Abstract
From the operation of the MUPUS thermal probe Spohn et al. (2015) concluded that the material of the nucleus of 67P/Churyumov–Gerasimenko is likely to have a high strength, at least locally at the Philae landing site. In this work we consider the derived strength of the material in order to constrain its granulation. For this purpose we performed numerical simulations of the long-term sintering of ice–dust granular mixtures of different granulation, covered by a dust mantle. The dust mantle has a thickness of 0–16cm, and a (pore size and temperature-dependent) thermal conductivity. According to our simulations a hardened layer at least a meter thick forms beneath the dust only when the grains are tens of microns in radius, or smaller.
Highlights
After the final touch-down of the Rosetta lander Philae the MUPUS PEN probe was deployed in an attempt to measure, among other parameters, the local strength of the nucleus of Comet 67P/ Churyumov–Gerasimenko
The selected value of the Hertz factor is close to the efficiency limit of the considered sintering mechanism which is most effective under cometary conditions, i.e. the transport of molecules via the vapor phase from adjacent grains onto the connecting neck
We performed numerical simulations of the long-term sintering of ice–dust granular mixtures of different granulation in order to constrain the granulation of the Rosetta target Comet 67P/Chury umov–Gerasimenko
Summary
After the final touch-down of the Rosetta lander Philae the MUPUS PEN probe was deployed in an attempt to measure, among other parameters, the local strength of the nucleus of Comet 67P/ Churyumov–Gerasimenko. This probe, part of the MUPUS package (MUltiPUrpose Sensors for Surface and Sub-Surface Science) is equipped with 16 temperature sensors to be inserted into the soil by a hammer mechanism. The progress of the hammering was measured by a sensor. The depth sensor recorded an initial progress of about 20 mm and its readings oscillate for 3.5 h by a total of 5 mm, suggesting that no further penetration took place. The findings of the MUPUS experiment have been described in detail by Spohn et al (2015)
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