Thermal Inertia of MASCOT landing site revisited with Digital Terrain Model
Abstract
JAXA's Hayabusa2 spacecraft delivered the European MASCOT lander to the surface of asteroid (162173) Ryugu [1,2]. A radiometer (MARA) was part of the MASCOT payloadand measured the surface brightness temperature of a single boulder for an entire asteroid rotation [3]. We incorporate a recently published 3D shape model of the boulder [4] into the DTM of the landing site, thus defining the surface orientation that was a free parameter in the initial analysis [3,5]. Using a thermophysical model we calculate the diurnal temperature variation for the multi-scale DTM and fit thermal inertia and emissivity of the boulder to the MARA observations. The recently published thermal inertia map of Ryugu [6] is used to calculate the temperatures of the landing site region around the observed boulder. We find that the rough shape of the boulder causes a systematic reduction of the daytime temperatures, as observed by MARA. The shape model is too coarse to fully reproduce the roughness effect and further roughness corrections need to be applied. Furthermore, in order to explain the strong increase in temperature in the early local morning, a specular reflection of sunlight from MASCOT into the instrument field of view has to be included. The updated thermal inertia estimate is lower than the previous upper limit estimate of 325 J m-2 K-1 s-1/2. The emissivity estimate of 0.9 - 1 is confirmed.
References: [1] Ho, T.M., et al., (2017) SSR 208, 339 [2] Jaumann, R., et al. (2019) Science, 365, 6455, 817-820 [3]Grott, M., et al., (2019) Nature, 3, 971-976 [4] Scholten, F., et al., (2019) A&A, 632, L5 [5] Hamm, M., et al., (2020) MNRAS, 496, 3, 2776-2785 [6] Shimaki, Y., et al. (2020) Icarus, 348, 113835- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMP037...08H
- Keywords:
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- 6017 Erosion and weathering;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6024 Interiors;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6025 Interactions with solar wind plasma and fields;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6055 Surfaces;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES