Anyone dreaming of casting off the shackles of Earth for the microgravity wasteland of Mars is in for some (more) bad news. In addition to a host of other problems, the necessary 18-month spaceflight would, apparently, lead to one very unhealthy (and spherical) astronaut heart.

The new findings come from a recent NASA study in which 12 astronauts aboard the ISS took ultrasound images of their hearts before, during, and after their six-month stint in space. What they found confirmed scientists' previous prediction: In microgravity, the human heart becomes more spherical by a factor of nearly 10 percent. According to James Tomas, M.C., Moore Chair of Cardiovascular Imaging and Lead Scientist for Ultrasound at NASA:

The heart doesn't work as hard in space, which can cause a loss of muscle mass.
That can have serious consequences after the return to Earth, so we're looking into whether there are measures that can be taken to prevent or counteract that loss.

At least for the short amount of time ISS astronauts are in space, the heart condition seems to be only temporary; the participants' hearts returned to their longer, typical shape not long after returning to Earth. And though scientists know a more spherical heart likely means it's performing less efficiently, the long term cardiovascular effects of the change in shape have yet to be determined.


Stil, it's probably safe to assume that a circular heart doesn't mean anything great for the long run. That's not to say that Mars colonization is out of the question, but if we're ever going to get there in one piece, we're only just scratching the surface of what we'll be up against. [Science Blog]