Compositional Mapping of Europa Using MCMC Modelling of Near-IR VLT/SPHERE and Galileo/NIMS Observations

By Keith Cowing
March 7, 2022
Filed under
Compositional Mapping of Europa Using MCMC Modelling of Near-IR VLT/SPHERE and Galileo/NIMS Observations
Map of spatial coverage of the datasets used in this study. The black dotted line shows the useful spatial coverage of the VLT/SPHERE observation. The coloured outlines show the total area observed in each NIMS dataset (see Table 2). The shaded orange region shows the area of the ‘E6’ observation where NIMS has full spectral coverage of the SPHERE wavelength range, which is used for full spectral modelling. Regions with extreme emission and incidence angles (> 75°) have large residual photometric errors, so are not used in this study or shown on this map. The background visible light reference image of Europa is from Becker (2013). 0°W is the sub-jovian longitude and 180°W is the anti-jovian longitude.

We present maps of surface composition of Europa’s anti-jovian hemisphere acquired using high spatial resolution IFU multi-spectral data from the SPHERE instrument on the Very Large Telescope (0.95 to 1.65μm) and the NIMS instrument on the Galileo orbiter (0.7 to 5.2μm).

Spectral modelling was performed using a Markov Chain Monte Carlo method to estimate endmember abundances and to quantify their associated uncertainties. Modelling results support the leading-trailing hemisphere difference in hydrated sulphuric acid abundances caused by exogenic plasma bombardment. Water ice grains are found to be in the 100μm to 1mm range, with larger grains present on the trailing hemisphere, consistent with radiation driven sputtering destroying smaller grains.

Modelling best estimates suggest a mixture of sulphate and chlorinated salts, although uncertainties derived from the MCMC modelling suggest that it is difficult to confidently detect individual salt abundances with low spectral resolution spectra from SPHERE and NIMS. The high spatial resolution offered by SPHERE allows the small scale spatial distribution (<150km) of potential species to be mapped, including ground-based detection of lineae and impact features. This could be used in combination with other higher spectral resolution observations to confirm the presence of these species. Oliver King, Leigh N Fletcher, Nicolas Ligier Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2203.02367 [astro-ph.EP] (or arXiv:2203.02367v1 [astro-ph.EP] for this version)
Submission history
From: Oliver King
[v1] Fri, 4 Mar 2022 15:07:20 UTC (23,220 KB)

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