Cancer Mystery

Researchers agree that space radiation can cause cancer. They're just not sure how.

Despite urgent warnings from Hollywood, double-jawed aliens are probably not a spacefarer's biggest risk. Radiation is worse. It shreds not flesh, but DNA molecules, and that can cause a multitude of problems. One big one: it can lead to cancer.

Oddly enough, according to cancer specialist Dr. John Dicello of the John Hopkins University School of Medicine, radiation "is relatively poor at inducing cancer." Chemicals, he says, can do far more damage, as shown by the strong tie between environmental contaminants and increased levels of cancer.

Out from under Earth's atmosphere, astronauts are exposed to space radiation

But for space travellers, radiation is a tremendous worry. That's because astronauts are exposed to far more radiation than we typically encounter on Earth. And it's a different kind of radiation. Cosmic rays from deep space, for instance, are composed of heavier particles than our bodies are used to, and they have little trouble breaking strands of DNA.

Broken DNA, by itself, is not necessarily cause for alarm. DNA strands break all the time. Even a physical blow will do it. "If you hit yourself with a hammer," notes Dicello, "that can do a lot more damage than most radiation exposures." Because this kind of damage occurs so frequently, the body has evolved mechanisms to handle it.

Sometimes, he explains, cells with damaged DNA simply destroy themselves. Other times, they try to repair the damage. Problems start when they do this incorrectly. They might, for example, insert a chunk of DNA in the wrong place. Or they might attach it to the wrong chromosome.

Space radiation damages DNA.

When that happens, it's possible that the mistake will let that cell ignore constraints designed to make cells behave. A cancer can start when altered genes allow the cell and its descendants to multiply too freely.