By comparison with spectra of various ices that could exist on Titan, it is found that methane ice could account for the bright area observed. Scientists are investigating the possibility for the presence of methane ice on Titan's surface at the equator, on top of a mountain, or at higher latitudes, where the temperature is expected to be lower than at the equator. Top image is J-band and bottom is H-band.

Some of the best images ever obtained by a ground-based telescope of Saturn's mysterious moon Titan will be presented by Dr. Athena Coustenis of the Paris-Meudon Observatory, France, at the General Assembly of the International Astronomical Union on next Tuesday. The new infrared images, obtained with the 3.6-metre Canada-France-Hawaii Telescope (CFHT) in Hawaii, confirm earlier observations showing that there is a brightly reflecting area in the equatorial zone extending over about 50 degrees of longitude. There are at least three individual bright features within this area.

Dr. Coustenis and her colleagues say that frozen methane could account for the observed bright region. One possible explanation is an ice-covered mountainous plateau. They are investigating theoretically whether methane ice could exist at high altitudes in Titan's equatorial regions, or at higher latitudes, where the temperature is lower than near the equator.

Titan's surface cannot be seen in the normal way, because of chemical haze in its thick nitrogen atmosphere. Although ordinary light cannot penetrate the haze, infrared radiation can. Measurements at different infrared wavelengths reveal information about various levels in Titan's atmosphere and its surface below. In computer processing, the contribution from the atmosphere is assessed and subtracted to leave an image of the surface alone.

Photometry processes and more data are required to complete the analysis of Titan's surface spectrum and to infer information on the morphology and the constituents on the ground. Understanding the nature of Titan's surface will provide major clues for understanding the prebiotic chemistry processes in a primitive planetary atmosphere.

These new images of Titan's surface show its appearance at wavelengths of 1.3 and 1.6 microns. Their exceptional quality is due to excellent observing conditions and a new adaptive optics system on the CFHT, which compensates for the blurring effect of moving air in Earth's atmosphere.

Titan is of special interest because it is the only moon in the solar system with a thick atmosphere. A little larger than the planet Mercury, it is the second largest moon in the solar system. The atmosphere is almost entirely nitrogen and about half as thick again as Earth's atmosphere. Astronomers have suspected that Titan's surface may have lakes or oceans of liquid hydrocarbons, but the new insights offer even more exotic and complex possibilities: ices, rocks, organics, etc. Titan is the target of the Huygens probe due to arrive in 2004 as part of the NASA/ESA Cassini-Huygens mission to Saturn and its moons.