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Evolution study of ices-rich areas on comet 67P/CG using the QuACK map projection

Presentation #322.17 in the session Comets (Poster + Lightning Talk)

Published onOct 23, 2023
Evolution study of ices-rich areas on comet 67P/CG using the QuACK map projection

Water and carbon dioxide are the only two ice species recognized on the surface of comet 67P/Churyumov-Gerasimenko by means of their respective IR spectral absorption features by VIRTIS [1] onboard Rosetta. The crystalline water ice manifested its presence in different modalities: 1) on the active areas of the Hapi region where water ice frost cyclically changes its abundance with local time and illumination conditions, as a result of condensation during the night followed by sublimation after dawn [2]; 2) on recent debris fields at the base of collapsed structures located in the Imhotep region where pristine material has been recently exposed [3] and in numerous bright spots across the nucleus where single or multiple icy patches have been recognized [4, 5]; 3) in the internal structure of boulders exposed after the impact of the Philae lander [6]. CO2 ice has been detected by VIRTIS across a 60x80 m wide area placed in the Anhur region while progressing towards the dayside after a four years-long night season [7]. The study of the temporal evolution of these deposits on remotely sensed data is complicated by the rough morphology of the nucleus and by the degeneration of the coordinates in standard mapping projections [8, 9]. To overcome these limitations, the Quincuncial Adaptive Closed Kohonen (QuACK) mapping tool has been developed [10] with the aim to map and display all points of the nucleus surface in a generalized representation. After the successful application of the QuACK method to OSIRIS camera images [11], here we show the first results of the method applied to VIRTIS hyperspectral data with the aim of better demarcating the ices distribution and their temporal evolution across the 67P nucleus surface.

References: [1] Coradini, A. et al., SSR, 128 (2007). [2] De Sanctis, M.C. et al., Nature, 525 (2015). [3] Filacchione, G. et al., Nature, 529 (2016). [4] Barucci, M.A. et al., A&A, 595 (2016). [5] S. Fornasier, S. et al., A&A, 672, A136 (2023). [6] O’Rourke, L., et al, Nature, 586 (2020). [7] Filacchione, G. et al., Science, 354, 1563-1566 (2016). [8] Raponi, A. et al., MNRAS, 462 (2016). [9] Ciarniello, M. et al., MNRAS, 462 (2016). [10] Grieger, B. A&A 630, A1, 2019. [11] Leon-Dasi, M. A&A 652, A52 (2021).

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