Investigating the Physical Properties of Planetary Surfaces using the Huygens Penetrometer

Abstract

The Huygens probe landed on the unknown surface of Titan on 14 January 2005. Onboard, a small, protruding hemispherical-tipped penetrometer, ACC-E, part of the Surface Science Packagem impacted the surface returning a short ~20 ms force signature of the mechanical resistance of the ground. The purpose of this thesis is to examine the response of an identical penetrometer to various terrestrial target materials and provide an insight into the penetrometer's performance and assess its capability. Signatures collected at the Huygens impact speed of both natural and artificial material targets in the laboratory are examined using various descriptive statistical measures. Structural and textural properties are identified and the penetrometer's response to granular targets, both wet and dry, is examined. Mitigation of the effects of target boundaries and velocity dependence of the signatures are both considered. Terrestrial fieldwork penetrometry is presented that demonstrates that even for short penetration depths the sensor is capable of distinguishing several types of geological surface features. A physical model extended for layered targets is presented and applied to laboratory data. Using the results from the laboratory and fieldwork, together with more specific experiments, a possible interpretation of the signature returned from Titan is presented and discussed within the context of recent findings from other investigations