Study finds microbes may survive asteroid blasts and travel between planets, reshaping life origin theories.
Microbes blasted off a planet by an asteroid strike may survive the journey to another world, including Earth, according to a new study from Johns Hopkins University .Researchers tested whether a hardy bacterium could endure the crushing pressures generated when a space rock slams into a planet and ejects debris into space.
The results suggest that life could survive the initial blast and potentially travel between planets embedded inside rock fragments.The idea, known as lithopanspermia, proposes that life can spread through space via meteorites and planetary debris. Scientists already know that Martian meteorites have landed on Earth. The question has been whether living organisms could endure the violent forces required to launch them off a planet in the first place.To find out, the team recreated the intense shock pressures associated with an asteroid impact on Mars and measured whether microbes could survive.Blasted off, still aliveThe researchers chose Deinococcus radiodurans, a bacterium known for surviving extreme radiation, cold, dryness, and other harsh conditions. It has a thick outer shell and strong DNA repair mechanisms, traits that could resemble hypothetical life on Mars.“We do not yet know if there is life on Mars, but if there is, it is likely to have similar abilities,” said senior author K.T. Ramesh.To simulate impact conditions, the team sandwiched the microbes between metal plates and fired a projectile at them using a gas gun. The projectile struck at speeds up to 300 mph, generating pressures between 1 and 3 gigapascals.For comparison, pressure at the bottom of the Mariana Trench is about 0.1 gigapascals. Even the lowest pressure in the experiment exceeded that by more than tenfold.The bacteria survived nearly all tests at 1.4 gigapascals and about 60 percent at 2.4 gigapascals. At lower pressures, the cells showed no visible damage. At higher pressures, some membranes ruptured, and internal structures were affected, but many microbes remained viable.“We expected it to be dead at that first pressure,” said lead author Lily Zhao. “We started shooting it faster and faster. We kept trying to kill it, but it was really hard to kill.”Rethinking planetary protectionWhen large asteroids strike Mars, some debris can experience pressures near 5 gigapascals, although not all fragments are subjected to the same forces. The new findings suggest that at least some microbes could survive a significant portion of that range.“We have shown that it is possible for life to survive large-scale impact and ejection,” Zhao said. “What that means is that life can potentially move between planets. Maybe we’re Martians!”The results could have implications for planetary protection policies. Space agencies impose strict contamination controls when sending spacecraft to Mars and when returning samples to Earth. However, Mars ejecta may also reach its moons, such as Phobos, under lower pressures than those required to escape to Earth.“We might need to be very careful about which planets we visit,” Ramesh said.The team plans to test whether repeated impacts could select for even hardier microbes and whether other organisms, including fungi, can survive similar shocks. The study was published in the journal PNAS Nexus.
Deinococcus Radiodurans Gigapascal Pressure Interplanetary Transfer Johns Hopkins University Lithopanspermia Mars Meteorites Planetary Protection
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