TY - JOUR A1 - Bürger, Johanna A1 - Hayne, Paul A1 - Gundlach, Bastian A1 - Läuter, Matthias A1 - Kramer, Tobias A1 - Blum, Jürgen T1 - A Microphysical Thermal Model for the Lunar Regolith: Investigating the Latitudinal Dependence of Regolith Properties JF - Journal of Geophysical Research: Planets N2 - The microphysical structure of the lunar regolith provides information on the geologic history of the Moon. We used remote sensing measurements of thermal emission and a thermophysical model to determine the microphysical properties of the lunar regolith. We expand upon previous investigations by developing a microphysical thermal model, which more directly simulates regolith properties, such as grain size and volume filling factor. The modeled temperatures are matched with surface temperatures measured by the Diviner Lunar Radiometer Experiment on board the Lunar Reconnaissance Orbiter. The maria and highlands are investigated separately and characterized in the model by a difference in albedo and grain density. We find similar regolith temperatures for both terrains, which can be well described by similar volume filling factor profiles and mean grain sizes obtained from returned Apollo samples. We also investigate a significantly lower thermal conductivity for highlands, which formally also gives a very good solution, but in a parameter range that is well outside the Apollo data. We then study the latitudinal dependence of regolith properties up to ±80° latitude. When assuming constant regolith properties, we find that a variation of the solar incidence-dependent albedo can reduce the initially observed latitudinal gradient between model and Diviner measurements significantly. A better match between measurements and model can be achieved by a variation in intrinsic regolith properties with a decrease in bulk density with increasing latitude. We find that a variation in grain size alone cannot explain the Diviner measurements at higher latitudes. Y1 - 2024 U6 - https://doi.org/10.1029/2023JE008152 VL - 129 IS - 3 ER - TY - CHAP A1 - Bürger, Johanna A1 - Hayne, Paul A1 - Gundlach, Bastian A1 - Läuter, Matthias A1 - Kramer, Tobias A1 - Blum, Jürgen T1 - Investigating the Latitudinal Dependence of Lunar Regolith Properties Using LRO/Diviner Data and a Microphysical Thermal Model T2 - Bulletin of the AAS N2 - Regolith is formed through weathering of the local rock by meteorite bombardment, space weathering (Pieters & Noble, 2016) and thermal erosion (Delbo et al., 2014). In the case of the Moon, the space weathering effects and diurnal temperature variations are reduced towards the poles. The aim of this study is to investigate whether the lunar regolith properties derived from the comparison of regolith temperatures measured by the Diviner radiometer (Paige et al., 2010) on board the Lunar Reconnaissance Orbiter (LRO) with simulated temperatures derived from a microphysical thermal model show a latitudinal dependence. The developed microphysical thermal model expands upon previous models by more directly simulating regolith properties, such as grain radius and volume filling factor. Y1 - 2023 UR - https://baas.aas.org/pub/2023n8i207p02 VL - 55 IS - 8 ER - TY - CHAP A1 - Läuter, Matthias A1 - Kramer, Tobias T1 - Non-gravitational acceleration and torque on comet 67P/Churyumov-Gerasimenko T2 - Bulletin of the AAS N2 - From August 2014 to September 2016, the ESA operated the Rosetta spacecraft mission alongside with comet 67P/Churyumov-Gerasimenko (67P). The mission provided valuable long-term data on the comet’s nucleus, including its volume, mass, tensor of inertia, spatial position of the orbital trajectory, and rotational state. Y1 - 2023 UR - https://baas.aas.org/pub/2023n8i218p02 VL - 55 IS - 8 ER - TY - JOUR A1 - Läuter, Matthias A1 - Kramer, Tobias A1 - Rubin, Martin A1 - Altwegg, Kathrin T1 - The ice composition close to the surface of comet 67P/Churyumov-Gerasimenko JF - ACS Earth and Space Chemistry N2 - The relation between ice composition in the nucleus of comet 67P/Churyumov-Gerasimenko on the one hand and relative abundances of volatiles in the coma on the other hand is important for the interpretation of density measurements in the environment of the cometary nucleus. For the 2015 apparition, in situ measurements from the two ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) sensors COPS (COmet Pressure Sensor) and DFMS (Double Focusing Mass Spectrometer) determined gas densities at the spacecraft position for the 14 gas species H2O, CO2, CO, H2S, O2, C2H6, CH3OH, H2CO, CH4, NH3, HCN, C2H5OH, OCS, and CS2. We derive the spatial distribution of the gas emissions on the complex shape of the nucleus separately for 50 subintervals of the two-year mission time. The most active patches of gas emission are identified on the surface. We retrieve the relation between solar irradiation and observed emissions from these patches. The emission rates are compared to a minimal thermophysical model to infer the surface active fraction of H2O and CO2. We obtain characteristic differences in the ice composition close to the surface between the two hemispheres with a reduced abundance of CO2 ice on the northern hemisphere (locations with positive latitude). We do not see significant differences for the ice composition on the two lobes of 67P/C-G. Y1 - 2022 U6 - https://doi.org/10.1021/acsearthspacechem.1c00378 VL - 6 IS - 5 SP - 1189 EP - 1203 ER - TY - CHAP A1 - Kramer, Tobias A1 - Läuter, Matthias T1 - Matching the activity of comet 67P/Churyumov-Gerasimenko with long-term ground-based astrometry T2 - Europlanet Science Congress N2 - 50 years of astrometric data for comet 67P/C-G (orbital period about 6.45 years) provides a unique opportunity to benchmark non-gravitational acceleration models to the in situ measurements of the volatile release performed from the Rosetta rendezvous mission (2014-2016). Taken together, the Earth-bound and in-situ data yields lower fit errors and serves as a test-case for our ability to deduce thermophysical quantities of cometary nuclei from the Earth-bound observations. Y1 - 2021 U6 - https://doi.org/10.5194/epsc2021-337 VL - 15 SP - EPSC2021-337 PB - Europlanet Science Congress ER - TY - CHAP A1 - Läuter, Matthias A1 - Kramer, Tobias A1 - Rubin, Martin A1 - Altwegg, Kathrin T1 - Gas production of comet 67P/Churyumov-Gerasimenko reconstructed from DFMS/COPS data T2 - Europlanet Science Congress N2 - We reconstruct the temporal evolution of surface emissions for the four major gas species H2O, CO2, CO, and O2 emitted during the 2015 apparition of comet 67P/Churyumov-Gerasimenko (67P/C-G). Measurements from the Double Focusing Mass Spectrometer (DFMS) of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the COmet Pressure Sensor (COPS) are used to determine the gas sources on the surface with an inverse gas model for the entire coma. For all species, peak production rates and integrated production rates per orbit are evaluated separately for the northern and the southern hemisphere. Complemented with the total mass production, this allows us to estimate the dust-to-gas ratio of the emitted material. Y1 - 2018 VL - 12 SP - EPSC2018-515-1 PB - Europlanet Science Congress ER - TY - CHAP A1 - Kramer, Tobias A1 - Läuter, Matthias T1 - Modelling the inner coma of comet 67P/Churyumov-Gerasimenko T2 - Europlanet Science Congress N2 - Based on about 1 million of pressure measurements around comet 67P/Churyumov-Gerasimenko we reconstruct the gas emission across the entire nucleus. Dust particles are seeded in the gas model and the resulting dust distribution follows a daily pattern which agrees with observations if a uniform dust release across the entire sunlit surface is assumed. Y1 - 2018 VL - 12 SP - EPSC2018-115-1 PB - Europlanet Science Congress ER -