Living in zero gravity during the Earth-Mars transit will have some pretty harsh side effects, but most urgently they'll have to readjust to gravity again. And those first few days on Mars will be busy as the first Mars explorers get their bearings, prepare their habitat for the stay and begin thinking about setting up experiments.

You can therefore see why NASA is so intent on figuring out how to help astronauts stay healthy and happy after long stays in space so they can adjust quickly for life on Mars. We already know that a six-month stay on the International Space Station wreaks havoc with bone and muscles, but at least when the space station crew return to Earth they have a team of medical professionals to look after them. The first Mars astronauts will have no such luxury.

Now, a new "bed rest" study detailed in the journal NeuroImage suggests that astronauts could also see changes in the brain, although it has yet to be proven in flight. For bed rest studies, brave volunteers agree to spend weeks or months in a head-down position at a facility in Texas to simulate the effects of zero-gravity. While the pay is pretty sweet for lying in bed — one study paid $18,000 for 70 days in a prone position — one volunteer said that it was hard to stay upbeat amid the isolation.

Rachel Seidler, of The University of Michigan and principal investigator of the study, noted that in some cases the bed rest group and the control group showed little change between them. A rotation test, for example, where the participants mentally rotate objects to find their correct orientation, showed that both groups got better with time. The bed rest group actually improved more as a whole when compared with the control group, she said, but it was likely because they were assessed more frequently and therefore had more practice.

Read the full article "Trip to Mars Could Throw Off Astronauts' Balance" at