Thermal Inertia Mapping Using Mars Climate Sounder Measurements.

Abstract:

Previous work has shown inter-seasonal variations of the apparent thermal inertia at virtually all Martian latitudes. Because thermal inertia is mainly controlled by low variability parameters (e.g., grain sizes, degree of induration, rock abundance), these variations are usually interpreted in terms of subsurface layering and atmospheric contributions.

Using atmospherically corrected surface temperatures at 32 μm wavelength (channel B1) from the Mars Climate Sounder (MCS) onboard Mars Reconnaissance Orbiter, we analyze the inter-seasonal variations of the apparent thermal inertia. We show that most of the previously observed inertia variations are eliminated, indicating that a simple homogeneous regolith structure is sufficient to explain most of the measurements. Also, as expected, a fraction of the observed variations remain, especially at high latitudes. This is consistent with subsurface layering involving water ice below dry regolith inferred from other measurement techniques and modeling.

This work strengthens our ability to identify and characterize surface/subsurface material thermal inertias, layering and physical heterogeneities in the Martian surface layer, and will help eliminate seasonal striping on high-resolution inertia maps. In addition to a global scale analysis, we will discuss observations in western Elysium Planitia where the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander is planned to land in September 2016. We will provide predictions of the surface layer thermophysical properties, which are required for safe landing and successful scientific operations on the ground.