Mystery dark spot on Enceladus intrigues scientists

View larger. | The Cassini spacecraft caught this view of the surface of Enceladus, a moon of Saturn, in 2008. Now, in a new study, researchers have announced an unusual dark spot on Enceladus (the image superimposed in the upper left). The spot disappeared over a period of about 3 years. What was it? Image via NASA/ JPL-Caltech.

• Saturn’s moon Enceladus has a bright surface of ice above an inner ocean. Recently, scientists noticed an odd dark reddish-brown spot on this surface in old spacecraft images.