When the Shuttle lifts off on July 1, the astronauts on board may well be concerned about their safety. But now they have something else to worry about: kidney stones. A University of Minnesota study revealed that astronauts may be at risk for developing kidney stones. The study simulated microgravity by having twins stay in bed for 30 days, except one of the twins exercised. The twin who didn't tended to have higher levels of calcium in their urine, a precursor to stones. I don't have access to the Journal of Urology, unfortunately, where the study was published (this is, in fact, the first time I have been upset I don't have access to the Journal of Urology). I'd like to read that article and see what's what. It sounds interesting, honestly, since I sometimes wonder what we don't know about long-term exposure to microgravity. We need to know this stuff before we go to Mars! And I wonder... what will it do to the human body when people live on the Moon, in 1/6th gravity? Our bodies have evolved in one gravity, and may not work properly in lower gravity over long periods of time. What else don't we know?