Inferring the composition of the liquid surface on Titan at the Huygens probe landing site from Surface Science Package measurements

Abstract

With Huygens’ descent into Titan’s atmosphere drawing nearer, the composition and state of Titan’s surface remained largely unknown. The idea of a global ocean on Titan has become less popular over the last decade, though the possibility of lakes and seas has remained, and recently [Campbell, D.B., Black, G.J., Carter, L.M., Ostro, S.J. Radar evidence for liquid surfaces on Titan. Science 302, 431–434, 2003] reported radar evidence for liquid surfaces. Ground truth for the existence of an ocean, sea or lake on Titan or, more precisely, a liquid surface at the specific impact point of the Huygens probe, came from the sensors of the Huygens Surface Science Package (SSP). The state of the surface material can be derived on impact using the onboard accelerometers. In the case of an impact into a liquid the SSP sensors would have been able to measure not only density but also acoustic properties, permittivity, refractive index and thermal properties. In this work, we describe possible ways of constraining the composition of a liquid surface on Titan by combining various measurements made by SSP.