From Habitability to Life on Mars by Nathalie A. Cabrol Edmond A. Grin & Edmond A. Grin

Author:Nathalie A. Cabrol,Edmond A. Grin & Edmond A. Grin
Language: eng
Format: epub
ISBN: 9780128099360
Publisher: Elsevier Ltd.
Published: 2018-06-28T16:00:00+00:00

Fig. 7.4 Oblique CRISM colored HiRISE DEM project image of Nili Tholus volcanic cone. White-toned silica sinter deposits occur as mounds similar to those observed in large hydrothermal fields on Earth. Sinter deposits beneath the mound shown in the center of the image, located on the flank of Nili Tholus cone, radiates in a fan-shaped deposit oriented downslope, consistent with channelized outflow deposits from terrestrial hydrothermal effluents (Skok et al., 2010). Image Credit: NASA/JPL/MSSS/JHU-APL, CTX: P04_002427_1888_XI_08N292W, CRISM: FRT00010628.

As shown in Fig. 7.5, CRISM data also revealed that—when normalized to the surrounding materials—the proximal white-tone deposits have a strong, asymmetric 2.21-μm VNIR absorption feature, which is caused by a combination vibrational absorption (OH stretch and SiOH bend) (Skok et al., 2010). These deposits also have weak (even for Mars) hydration absorptions at 1.4 and 1.9 μm (cf., Skok et al., 2010; Sun et al., 2016a,b). In combination, these spectral absorptions are consistent with an opal-A sinter composition, an interpretation strengthened by the geological context and distribution of the deposits on, and adjacent to, the Nili Tholus volcanic cone within the Nili Patera caldera. Since the initial report of the discovery of these silica sinter deposits around Nili Tholus, additional Si-OH spectral signatures have been identified in several areas within the volcanic flows. Deposits with similar absorptions were also detected in regions to the west and southwest of the cone, all lying on an evolved silica-enriched unit identified by thermal infrared observations with the use of THEMIS (Christensen et al., 2005).

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