Mercury: Current and Future Science 2018 (LPI Contrib. No. 2047) 6040.pdf

THE SHAKESPEARE (H-03) QUADRANGLE OF MERCURY: FROM COLOR MAPPING TO DISTINC- TION OF LITHOLOGICAL HETEROGENEITIES. N. Bott1, A. Doressoundiram1, D. Perna1,2, F. Zambon3, C. Carli3, F. Capaccioni3, 1LESIA - Observatoire de Paris - CNRS - Sorbonne Université - Université Paris-Diderot (5 place Jules Janssen, 92195 Meudon, France; [email protected]), 2Osservatorio Astronomico di Roma - INAF, Monte Porzio Catone, Italy, 3Istituto di Astrofisica e Planetologia Spaziali - INAF, Roma, Italy.

Introduction: Mercury mapping campaign started to support the observational strategy of the SIMBIO- SYS instrument onboard the future BepiColombo spacecraft. A goal is to integrate the color variations due to differences in composition to the photo-inter- preted geology of the innermost planet. The used data are image mosaics from the Mercury Dual Imaging System (MDIS) Wide Angle Camera (WAC) onboard MESSENGER spacecraft. Authors identified three ma- jor color units (high-reflectance plains, intermediate terrains and low-reflectance material) and two minor color units (red spots and hollows) [1]. We analysed the spectral properties of the surface in the H-03 quad- Fig. 1. Example of spectral parameter map of the Shake- rangle to define its compositional variability and iden- speare quadrangle using a thresholding of PC2 values. tify units constrained by opportune spectral parameters. Data Set: The surface of Mercury is subdivided For example, it appears on the above map that the into 15 quadrangles. Some have already been mapped floor of Degas crater (cyan) is clearly distinct from [2,3], others are in progress [4]. Here we focus on the other terrains (Sobkou planitia, in yellow on the left) in H-03 quadrangle, Shakespeare, with 22.5° < latitude < term of values of PC2. As PC2 highlights the spectral 65° and 180° < longitude < 270°. We used the data of slope variations, it means that the floor of this young the 8 following filters: 433.2, 479.9, 558.9, 628.8, crater has a spectral slope distinct from the rest of the 748.7, 828.4, 898.8 and 996.2 nm. The other filters quadrangle. This is confirmed on the plot of the nor- (698.8, 947.0 and 1012.6 nm) can not ensure the cover- malized averaged spectra of each unit defined by the age of the quadrangle. threshold of this parameter (embedded graph, Fig. 1). Method: To produce the color map, we used the More analyses of spectral parameters will be presented. software ISIS (USGS) and we proceeded as follows: 1) Future Works: This work on spectral properties of Importation of raw data into ISIS format; 2) Georefer- the surface material present in the Shakespeare quad- encing using SPICE kernels and a DEM produced at rangle will be integrated to the geological map of the DLR [5]; 3) Radiometric calibration; 4) Equirectangu- Shakespeare quadrangle produced by [9], and aims to lar projection; 5) Kaasalainen-Shkuratov photometric define higher level units to produce a more accurate correction [6, Table 9] to report the data at standard il- map of this quadrangle. lumination conditions (inc. i=30°, em. e=0°); 6) Coreg- Acknowledgements: This work is partly supported istration of images to obtain the mosaic of Shakespeare by the Centre National d’Etudes Spatiales. D. Perna re- Results: Color mapping. We applied techniques of ceived funding from the European Union’s Horizon image analysis, such as RGB color combinations and 2020 research and innovation programm under the Principal Component Analysis [7], to emphasize differ- Marie Sklodowska-Curie grant agreement n.664931. ences in spectral properties which can be correlated to References: [1] Blewett et al. (2009) E&PSL., 285, variations in composition. Examples of RGB maps of 272-282. [2] Galluzzi et al. (2016) Journ. of Maps, 12, Shakespeare have been shown recently [8]. We will ex- 227-238. [3] Zambon et al. (2016) Geophys. Research pose and discuss the last updates. Abstracts, 18, EGU2016-16909. [4] Giacomini et al. Spectral mapping. From the mosaic 8-color map- (2017) Geophys. Research Abs., 19, EGU2017-14574. ping, it is possible to infer interesting spectral parame- [5] Preusker et al. (2017) LPS XLVIII, abstract #1441 ters to identify units associated to specific terrains. [6] Domingue et al. (2016) Icarus, 268, 172-203. [7] Considering a thresholding of the values of a spectral Denevi et al. (2009) Science, 324, 613-618. [8] Bott et parameters (reflectance at 750 nm, PC2...), we ob- al. (2017) EPSC abstracts, 11, EPSC2017-283. [9] tained indications of units, showing different terrains Guzzetta et al. (2017) Journ. of Maps, 13, 227-238. with probable differences in composition (Figure 1).