Traveling deeper into space may carry some unanticipated health risks. Scientists have published a study noting that Apollo astronauts have died of heart disease at an unusually high rate — of the 7 that passed away during the study, 43 percent fell to cardiovascular conditions. Only 11 percent of those deceased astronauts who stopped at low Earth orbit succumbed to heart disease, which is about on par with the 9 percent rate on the ground. There’s a concern that the increased dose of radiation in deep space, however brief, is intense enough to mess with the functioning of cells that line blood vessels.
Before you ask: yes, the researchers are aware that the study is only covering a handful of people. It may take many more astronauts to reach a definitive conclusion. However, the outcome parallels what the team saw when subjecting mice to the same levels of radiation you’d get on a trip to the Moon. The irradiated rodents were disproportionately likely to suffer heart problems as they aged, just on a much shorter time scale.
This doesn’t mean that humans will have to stay near Earth to avoid a premature death. The findings challenge the all-clear message from earlier studies, though, and may give space agencies a reason for pause as they prepare for human travel to Mars. Spacecraft and spacesuits may need extra protection to ensure that crews lead long, healthy lives.