SAN FRANCISCO—NASA’s Cassini probe has snapped the first images of sunlight reflected off one of the hydrocarbon lakes at Saturn's moon Titan. Although the existence of liquid lakes there had already been confirmed by other means, this was a long-sought direct visual confirmation. Cassini scientists presented the images here Friday at a meeting of the American Geophysical Union.

"It was a little bit of luck," says Katrin Stephan of the German Aerospace Center in Berlin, who was the first person to spot the glint while browsing newly arrived infrared images. (Titan's atmosphere is too hazy for the lakes to be seen in the visible-light spectrum.) Cassini took the shots on July 8 from a distance of 200,000 kilometers, as it hurtled toward Titan for a flyby. Three out of four exposures taken within a three-hour period showed a beam of light on the edge of the moon. To rule out other potential phenomena, such as lightning or perhaps a volcanic eruption, Stephan and her collaborator checked that the alignment of the sun, Titan and the probe was just right for light to bounce off a lake. "It fit perfectly together," she says.