Bacteria survive asteroid-like impacts ^{CEFR B2}

Researchers report in PNAS Nexus that Deinococcus radiodurans, a desert bacterium from the high deserts of Chile, can survive impact pressures comparable to those produced when asteroids strike a planet and eject material into space. The microbe is notable for a thick shell and a strong ability to repair cellular damage, traits that likely helped it endure the tests led by senior author K.T. Ramesh.

In the experiments the team sandwiched bacterial samples between metal plates and struck them with a projectile fired by a gas gun at speeds up to 300 mph. Impacts produced pressures from about 1 to 3 gigapascals; for reference, the bottom of the Mariana Trench is around a tenth of a gigapascal. The bacteria survived nearly every test at 1.4 gigapascals and roughly 60% survived at 2.4 gigapascals. In one trial the steel holder that held the plates failed before the microbes died. In other high-pressure tests some cells showed ruptured membranes and internal damage.

The team notes that asteroid strikes on Mars may generate pressures perhaps close to 5 gigapascals, so the survival seen here—almost up to 3 gigapascals—supports the possibility of lithopanspermia, the transfer of life by rock. These results affect planetary protection and mission rules: Martian ejecta might reach nearby bodies such as Phobos with less pressure, so policies for avoiding contamination and handling returned material may need reassessment. The work was supported by NASA’s Planetary Protection program and reported by Johns Hopkins University. Next steps include testing whether repeated impacts produce hardier bacterial populations and whether other organisms, including fungi, can survive similar conditions.