Thermal and Mechanical Properties of the Near-Surface Layers of comet 67P/Churyumov-Gerasimenko

Spohn T., Knollenberg J., Ball A.J., Banaszkiewicz M., Benkhoff J., Grott M., Grygorczuk J., Hüttig C., Hagermann A., Kargl G., Kaufmann E., Kömle N., Kührt E., Kossacki K.J., Marczewski W., Pelivan I., Schrödter R., Seiferlin K.


349 (6247), 2015, art. aab0464, 10.1126/science.aab0464

Thermal and mechanical material properties determine comet evolution and even solar system formation because comets are considered remnant volatile-rich planetesimals. Using data from the Multipurpose Sensors for Surface and Sub-Surface Science (MUPUS) instrument package gathered at the Philae landing site Abydos on comet 67P/Churyumov-Gerasimenko, we found the diurnal temperature to vary between 90 and 130 K. The surface emissivity was 0.97, and the local thermal inertia was 85 ± 35 J m−2 K−1s-1/2. The MUPUS thermal probe did not fully penetrate the near-surface layers, suggesting a local resistance of the ground to penetration of >4 megapascals, equivalent to >2 megapascal uniaxial compressive strength. A sintered near-surface microporous dust-ice layer with a porosity of 30 to 65% is consistent with the data.