There are many risks to be considered when sending someone into space, but no one ever predicted that an astronaut’s blood might genetically mutate as a result of leaving Earth. But this is exactly what researchers discovered when they examined the blood samples from 14 NASA astronauts who were active in missions between 1998 and 2001.

The blood samples, which were decades old, all showed a specific DNA mutation. Although they didn’t believe the mutations were serious enough to cause a major threat to the astronauts long term heath, it underlines the need for regular screenings, particularly for those heading off on longer missions in the future.

The mutation is caused by exposure to excess ultraviolet radiation and chemotherapy, and is known as Hematopoiesis, and shows a high proportion of blood cells from a single clone, compared to a normal blood sample. It seems possible that due to the length of exposure of astronauts to high levels of space radiation, the Hematopoiesis mutation is more likely, especially considering that every one of the blood sample tested from the astronauts showed exactly the same result. Hematopoiesis is similar to mutations we might normally see in older individuals, but in the samples taken, the median age of the astronauts was much younger at only 42.

David Goukassian, professor of medicine at the Icahn School of Medicine at Mount Sinai, explained that “astronauts work in an extreme environment where many factors can result in somatic mutations, most importantly space radiation, which means there is a risk that these mutations could develop into clonal hematopoiesis.”

With the prospect of heading to Mars in the future, or developing a potential colony on the moon, the expectation of longer exposure to space radiation is a hot topic for NASA, who have already made proposals to change the radiation limit that astronauts can be exposed to.  This latest study seems to add weight to this proposal.

Goukassian added that “the presence of these mutations does not necessarily mean that the astronauts will develop cardiovascular disease or cancer, but there is the risk that, over time, this could happen through ongoing and prolonged exposure to the extreme environment of deep space.”