Snapshots From the Meeting

the intensity of reflected sunlight. Cassini scientist Robert M. Nelson of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, and other members of the Visible and Infrared Mapping Spectrometer team reported their analyses of light reflected at various angles from two dark, circular features that looked like possible impact craters 1000 kilometers across and from a similarly sized but irregularly shaped dark feature. The three dark regions seemed likely places for hypothesized methane rains to collect, but Nelson’s analysis found nothing that indicated pools of liquid. Brightness variations across the three features were too large to be coming from liquid surfaces or even varying topography. They only made sense as variations in surface reflectivity. Apparently, the two circular features are not depressions but perhaps ancient impact scars that are now filled in. There’s “no evidence whatsoever to suggest there are accumulations of liquid of any form,” says Nelson. The search for liquids on Titan is not over, however. Their nondetection has “certainly been a surprise,” said Cassini project scientist Dennis Matson of JPL, but “we’ve only seen a part of Titan to this stage.” Nelson allows that small lakes might yet be found. The liquid methane might even be hiding beneath the surface like groundwater. If so, the Huygens probe scheduled to parachute to the Titan surface on 15 January would arrive with a thudding jolt rather than a splash.