Lenticulae on Europa
Lenticulae on Europa The round, reddish spots in this image, each about 10 kilometers (6 miles) across, are named "lenticulae" (Latin for "freckles"). Generally, reddish features on Europa appear to be younger than the grayer or bluer features. Round features on planets that do not have an obvious impact origin are most often interpreted to be the result of upwelling of hot, less dense material to the surface. NASA / JPL / University of Arizona / University of Colorado

This image was composed of color data captured on June 28, 1996, overlaid on a high-resolution image captured on May 31, 1998.