22-EPN3-019: Investigation of Ceres Bright Spots
January 23, 2024

22-EPN3-019: Investigation of Ceres Bright Spots – VIS-NIR Spectral Simulation of Haulani bright Areas by Means of Spectral Analysis on Produced Analogue Mixtures

Visit by Fabrizio Dirri and Giuseppe Massa (INAF-IAPS, Italy) to TA2.8 CSS (Cold Surfaces Spectroscopy) at IPAG (France).
Dates of visit: 22 May – 03 June 2023

Report Summary: In this project different bright areas of Haulani crater (i.e. Southern floor and Central Crater Peak, named ROI3 and ROI1) on Ceres have been studied by producing different analogue mixtures starting from previous results and comparing them with Dawn VIR data. The end-members have been identified based on previous studies (Tosi et al. 2018, Dirri et al. 2022) and the analogue mixtures have been produced with grain size 50-100 µm. The two initial mixtures, i.e. SF1 and CCP_#1 have been acquired in the VIS-NIR spectral range (0.4-4.5 µm) at T environment. The Band Center, Band Depth and FWHM of absorption bands at 2.7, 3.1, 3.4 µm, spectral slope (1.2-1.9 µm range) and reflectance level at 2.1 µm of the produced SFs and CCPs mixtures have been analysed and then compared with VIR data.

The best analogues are the SF_#5 and CCP_#6 mixtures and their spectra have been acquired at low temperatures, i.e. from 190K to 230K, similar to Haulani base temperature by using Cold Spectroscopy Facility (CSS) (IPAG, France). These mixtures exhibit values for the 2.7BD (Antigorite, Illite), 3.1BD (NH4-Montmorillonite) and 3.4 BD (NaCO3) similar to Haulani ROI3 and ROI1. In particular, different dark components have been used (i.e. magnetite plus carbon black) with the aims of better reproducing the Haulani spectral slope and reflectance level. Different carbonates mix involving trona, dolomite, hydrous and anhydrous natrite have been studied to assess their contribution to 2.7 µm spectral band and the three minima at 3.33, 3.42, 3.52 µm of Haulani ROI3.