While landing on Titan, several instruments onboard Huygens acquiredmeasurements that indicate the probe did not immediately come to rest. Detailedknowledge of the probe's motion can provide insight into the nature of Titan'ssurface. Combining accelerometer data from the Huygens Atmospheric StructureInstrument (HASI) and the Surface Science Package (SSP) with photometry datafrom the Descent Imager/Spectral Radiometer (DISR) we develop a quantitativemodel to describe motion of the probe, and its interaction with the surface.The most likely scenario is the following. Upon impact, Huygens created a 12 cmdeep hole in the surface of Titan. It bounced back, out of the hole onto theflat surface, after which it commenced a 30-40 cm long slide in the southwarddirection. The slide ended with the probe out of balance, tilted in thedirection of DISR by around 10 degrees. The probe then wobbled back and forthfive times in the north-south direction, during which it probably encountered a1-2 cm sized pebble. The SSP provides evidence for movement up to 10 s afterimpact. This scenario puts the following constraints on the physical propertiesof the surface. For the slide over the surface we determine a frictioncoefficient of 0.4. While this value is not necessarily representative for thesurface itself due to the presence of protruding structures on the bottom ofthe probe, the dynamics appear to be consistent with a surface consistency ofdamp sand. Additionally, we find that spectral changes observed in the firstfour seconds after landing are consistent with a transient dust cloud, createdby the impact of the turbulent wake behind the probe on the surface. Theoptical properties of the dust particles are consistent with those of Titanaerosols from Tomasko et al. (P&SS 56, 669). We suggest that the surface at thelanding site was covered by a dust layer, possibly the 7 mm layer of...
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