As astronauts Butch Wilmore and Suni Williams get their land legs back on Earth, the effects of being stranded in space for nine months — and their recovery — will give scientists a chance to improve preparations for eventual, and even longer, space flights, say experts.NASA aims to send humans to Mars as early as the 2030s; flights which, there and back, could take 21 months. "The extreme environment of space, the radiation, the lack of gravity, even just those confined spaces, it can really take a toll on our health," said Dr. Farhan Asrar, associate dean of clinical faculty relations at Toronto Metropolitan University's medical school, who researches space medicine."Literally I would say pretty much from head to toe it can cause issues."Without gravity, bodily fluids shift upward, leadi...