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Cosmic Rays and Twisted Genes: How Space Messes with Astronaut DNA

Solo astronaut floating in space with a black background speckled with pink, green, and blue colour with stars.

Written by Isabella Schick
Illustrated by Alba Villatoro

Space is more than just an adventure; it challenges the very fabric of human biology. Beyond the protective haven of Earth’s atmosphere, astronauts are exposed to intense radiation that can alter DNA in ways we are only beginning to understand. These high-energy cosmic rays do not merely pass through the body unnoticed; they leave a lasting impact on the genetic code, raising concerns about long-term health and the future of human space travel.

Earth’s atmosphere serves as a natural shield, absorbing much of the radiation from the Sun and deep space before it reaches the surface. However, in outer space, astronauts face a harsher reality. Galactic cosmic rays (GCRs) and bursts of solar radiation bombard their bodies at nearly 200 times the levels experienced on Earth. These high-energy particles penetrate cells at nearly the speed of light, ionizing molecules and generating reactive species that can break chemical bonds, leading to cellular and genetic damage.

DNA carries the blueprint for life, and radiation in space can disrupt this delicate code. When GCRs strike, they ionize atoms within DNA molecules, leading to strand breaks and mutations. The effects of this damage can be likened to entire sentences being erased or rearranged in a book. While some sections of the DNA may remain intact, others become unreadable or entirely nonsensical.

Radiation affects DNA at multiple levels, but some types of damage are more severe than others. Double-strand breaks are particularly concerning because they affect both strands of the DNA helix, making accurate repair much more difficult. If the body’s repair mechanisms fail to restore them correctly, mutations can arise, potentially leading to cancer, accelerated aging, or inherited genetic changes. There is even speculation that prolonged space travel could permanently alter astronauts’ DNA, affecting not only their own health but also that of future generations.

Arrow points from a double-stranded helix strand to another splitting stranded helix strand getting hit with GCRs. One last arrow points to another double-stranded helix strand that has been mutated and some information of the helix has been deleted.

To better understand space’s effects on human genetics, NASA conducted an unprecedented experiment using identical twins. In 2015, NASA conducted a groundbreaking experiment using twin astronauts Mark and Scott Kelly. Scott spent nearly a year in space, while Mark remained on Earth as a control subject. Upon Scott’s return, researchers compared his DNA to Mark’s and discovered that his telomeres (the protective caps at the ends of chromosomes that prevent deterioration) had lengthened in space but rapidly shortened upon his return. Since telomere length is associated with aging and cellular health, these unexpected results raised new questions about the effects of spaceflight on biological aging and cellular stability.

With the risks of DNA damage established, scientists are now racing to develop strategies for protecting astronauts. Protecting astronauts from radiation remains a top priority for space agencies. Scientists are exploring various strategies to mitigate DNA damage, including radiation-blocking materials, which absorb or deflect harmful particles, and underground habitats on Mars that could provide natural shielding from cosmic radiation. Pharmaceuticals designed to enhance cellular repair mechanisms are also being studied. Additionally, genetic tools such as gene editing are being explored to make human cells more resistant to radiation by enhancing DNA repair pathways. While this concept may seem like science fiction, it is being seriously considered as a way to prepare humans for deep-space missions.

As humanity sets its sights on interplanetary travel, understanding the impact of radiation on DNA remains one of our greatest biological challenges. Could we one day engineer radiation-resistant humans? Can we develop technologies that mimic Earth’s protective atmosphere? The answers to these questions may shape the future of space exploration and even influence the trajectory of human evolution. One thing is certain: space is not just a physical journey but a test of human resilience, down to the molecular level.

Sources:

  1. Space Radiation Risks. NASA; 2024 Oct 22. [accessed 2025 Feb 16]. https://www.nasa.gov/hrp/radiation/space-radiation-risks/
  2.  Chromosomal positioning and epigenetic architecture influence DNA methylation patterns triggered by galactic cosmic radiation. PubMed; 2025 Jan 15. [accessed 2025 Feb 17]. https://pubmed.ncbi.nlm.nih.gov/38225252
  3. NASA’s Twins Study Results Published. NASA; 2019 Apr 11. [accessed 2025 Feb 16]. https://www.nasa.gov/humans-in-space/twins-study/

4. Telomeres, lifestyle, cancer, and aging. PubMed; 2011 Jan. [accessed 2025 Feb 17]. https://pmc.ncbi.nlm.nih.gov/articles/PMC3370421

5. The National Academies of Sciences, Engineering and Medicine. Space Radiation and Astronaut Health: Managing and Communicating Cancer Risks. Washington (DC): The National Academies Press; 2021. p. 33 – 50. [accessed 2025 Feb 16]. https://nap.nationalacademies.org/read/26155/chapter/4

6. Radiation. NASA; 2025. [accessed 2024 Oct 24]. https://www.newscientist.com/article/mg26435140-700-solving-stephen-hawkings-black-hole-paradox-has-raised-new-mysteries/ 

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