Spaceflight Accelerates Human Aging, Study Finds

Scientists working with NASA have discovered evidence that human stem cells undergo accelerated aging when exposed to the rigors of spaceflight. The main culprits seem to be microgravity and cosmic radiation, but the implication is clear: The human body isn't particularly well-suited to the universe beyond our home planet.

So, what could this mean for future long-term crewed missions—and even permanent settlement on the Moon or Mars?

Age is a tough thing to define by anything other than the passage of time. What does it mean to "accelerate aging" without actually changing the speed of that flow? In general, biology has settled on a few basic attributes of a cell to quantify its age level. One is the strength and quickness of immune function and the cell's ability to deal with stressors in general. Another is the length and condition of the end-caps on chromosomes, known as ...