Estimation of surface temperatures on Mercury in preparation of the MERTIS experiment onboard BepiColombo

Abstract

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is part of the payload on the joint ESA-JAXA BepiColombo Mission, launched in October 2018. The spectrometer is designed to map surface composition, identify rock-forming minerals, map surface mineralogy, and study surface temperature variations. The surface of Mercury undergoes large temperature variations depending on solar irradiation. Mineral spectra show significant changes in spectral features with changing temperature. In preparation of the experiment, we developed a thermal model that calculates surface temperatures based on appropriate insolation conditions and thermo-physical properties. This model has been validated with lunar parameters and hence been applied to the conditions of Mercury. Here we present surface temperature maps based on MESSENGER albedo and topography data. The results have been compared to previous models and measurements of Mercury's surface temperatures.The surface of Mercury undergoes large temperature variations each diurnal period. At the equator temperatures vary between less than 100 K during the night up to 700 K at local noon at longitudes 0° W and 180° W, and up to 570 K at longitudes 90° W and 270° W. Due to the 3:2 spin orbit resonance local noon at longitudes 0° W and 180° W coincide with perihelion, while longitudes 90° W and 270° W experience local noon at aphelion, which results in “hot” and “warm” poles around the equator. At 45° N surface temperatures at local noon reach 645 K (0° W and 180° W) and 510 K (90° W and 270° W).