Scientists squished microbes into a steel ‘sandwich’ — and made a profound discovery about life in space
“Extremophile” bacteria could survive asteroid impacts strong enough to launch them into space, a new lab experiment shows – hinting that these space rock crashes could spread any potential extraterrestrial life between worlds.
In the new study, published March 3 in the journal Nexus PNAS, researchers sandwiched Deinococcus radioduransa type of bacteria that survives in space for years, between two steel plates. Then they crushed the sandwich very hard and very quickly to simulate asteroids hitting a planet and measured how many microbes survived.
Sandwich crush pressures were chosen based on what it would take for the asteroids to hit March to launch microbes and pieces of planet into space. The team tested pressures between 1.4 and 2.9 gigapascals (GPa), or about 14,000 to 29,000 times the atmospheric pressure on Earth at sea level. About 60% of the microbes survived at a pressure of 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, microbe survival rates were orders of magnitude lower. The study authors speculated that this might be because the microbes tested in the new study were different: stronger; more resistant; and capable of withstanding extreme exposure to radiation, desiccation (becoming extremely dried out), and high temperatures.
An extreme form of life
The researchers chose to test D. radiodurans because it can withstand the cold, empty void of space. A 2020 study found that D. radiodurans survived being exposed to space for three years while being tethered to the exterior of the International Space Station, which is not a friendly place for life. (This doesn’t seem to bother MossHowever.)
The team also examined how the microbes recovered after impacts by incubating the cells at 98.6 degrees Fahrenheit (37 degrees Celsius) for a few hours and measuring the genes expressed by the microbes. They found that after being hit by high-pressure impacts (hard enough to damage cell membranes), microbes prioritized genes related to repairing cellular damage over creating new cells. They also ate more iron and repaired their DNA.
It is important to understand how life might move between planetary bodies. sample return missionsthe study authors noted in the article. For example, samples returned from Mars must undergo rigorous procedures to prevent possible Martian microbes from hitching a ride to Earth and possibly contaminating our planet. If asteroid impacts could carry microbes elsewhere in the solar system, samples returned from other locations might also require additional precautions to avoid contamination.
Beyond that, the study shows that certain life forms can survive a violent shock in space. This may affect how and where we might search 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., Nakagawa, K., Mita, H., Yokobori, S., and Yamagishi, A. (2020). DNA damage and evolution of survival time of deinococcal cell pellets during 3 years of exposure to space. Frontiers of microbiology11, 2050. https://doi.org/10.3389/fmicb.2020.02050
