This image of the Taurus-Littrow valley shows the Apollo 17 landing site (the "+" symbol in the image). This region marks the last time - December 1972 - that humans walked and drove on the Moon's surface. Astronomers are using the Apollo 17 images (and those of the Apollo 15 site) as "ground-truth" in an effort to discriminate lunar materials enriched in ilmenite, a titanium-bearing oxide of potential value as a resource in human exploration of the Moon. Hubble's Advanced Camera for Surveys took the image on Aug. 16, 2005.