results back to earth. nasa has carefully selected the landing zone on mars in the gael crater where a huge mountain rises right out of the crater floor. scientists believe they see layers of sedimentary deposit here that they hope will help them understand more about mars' history but also what happened to the lakes and rivers. he's a mars expert at the university of colorado. the evidence this scientist says now seems clear that mars once had a very warm environment. >> perhaps even today. >> reporter: that possibility poses a big problem. nasa has gone to great lengths to ensure curiosity doesn't carry any earth germs that could contaminate life on mars. high resolution cameras have already detected what appear to be large ice sheets buried under the martian surface. curiosity's mission to determine whether life is or ever was buried there, too.