Radiation. It’s everywhere, from the fallout of nuclear weapons to medical X-rays. It’s a cause of cancer, but it’s also one of the preferred forms of cancer treatment. There’s also a lot of it in space, and if we want to send astronauts to Mars safely, that’s a problem.
The charged particles commonly called radiation are a serious threat to anyone traveling in space, whether it’s a stay on the International Space Station or beyond. The Earth’s magnetic field protects people on the planet from radiation by trapping the particles in radiation belts that surround the globe. These doughnut-shaped areas in space, called Van Allen belts, lie up to 36,000 miles from the Earth’s surface. Within Earth’s orbit, astronauts are protected, but you can’t get to the moon, Mars or beyond without venturing past them. Once astronauts travel through and beyond the Van Allen belts—hazards in and of themselves because they trap these harmful particles—their bodies become vulnerable.
Deep space astronauts have to contend with two types of radiation. The first is composed of galactic cosmic rays, high-energy particles that travel at close to the speed of light. These cosmic rays, which are mostly protons but can also be composed of heavier elements, can damage human DNA, trigger mutations and change gene transcription. When gene transcription occurs, DNA produces RNA, which carries the instructions from DNA to the cells in the body. When that process is changed, RNA carries imperfect instructions to the cells. Over the medium and long term, these errors can become permanent mutations.
It seems inevitable that humans are going to Mars, so both public and private companies are testing and retesting every aspect of that journey. But unless they figure out the radiation problem, all that preparation will be moot.
Scientists at the Wake Forest Institute for Regenerative Medicine just wrapped up a NASA-funded study that examines the effects radiation from a Mars mission might have on astronauts. The team focused on the hematopoietic system, which is primarily composed of bone marrow, the spleen, the thymus and lymph nodes. “We know from studies on the atomic bomb survivors that the hematopoietic system is one of the more sensitive tissues in the body to the effects of radiation,” says Christopher Porada of Wake Forest University, a senior researcher on the project. Leukemia, unlike many other types of cancer, can develop quickly. “It would actually compromise both the mission and the astronauts’ health during that two-year period of time,” Porada says.
Galactic cosmic rays have a low radiation dose rate; during shorter trips, it’s not as serious an issue. “Going to the moon, astronauts received very minimal radiation,” Porada says. But its cumulative effect means that during a longer Mars mission (a minimum of two years, round trip), radiation is a much larger and more present threat.
But the news isn’t all bleak: The same team posits that a daily oral vitamin might be able to protect astronauts from space radiation’s harmful effects. “We’ve found a dietary supplement that appears to restore about 75 percent of the potential of the cells, if we put them on the cells before we expose them to the radiation,” says Porada. The pill isn’t absorbed well orally, so the team is working on a way to improve the supplement’s solubility.
If we can’t protect from within, how about from without? StemRad, an Israeli company based in Tel Aviv, specializes in radiation protection for nuclear workers and first responders. Now it has designed a vest that will protect astronauts from space radiation. Organs, tissues and stem cells are particularly vulnerable to radiation, and the vest was designed to specifically shield those delicate areas. The vests come with a pretty big caveat: Astronauts would have to wear them around the clock. StemRad’s aim is to tailor each vest to each astronaut for maximum comfort and flexibility.
The company announced on March 3 that the vest will be on Exploration Mission-1, the unmanned test of NASA’s new space vehicle Orion, currently scheduled for a late 2018 launch. Two dummies will fly aboard the capsule on its circumlunar flight. Only one dummy will wear StemRad’s vest. Upon their recovery, NASA will perform tests on both dummies to determine the effectiveness of the vests’ radiation protection. (It’s also possible NASA will decide to put a human crew on EM-1; it is conducting a feasibility study. No word on whether a human would don the vest.)
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Unfortunately, there’s a second type of radiation NASA needs to worry about: solar radiation. “Solar proton events, or solar particle events, are energetic particles that are emitted by the sun,” says Elsayed Talaat, a discipline scientist in NASA’s heliophysics division. Particles discharged by space weather events, such as solar flares, can affect astronauts acutely in the short term, damaging the central nervous system and resulting in impaired motor function and cognitive function. In the long term, these particles increase their cancer risk.
NASA is testing various methods to protect Mars astronauts from solar radiation. The Orion spacecraft will be equipped with radiation sensors, the crew will be notified if a solar flare or other radiation event occurs, and the crew will have time—between 30 minutes and a few hours—to take shelter in the spacecraft’s cargo area, protecting themselves from the bulk of the radiation.
But what if scientists could predict these explosions and whether one would trigger a radiation event? “Our ultimate goal is predictability of these space weather effects,” says Talaat. “That is hopefully the endgame of physical understanding, if you’re able to predict the phenomena.”
It’s clear that the answer to protecting astronauts from space radiation lies in a balancing act: outer versus inner, prediction versus protection. Regardless of how NASA does it, the radiation problem is one we need to solve. Otherwise, we’re looking at a long future of going nowhere at all.
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