Thermal expansion and phase changes in methane and nitrogen at Pluto temperatures
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Date
2018-03-22
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Universities Space Research Association
Abstract
Introduction:
Some of the most striking images from the New Horizons fly-by of Pluto were of the towering mountains surrounded by seemingly flowing glacial terrain (Figure 1) [1]. The explanation for this terrain has its basis in
crystallography, where at 44 K the strength of the hydrogen bond endows water ice with the resilience to build such mountains, while the rotational disorder in the solid structure of methane [2] and nitrogen [3] allow these
materials to flow plastically even at 44K. These interpretations have been strengthened by the spectral observations that correlate these materials to the respective terrains [4]. In order to undertake accurate modelling of the geological features on Pluto the physical properties of the constituent materials must be well constrained. There is much still to be understood about the interactions and structural behaviours at these frigid temperatures, and crystallographic investigations can play a vital role in characterising these. Although water-ice has been the subject of intensive laboratory studies, the same cannot be said of methane and nitrogen. The thermal expansions of these materials have been investigated [5], but only to a lowest temperature of 40 K and using techniques which were largely insensitive to, in particular, the hydrogen positions within methane. Thus, the aim of the experiments reported here is to investigate the structures of the phases formed and determine the thermal expansion of methane and nitrogen over temperatures relevant to Plutonian processes using neutron diffraction.
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Keywords
Neutron diffraction, Crystallography, Nitrogen, Methane, Phase transformations, Pluto planet, Space vehicles
Citation
Brand, H. E. A. & Maynard-Casely, H. E. (2018). Thermal expansion and phase changes in methane and nitrogen at Pluto temperatures. Poster presented at the 49th Lunar and Planetary Science Conference, The Woodlands, Texas, USA, March 19-23, 2018 (No. 2083, pp. 1839). Retrieved from: https://www.hou.usra.edu/meetings/lpsc2018/program/