This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Deep space travel comes with a huge potential downside—radiation exposure that can kill an astronaut either quickly or slowly over time if not managed correctly. But what exactly does that mean, and is there any way to handle it other than sticking more and more protective layers between the squishy biological systems inside a spacecraft and the radiative void of deep space?
A new paper from researchers at Oklahoma State University and the University of Texas Health Science Center aims to answer both questions. While the sources of radiation they identify are complex, they also offer some potential solutions. Scientists have long known that one of the main causes of cancer in deep space travelers (and even airline pilots) is galactic cosmic rays (GCRs).
These are high-energy atomic nuclei that have been stripped of their electrons and accelerated by massive shock waves from supernovae. But they are typically stopped by the protective blanket of Earth's atmosphere before they can reach anyone on the ground. Astronauts in space are not so lucky, as they are subjected to high levels of GCRs, including the most dangerous kind—high-atomic-number, high-energy ions known as HZE ions, such as iron nuclei (Fe-56).
Iron ions are much more destructive than even X-rays, leaving a dense trail of ionization that literally rips through DNA strands and, with enough exposure, will almost certainly cause cancer. However, they are relatively rare. For a typical three-year round trip to Mars, calculations based on data from Curiosity's journey there suggest that only about 3% of an astronaut's cells would take a direct hit from an iron ion.
That doesn't sound terrible, given that it means 97% of a person's cells would avoid a direct hit. But flight surgeons are alarmed about what they call the radiation-induced bystander effect. To showcase this danger, the researchers gathered groups of human aortic endothelial cells—the kind that line the walls of blood vessels—and subjected them to Fe-56 ion beams at Brookhaven National Laboratory's NASA Space Radiation Laboratory.
In such conditions, it becomes readily apparent that cells directly hit by iron ions can't simply repair themselves or even die off. Instead, they start an inflammatory signaling cascade. After a cell is hit with an iron ion, it activates a transcription factor called NF-κB, which is crucial for inflammation and cellular defense.
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