May 11, 2010
The left-hand image, obtained by the European Space Agency’s Huygens probe, shows rounded rocks from the surface of Saturn’s moon Titan. Huygens rode with NASA’s Cassini spacecraft to the Saturn system. The right-hand image, taken by amateur photographer Sandra M. Matheson, shows river rocks on Earth.
Credit: NASA/JPL/ESA/University of Arizona and S.M. Matheson