Seasonal thermal inertia variations at Gale crater: Role of active surface deposition phenomena

Abstract

Thermal inertia has been found to play a significant role in planetary remote sensing applications, forming the basis of potentially all major lithological discriminations of the planetary surface. It has always been visualised to serve as a distinctive thermal property of the surface with its values remaining fairly constant at least for a short time period, unless the surface undergoes extensive and rapid degradation. Thermal inertia for Mars has been previously calculated from point spectrometer, orbiter and rover measurements and they have been successfully used for surface geologic interpretations. The present study computes surface thermal inertia over 12 sols along Curiosity's traverse at Gale crater using Thermal Infrared Imaging System (THEMIS) and Rover Environmental Monitoring Station (REMS) observations and attempts to analyse the same on a seasonal timescale. We find that surface thermal inertia at Gale follows a seasonal sinusoidal behaviour with the surface exhibiting maximum and minimum thermal inertia values during southern autumn and spring respectively, the difference between them of the order of 300 to 400 t.i.u. We have attempted here to illustrate that the seasonal behaviour seen in surface thermal inertia may be the result of active surface deposition processes localised to Gale. In this regard, we have also explored the potential role of seasonal dust and water ice deposition in contributing to these observed variations, effectively concluding that seasonal dust deposition could be a highly likely cause to which these seasonal thermal inertia changes can be attributed to.