The smallest astronauts ever

The extremes of space are sufficient to rip the atmosphere off Mars (our is protected by our magnetic field!) – so what hope does a little bacterium have? Actually, it turns out, rather a lot.

Despite very low pressures and temperatures and direct exposure to ionising radiation, Deinococcus bacteria dumped on the outside of the International Space Station managed to survive there for three whole years^[1]! They’ve also been found to survive on and inside meteorites, and scientists are excited to find that they could be little interplanetary travellers – perhaps even explaining where life came from on Earth (yes! We might all be aliens!). This theory is known as panspermia.

 

Public Domain via Nadya_il (Pixabay)

However, after being brought back to earth, 96 in 100 of the bacteria died. Probing their DNA suggested they had been so exposed to radiation they were unable to grow or reproduce. The outer ones had been comprehensively fried, but some of the shielded bacteria were not dead to begin with. However, now so used to the extreme conditions of space, conditions on Earth were somewhat of a shock – too much of a shock, for most of them. Although only a few of the astronauts made it, 3 years is a long time, and scientists think that it may take up to 8 years before all of them died – longer if they were formed into bigger clumps.

So maybe panspermia shall remain just a theory. Or maybe microastronauts are our history.

To find out more about panspermia, check out our article on Mars!

References
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[1] Kawaguchi, Y., Shibuya, M., Kinoshita, I., Yatabe, J., Narumi, I., Shibata, H., ... & Yamagishi, A. (2020). DNA Damage and Survival Time Course of Deinococcal Cell Pellets During 3 Years of Exposure to Outer Space. Frontiers in microbiology, 11, 2050.