Can humans evolve to make space travel safer?

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Near the cement-sealed Chernobyl nuclear power plant, site of the worst nuclear accident in history, you might expect a wasteland—a stretch of Ukrainian countryside completely uninhabitable by organisms of any kind.

But you’d be wrong. Wolves hunt their prey. Owls soar overhead. Somehow, nature is persevering.

How this is happening isn’t entirely clear, because we know that radiation is a significant mutagen that can have adverse effects on life forms. In April of 1986, Chernobyl released immense amounts of radiation into the surrounding environment. Though humans still don’t live there due to the dangers of radioactivity, wildlife has remained in the region, which has prompted scientists to ask if these animals are evolving to withstand the high amounts of radiation [1].

The phenomenon isn’t just interesting here on Earth—it’s also interesting for the possible implications it has on space travel. Besides emitting light, stars bathe the universe in particle radiation with periodic bursts from solar explosions [2]. Humans have big ambitions to go to Mars and beyond. Like the wildlife surrounding Chernobyl, humans will have to learn how to live in a radioactive environment if we want to go to Mars. So, as we venture into the new frontier, how will we stay safe? Could our DNA evolve to help us?

Stars bathe the universe in particle radiation

DNA is one of the big reasons that radiation is dangerous for us. When assembled into the right order, DNA is like an instruction manual for how to build life. Naturally, it’s important to try and protect the DNA and prevent it from being damaged. Just like ripping pages out of a book, it would be bad for a cell to have its DNA broken—which is exactly what radiation can do. Radioactive particles penetrate into a cell and collide into the DNA and other molecules with large amounts of energy. This powerful collision breaks chemical bonds and can cause multiple types of DNA damage. Luckily, most organisms have evolved elaborate mechanisms to repair damaged DNA. Depending on the type of damage, a cell can rewrite the portions of DNA that were broken, or fix it in other ways that are somewhat similar to taping a torn page in a book.

These repair mechanisms are extremely effective, but they can sometimes lead to mutations. In the book analogy, this would be like rewriting a torn page and accidentally adding in a typo. Mutations may be harmless, or they could cause a cell to behave erratically and lead to disease. For this reason, when there is too much damage in a cell, they will trigger a safety measure that causes the cell to die and prevent potential disease development.

Some organisms have evolved an incredible ability to survive radiation induced DNA damage

Studies of plants and animals in the Chernobyl region have shown significant increases in the amount of DNA damage in some animals, and there are many indications of a higher mutation rate among them [1,3,4]. Yet, they’re still able to survive. It’s been suggested that they’ve begun to evolve more efficient mechanisms for coping with the DNA damage, but research is ongoing.

Elsewhere, there are examples where organisms have evolved an incredible ability to survive radiation induced DNA damage. The bacteria Deinococcus radiodurans is famously able to survive extreme levels of radiation without dying, and is even able to preserve its DNA sequence relatively well [5,6]. How it does this is not entirely clear, because it has many of the same DNA repair genes as humans do. But scientists are very interested in learning more about how this bacteria has adapted to live under such extreme conditions. Understanding how an organism survives radiation could influence how we approach radiation protection for ourselves.

Life can flourish under high levels of radiation

So it appears that life can flourish under high levels of radiation, but it requires a coping mechanism to allow survival despite DNA damage and mutation. For the most part, radiation from space isn’t a problem for us because the earth is surrounded by a magnetic field that prevents the radioactive particles from reaching us [2]. However, such a field is not present around Mars, and it’s likely that any human colony living there will be exposed to continuous radiation at rates much higher than here on Earth.

Astronauts have been going to space for decades but have mostly remained within the magnetosphere. By staying within its protection—and by limiting the length of time astronauts spend in space—these temporary space travelers have been shielded from the more extreme radiation exposure that would be experienced on a longer (or permanent) trip, like heading to Mars. Ongoing studies aim to determine if our body is capable of repairing DNA damage incurred during space travel and how our body may or may not cope with it [2]. Studies in which astronaut Scott Kelly went to space for nearly a year aboard the ISS while his twin brother remained on Earth as a control provided evidence that the human body may increase expression of DNA damage repair genes to help protect our DNA in space, but further studies are needed to both confirm these results and understand their implications.

So, all of this brings us back to the main question: will our DNA evolve and come to our rescue as we establish homes on Mars? Life is always evolving, so there’s no question that humans will continue to do so. But it’s not clear yet whether the amount of radiation in space could affect us in such a way as to influence our evolution. Additionally, evolution takes place on a very large time scale, so it would take thousands of years for this to happen (at minimum). That’s not to say we won’t get to Mars before that—but to do it safely, we’ll still need technology to shield us from the harsh effects of the final frontier.

References

1. Møller, Anders Pape, and Timothy A. Mousseau. “Strong Effects of Ionizing Radiation from Chernobyl on Mutation Rates.” Scientific Reports 5 (2015): 8363. PMC. Web. 1 May 2018.

2. Moreno-Villanueva, María et al. “Interplay of Space Radiation and Microgravity in DNA Damage and DNA Damage Response.” NPJ Microgravity 3 (2017): 14. PMC. Web. 1 May 2018.

3. Baker, Robert J. et al. “Elevated Mitochondrial Genome Variation after 50 Generations of Radiation Exposure in a Wild Rodent.” Evolutionary Applications 10.8 (2017): 784–791. PMC. Web. 2 May 2018.

4. Ragon, Marie et al. “Sunlight-Exposed Biofilm Microbial Communities Are Naturally Resistant to Chernobyl Ionizing-Radiation Levels.” Ed. Vishnu Chaturvedi. PLoS ONE 6.7 (2011): e21764. PMC. Web. 2 May 2018.

5. Makarova, Kira S. et al. “Genome of the Extremely Radiation-Resistant Bacterium Deinococcus Radiodurans Viewed from the Perspective of Comparative Genomics.” Microbiology and Molecular Biology Reviews 65.1 (2001): 44–79. PMC. Web. 2 May 2018.

6. Krisko, Anita, and Miroslav Radman. “Biology of Extreme Radiation Resistance: The Way of Deinococcus Radiodurans.” Cold Spring Harbor Perspectives in Biology 5.7 (2013): a012765. PMC. Web. 2 May 2018.