“Extremophile” bacteria can survive asteroid impacts strong enough to launch them into space, a new lab experiment shows – suggesting that these space-rock crashes could spread any potential alien life between worlds.
In the new study, published March 3 in the journal PNAS Nexus, researchers squeezed Deinococcus radioduransa type of bacteria that has been shown to survive in space for years, between two steel plates. Then they squeezed the “sandwich” very hard and fast to simulate asteroids slammed into a planet, and measured how many of the microbes survived.
The sandwich presses were chosen based on what it would take for asteroids to hit March sending microbes and bits of the planet into space. The team tested pressures ranging from 1.4 to 2.9 gigapascals (GPa)—about 14,000 to 29,000 times the atmospheric pressure on Earth at sea level. About 60% of the microbes survived being hit with 2.4 GPa, and up to 95% survived when the pressure was lowered to 1.4 GPa.
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In most previous studies testing such scenarios, the survival rates of the microbes were orders of magnitude lower. The study authors theorized that this may be because the microbes tested in the new study were different: stronger; more resilient; and withstands extreme radiation exposure, desiccation (which becomes extremely desiccated) and high temperatures.
An extreme way of life
The researchers chose to test D. radio duration because it can withstand the cold, empty vacuum of space. ONE 2020 study found it D. radio duration survived to be exposed to space for three years while attached to the exterior of the International Space Station, which is not a friendly place for life. (Moss doesn’t seem to mindthough.)
The team also looked at how the microbes recovered from the impacts by incubating the cells at 98.6 degrees Fahrenheit (37 degrees Celsius) for a few hours and measuring which genes the microbes expressed. They found that, after being hit with higher-pressure impacts (hard enough to damage cell membranes), the microbes prioritized genes related to repairing cell damage rather than making new cells. They also ate more iron and repaired DNA.
An understanding of how life can move between planetary bodies is important for try-return missionnoted the study authors in the paper. For example, samples returned from Mars must undergo strict procedures to prevent possible Martian microbes from making a trip to Earth and possibly contaminating our planet. If asteroid impacts could transport microbes elsewhere in the solar system, samples returned from elsewhere may need additional precautions to prevent contamination as well.
Beyond that, the study shows that certain forms of life can survive being thrown violently into space. This can affect how and where we can look life in the solar system.
Kawaguchi, Y., Shibuya, M., Kinoshita, I., Yatabe, J., Narumi, I., Shibata, H., Hayashi, R., Fujiwara, D., Murano, Y., Hashimoto, H., Imai, E., Kodaira, S., Uchihori, Y., Yoga, Miko, K. & Yamagishi, A. (2020). DNA damage and survival time of deinococcus cell pellets during 3 years of space exposure. Frontiers in microbiology11, 2050. https://doi.org/10.3389/fmicb.2020.02050
