Radiation is a key obstacle that we will encounter as we move towards long-duration missions. Where as to date we have been dealing with missions lasting up to 438 days (Soyuz TM-18), missions to other planets (e.g., Mars) will last years and take passengers through high radiation zones. Low dose-rate Galactic Cosmic radiation, consisting of protons, Gamma rays, high-energy heavy particles and secondary radiation, is known to cause neurological and cardiovascular deficits, along with cancer. Combined with the effects of microgravity, such radiation can cause permanent physiological damage. High dose-rate solar particle events, consisting of medium to high-energy particles, can cause acute radiation sickness. How heavily these symptoms will impact astronauts on long-duration missions is not yet fully understood.
The current countermeasures for radiation center around the resilience of the spacecraft and of the astronauts. Possible shielding for the spacecraft consists of passive and active shielding. While passive shielding consists of a layer of radiation-blocking material (preferably including high levels of hydrogen), active shielding utilizes magnetic fields, established around the spacecraft.
Radiation causes damage by creating free radicals and other reactive particles in the tissues of the body. There are a variety of countermeasures, applied to the human body, that can mitigate and prevent these effects. For instance, anti-oxidants can fight this damage by preventing oxidative damage from reactive molecules. Anti-oxidants can be found in Vitamin C, Vitamin E, Selenium, etc. Also, drugs such as Amifostine can be used to reduce the side effects of radiation. Other drugs, like Superoxide Dismutase can be used to prevent oxidative damage (though this drug is not thoroughly tested yet).
Astro-Omics offers a new approach to the dangers posed by radiation. By analyzing how the metabolic, genomic, and proteomic systems may react to radiation, Astro-Omics allows for the selection of the most resilient astronauts and the creation of personalized countermeasures. The analysis of DNA repair capabilities could allow researchers to identify those who do not have an adaptive response to radiation – the ability for DNA to repair itself after radiation damage is imperative. For instance, those with a one-carbon metabolism have a high concentration of uracil in cell nuclei, which can lead to breakage in DNA that can be hard to repair. Such a condition leads to unstable DNA that is more susceptible to radiation. Other conditions like mutations in DNA reparation, or low levels of Mg (which is involved in DNA reparation) would also be incompatible with the space environment. The most important part of analyzing these individualized conditions is deciding which rule out a candidate for a trek through space, and which simply call for an individualized treatment plan.
Here on Earth, we are seeing increasing signs that radiation effects are individualized. Recent studies have revealed that up to 80% of inter-individual radiation responses in normal tissue may be due to genetic factors. Research is leading us closer and closer to identifying the many genes involved in radiation responses. Such investigations will likely be furthered by space-based research into individual radiation responses. Thus, radiation research on Earth and in space will be key to understanding the individualized nature of the effects of radiation.
Along with this assessment of the factors affecting an individual’s resilience to radiation, Astro-Omics also includes the monitoring of an individual’s radiation exposure through biodosimetry. Biodosimetry uses biological markers of radiation exposure (e.g., chromosomal aberrations) to track the effects of radiation on an individual. Such a technique would allow us to understand how radiation affects a single individual and thus create a personalized treatment plan to mitigate effects and prevent future damage.
To learn more about space radiation, read up on the NASA website: http://srag-nt.jsc.nasa.gov/SpaceRadiation/What/What.cfm