukee, Wisconsin. She has written for Science magazine as their 2018 AAAS Diverse Voices in Science Journalism Intern.