Titan's Surface, Revealed by HST Imaging

Abstract

We present for the first time relative albedo maps of Titan's surface. The maps were made from images taken by the Hubble Space Telescope's planetary camera (295 km per pixel) through atmospheric windows at 940 and 1080 nm. Coverage at all longitudes and between 45°S and 60°N was obtained with 14 orbits from 4–18 October 1994. Each image is characterized by haze with both limb effects (brightening) and a large north–south contrast. Subtracting an averaged image from each frame removes haze effects and reveals surface features of ∼10% maximum contrast. Many features are clearly visible in multiple images and in both filters, but the surface map is dominated by a large, bright, roughly rectangular feature centered at 110°W, 10°S and elongated in an east–west direction (4000 × 2500 km2): this feature and others indicate the diversity of Titan's surface. We consider the origin of the bright feature in an otherwise dark landscape and suggest that highland washing by methane rainfall is a likely mechanism.