BREMEN, GERMANY - JULY 21:  Engineer Daniel Schubert (left) and student apprentice Alexander Bell (right) talks to each other in a laboratory at the German Aerospace Center on July 21, 2014 in Bremen, Germany. Scientists and engineers from the German Aerospace Center (DLR) are developing greenhouses for a potential Mars colony. The greenhouses will contain combined life-support systems which use recycled urine to manufacture fertilizer, helping to grow vegetables for a lunar and Mars environment. The first greenhouse will be tested for nine months in 2016/17 in an inhospitable environment in the Antarctic.  (Photo by David Hecker/Getty Images)