Iapetus surface variability revealed from statistical clustering of a VIMS mosaic: The distribution of CO2

• Published in: Icarus (New York, N.Y. 1962) Vol. 215; no. 1; pp. 75 - 82
• Main Authors: PINILLA-ALONSO, Noemi, ROUSH, Ted L, MARZO, Giuseppe A, CRUIKSHANK, Dale P, DALLE ORE, Cristina M
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.09.2011
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Solar system; Phoebe; Spectroscopy; Satellites, Composition; Iapetus; Absorption band; Variability; Satellites, Surfaces; Saturn satellite; Ice; Ices; Solar system
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2011.07.004

We present a detailed study of an Iapetus mosaic of VIMS data with high spatial resolution (0.50.5 degree or a arrow right 46.4km/pixel). The spectra were taken in August 2007 and provide the highest VIMS spatial resolution data for this object during Cassini's primary mission. We analyze this set of data using a statistical clustering approach to reduce the analysis of a large number of data (a arrow right 4104 spectra from 0.35 to 5.10 mu m) to the study of seven representative groups accounting for 99.6% of the surface covered by the original sample. We analyze the spectral absorption bands in the spectra of the different clusters indicative of different composition over the observed surface. We find coherence between the distribution of the clusters and the geographical features on the surface. We give special attention to the study of the water ice and CO2 bands. We find that CO2 is widespread over the entire surface being studied, including the bright and dark areas on Iapetus' surface, and is probably trapped at the molecular level with other materials. The strength of the CO2 band in the areas where both, H2O- and carbon-bearing materials exist, gives support to the hypothesis that this volatile is formed on the surface of Iapetus as a product of irradiation of these two components. Finally, we also compare the Iapetus CO2 with that on other satellites confirming, that there are evident differences on the center, depth and width of the band on Iapetus and Phoebe, where CO2 has been suggested to be endogenous.