NASA / SCIENCE PHOTO LIBRARY NASA / SCIENCE PHOTO LIBRARY
Mars. The distinct layering of this rock intrigued NASA scientists. They were interested in whether it was igneous or sedimentary. If the latter, then that may indicate that at one point in Mars' history water was present on the surface. Photographed by the Mars exploration rover Spirit in the Columbia Hills, Mars, in September 2004.
Model release not required. Property release not required.