Assessing Cryovolcanic Resurfacing of Titan

Introduction: A quantitative assessment is made of " cryovolcanism " as a resurfacing process on the saturnian moon Titan. The geologically young surface of Titan indicates that much resurfacing has taken place. However, to date, there has been no unambigu-ous detection of active " cryovolcanism " , such as the emplacement of a " cryolava " flow. The dense Titan atmosphere makes this kind of observation very difficult. In addition, the Cassini nominal mission has fo-cused on mapping as much as possible of the Titan surface with SAR at ~300 m/pixel and optical instruments (ISS and VIMS) at ~10 km/pixel resolution. The detection of surface modification is hampered by a lack of repeat coverage by Cassini instruments at high spatial resolutions. Also, active areas may be very small and therefore difficult to detect. We are therefore modelling the thermal emission from a wide range of active and inactive cryolavas in order to determine process detectability as a function of eruption size. Observations: The case for currently ongoing volcanic activity on Titan is best made by citing the occurrence of some photometric variability seen in data from VIMS [1-3]. Other data obtained by VIMS [4-5] and, more recently, by the Cassini Radar [6] indicate that these sites are distinctively different from other landforms on Titan. Apparent albedo changes have been seen by VIMS in two locations, and at the first have been documented to be time-variable. It has been suggested that this brightening may be due to the deposition of surface frosts, or similar coatings, or possibly low-lying fog [1-3]. Voyager images of plumes on Io, Galileo observations of flow emplacement on Io, and Cassini observations of the plumes of Enceladus are all examples of conclusive evidence of endogenic volcanic activity in the outer solar system. But, for Titan, without any observations of eruptive processes in action, direct characterization of " cryovolcanism " is not possible. Furthermore, there is a lack of general agreement about the characteristics to be expected for the eruption and emplacement processes. Thus, one is forced to rely upon analysis supported by models and geological analogues on other solar system bodies. These analogue models are adjusted to a Titan setting. Required resurfacing rate: The required resur-facing rate turns out to be modest. Taking the age of Titan's surface as 500 My, consistent with the age ranges previously derived [7, 8], and its surface area of 8 x …