Danger Dust

Mars Missions May Be Blocked by Kidney Stones

In searching for potential dangers humans would face on a long Mars mission, scientists are leaving no stone unturned—including the ones that show up at weirdly high rates in astronauts’ kidneys.

Healthy kidneys filter blood to balance the body’s water, salts and minerals, expelling waste as urine. When this process goes awry, painful kidney stones—hard accumulations of salts and materials such as calcium—can form in this essential organ. Researchers have theorized that astronauts are prone to kidney stones because bones degrade faster in microgravity, increasing calcium levels in the blood. But these stones’ surprising frequency among space travelers even years after they return to Earth suggests other factors are involved.