Originally published on March 31, 2014

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Results from a new NASA study conducted on a dozen astronauts show that the heart becomes more rounded when exposed to near-zero gravity for extended periods.

Facing eventual space travel to Mars, the study looked into how long-term space flight can affect astronauts' health.

On Earth, the heart's muscles work against the pull of the planet's gravity to pump blood to the brain and to other parts of the body.

The heart loses muscle mass when it doesn't work as hard in microgravity, NASA lead ultrasound scientist James Thomas M.D. said in a Science Daily report. "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."

Ultrasound imaging comparing astronauts' hearts before, during, and after space flights of 18 months or more shows that the heart becomes more spherical in space by a factor of 9.4%, a shift that was consistent with what the research team predicted using a mathematical model.

"The models predicted the changes we observed in the astronauts almost exactly," said Thomas. "It gives us confidence that we can move ahead and start using these models for more clinically important applications on Earth, such as to predict what happens to the heart under different stresses."

NASA scientists are now using the prediction model to study other heart diseases or when the heart is placed under stressful conditions.

When these astronauts return to earth after extended stays in outer space, they commonly pass out or become light headed in a condition known as orthostatic hypotension, where their hearts are unable to adapt to a sudden drop in blood pressure when standin