Microbes Could Survive an Asteroid Impact and Hitchhike on Debris Between Planets, Including Mars and Earth

When a massive asteroid hits a planet, its impact can fling chunks of rock into space at incredible speeds. Some of these fragments could eventually land on other worlds, including Earth. But could anything living survive this violent journey?

New research suggests the answer might be yes. In experiments designed to mimic the extreme forces of a planetary impact, researchers found that a bacteria known to be resilient could withstand pressures similar to those experienced by rocks thrown off the coast of Mars by an asteroid strike.

The results, published in Nexus PNASadd new support to the idea that life could move between planets.

“Life could actually survive by being ejected from one planet and moving to another,” lead author KT Ramesh said in a press release. “This is a very big problem that changes the way you think about the question of how life begins and how life began on Earth.”

Can microbes survive asteroid impacts?

Researchers wondered whether microscopic life could withstand the violent forces produced when an asteroid hits a planet. Such impacts generate immense shock pressures that could potentially destroy the fragile organisms trapped in the rock fragments.

If microbes could survive these conditions, it would support a hypothesis known as lithopanspermia – the possibility that life could move naturally between planets aboard impact debris.

Previous studies have tested this theory, but many have relied on common terrestrial microbes that are not particularly adapted to extreme environments.

To explore the question more realistically, the team designed an experiment that recreated the immense pressures a microbe might experience when thrown off a planet during an asteroid strike.

Learn more: Recycled human waste could help produce food on the Moon and Mars

Gas gun test simulates asteroid impact

The selected team Deinococcus radioduransa desert bacteria famous for its ability to withstand brutal conditions such as intense radiation, freezing temperatures and extreme drought.

To simulate the shock of an impact, the researchers sandwiched the microbes between metal plates and fired a projectile at them using a gas gun. The impact generated pressures of between 1 and 3 gigapascals. As a reminder, the deepest part of the ocean experiences pressures of around 0.1 gigapascal.

“We expected it to have died at that first squeeze,” said lead author Lily Zhao. “We started shooting at him faster and faster. We kept trying to kill him, but he was really hard to kill.”

At around 1.4 gigapascals, almost all of the bacteria survived. Even at 2.4 gigapascals, about 60 percent of the cells were still alive.

In fact, the experiment found that the bacteria were so resistant that the testing equipment failed before the microbes.

Asteroid debris could carry life between planets

Asteroid impacts on Mars can generate pressures of around 5 gigapascals, although some fragments experience much less. The fact that bacteria survived pressures approaching these levels suggests that microbes buried in rocks could survive after being expelled from a planet.

“We showed that it is possible for life to survive large-scale impact and ejection,” Zhao said. “This means that life can potentially move between planets. Maybe we are Martians!”

The results also raise important questions for space exploration. If microbes can survive violent planetary impacts, they might also survive spacecraft travel. This possibility has implications for planetary protection – policies designed to prevent terrestrial microbes from contaminating other planets or extraterrestrial organisms from reaching Earth.

The researchers note that Mars’ moon Phobos, which orbits very close to the planet, could be particularly vulnerable to contamination because debris ejected from Mars could reach it with much less pressure than material traveling to Earth.

Future studies will test whether repeated asteroid impacts could make microbes even more resilient and whether other organisms, including fungi, could survive in similar conditions.

Learn more: No bacteria have been found on Mars: could they be below the surface?

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