Scientists are hopeful that what they learn up in space will help millions of people at risk for osteoporosis on Earth.
On board the shuttle are 30 mice, currently floating in micro-gravity.
Half were treated with an experimental osteoporosis drug, half with a placebo.
The mice were sent up by a team of researchers led by the University of North Carolina's Dr. Ted Bateman, an expert in bone loss during space flight.
"Astronauts lose bone at a very rapid rate, at least five times the rate that women lose bone here on Earth," he explained.
That's because bones are designed to hold us up under the pressure of gravity on Earth.
In space, bones don't get the pressure they need to thrive, leading to a loss of bone mass.
Space exploration has been pivotal to osteoporosis research. Scientists studied microgravity's effects on bones and muscles since the 1970s.
It's the perfect environment for Bateman's latest research.
"Existing drugs stop the process of bone loss. This drug would hopefully build new bone and increase bone mass," he said.
Increasing bone mass would effectively reverse osteoporosis.
If accomplished it'd be yet another leap forward for the world of medicine.
The research team will study the mouse skeletons when they return to Earth and expects to have at least preliminary results sometime this fall.
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