„Maybe we are from Mars“: Microbes can survive transport through space

Microorganisms can survive the extreme pressure of an asteroid impact, be ejected into space, and then bridge the journey to another planet. This is the conclusion of a US research team based on an experiment on the resilience of a particularly robust bacterium from the Chilean desert. To achieve this, they placed Deinococcus radiodurans between metal plates, which they then shot with a gas gun. This simulated the exact conditions that are likely to prevail during an asteroid impact on Mars, for example. Surprisingly, the bacteria even survived the experiment better than the equipment, which broke apart. According to the researchers, this supports a hypothesis about the spread of life called lithopanspermia.

“Life forms could actually survive being ejected from one planet and moving to another,” summarizes engineer K.T. Ramesh: “This is a really big deal that changes the way you think about the question of the origin of life and how life began on Earth.” It would therefore be conceivable that life once originated on Mars and was transported to Earth by asteroids. At the same time, the team also believes that the finding should lead to a revision of the rules designed to prevent contamination during the transport of extraterrestrial samples to Earth.

“Really hard to kill”

The research group now explains that they wanted to find out with the experiment at what pressure two metal plates must be pressed together so that microbes trapped between them die. For this purpose, a projectile was shot at the research setup at almost 500 km/h, generating a pressure of 1 to 3 gigapascals in between. This is ten times more than the pressure at the bottom of the Mariana Trench, the deepest point in the Earth's oceans, and yet the bacteria survived. Only at the highest pressure were damages to the microorganisms observed. Nevertheless, more than half survived: “We kept trying to kill it, but it was really hard to kill,” says lead author Lily Zhao.

At the same time, the team also explains that an impact pressure of 5 gigapascals and more can be reached during asteroid impacts on Mars. This is more than in the experiment. Nevertheless, they are sure that at least some particularly resilient bacteria could survive this. Their experiment shows that this is possible: “What that means is that life can potentially move between planets. Maybe we're Martians!” says Zhao. Next, the research team wants to test whether other organisms, especially fungi, could possibly survive these conditions. They also want to find out whether more resilient populations of organisms can emerge through such events. Their current work was published in the journal PNAS Nexus.

(mho)