Microbes Could Survive an Asteroid Impact and Hitchhike on Debris Between Planets, Including Mars and Earth
When a massive asteroid slams into a planet, the impact can blast chunks of rock into space at incredible speeds. Some of those fragments can eventually land on other worlds, including Earth. But could anything alive survive that violent journey?
New research is saying the answer might be yes. In experiments designed to mimic the extreme forces of a planetary impact, researchers found that a famously resilient bacterium could withstand pressures similar to those experienced by rocks blasted off Mars by an asteroid strike.
The findings, published in PNAS Nexus, add new support to the idea that life could move between planets.
“Life might actually survive being ejected from one planet and moving to another,” said senior author K.T. Ramesh in a press release. “This is a really big deal 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 have wondered whether microscopic life could endure the violent forces produced when an asteroid strikes a planet. Such impacts generate immense shock pressures that could potentially destroy fragile organisms trapped inside rock fragments.
If microbes could survive those conditions, it would support a hypothesis known as lithopanspermia — the possibility that life might travel naturally between planets aboard impact debris.
Earlier studies tested this theory, but many relied on common Earth microbes that are not especially 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 blasted off a planet during an asteroid strike.
Read More: Recycled Human Waste Could Help Grow Food on the Moon and Mars
Gas Gun Test Simulates an Asteroid Impact
The team selected Deinococcus radiodurans, a desert bacterium famous for its ability to endure brutal conditions such as intense radiation, freezing temperatures, and extreme dryness.
Microbes before and after extreme impact.
(Image Credit: Johns Hopkins University)
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 between 1 and 3 gigapascals. For context, the deepest part of the ocean experiences pressures of about 0.1 gigapascal.
“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.”
At around 1.4 gigapascals, nearly all of the bacteria survived. Even at 2.4 gigapascals, about 60 percent of the cells were still alive.
In fact, the experiment revealed that the bacteria were so resilient that the test equipment failed before the microbes did.
Asteroid Debris Could Carry Life Between Planets
Asteroid impacts on Mars can generate pressures of around 5 gigapascals, though some fragments experience much less. The fact that the bacteria survived pressures approaching those levels suggests that microbes buried inside rocks might survive being blasted off a planet.
“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 findings also raise important questions for space exploration. If microbes can survive violent planetary impacts, they might also survive spacecraft journeys. That possibility has implications for planetary protection — the policies designed to prevent Earth 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, may be especially vulnerable to contamination because debris ejected from Mars could reach it with much less pressure than material traveling all the way to Earth.
Future studies will test whether repeated asteroid impacts might make microbes even more resilient, and whether other organisms, including fungi, could survive similar conditions.
Read More: Bacteria Haven’t Been Found On Mars — Could They Be Beneath the Surface?
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