The Surface of Titan from NICMOS Observations with the Hubble Space Telescope

Abstract From diffraction-limited images produced by the near-IR camera NICMOS aboard the Hubble Space Telescope we derived maps of Titan's surface in the methane windows near 1.1, 1.6, and 2.0 μm. Each part of Titan's atmosphere and surface was imaged at least twice over a time period of 24 h to look for moving clouds. Despite careful analysis we found no evidence for cloud activity. On the contrary, we were able to reproduce most of the features identified by previous mapping efforts, indicating that the albedo landscape remained stable over several years and is most likely indigenous to the surface. At the 3σ level we confirmed two brightness peaks in the prominent, continent-sized bright feature on the leading side of Titan. Many smaller landmarks could be mapped, including distinct surface structures on the dark, trailing side of Titan. These rule out the presence of a single large ethane ocean on the “back-side” of Titan. No obvious differences could be seen between the maps at different wavelengths, other than a gradual loss of spatial resolution due to the diffraction limit of the 2.4-m primary mirror.