Comet Simulation experiments to measure thermo-mechanical properties of nuclei under solar illumination
Abstract
Although comet nuclei appear weak at large scales, the Philae lander first bounced off the surface of 67P, then the MUPUS penetrometer was unable to make its way inside the surface. Both observations suggest the presence of a layer of hard materials at depth. To better understand what this hard layer consists of and how it develops over time, we are developing a new simulation chamber to examine explore correlations between the composition of starting icy comet nucleus analog materials (dust-to-ice ratio, in particular), their thermal properties, their mechanical properties, and their evolution over depth and time. The primary approach is to synthesize porous cometary analogs with a wide range of dust-to-ice ratios, and simulate the variations in insolation they would be subject to along typical Jupiter-Family Comets orbits (scaled to timescales accessible in the laboratory) under high-vacuum conditions using a custom-built lamp with illumination modulation. In this context, "dust" refers to the refractory components of comet nuclei (e.g. silicates, large organic molecules), and "ice" to their volatile components (mostly H2O and CO2 ice in Jupiter-Family Comets). Temperature profiles are measured continuously using a custom-built thermal probe, and 2D time-dependent thermal modeling retrieves the thermal properties and their evolution as function of depth and time. A custom-built cone penetrometer apparatus measures the strength (resistance to penetration) of the comet analogs at various locations of the sample over the course of each experiment. We will report on the status of development of this new simulation chamber and preliminary results obtained to date.Acknowledgements: This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Copyright 2018, California Institute of Technology. Government sponsorship acknowledged.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E.647C