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. 2015 May 28;42(10):3746-3754.
doi: 10.1002/2015GL063824. Epub 2015 May 26.

Spectral properties of Titan's impact craters imply chemical weathering of its surface

C D Neish  1 , J W Barnes  2 , C Sotin  3 , S MacKenzie  2 , J M Soderblom  4 , S Le Mouélic  5 , R L Kirk  6 , B W Stiles  3 , M J Malaska  3 , A Le Gall  7 , R H Brown  8 , K H Baines  3 , B Buratti  3 , R N Clark  9 , P D Nicholson  10
Affiliations

Spectral properties of Titan's impact craters imply chemical weathering of its surface

C D Neish et al. Geophys Res Lett. .

Abstract

We examined the spectral properties of a selection of Titan's impact craters that represent a range of degradation states. The most degraded craters have rims and ejecta blankets with spectral characteristics that suggest that they are more enriched in water ice than the rims and ejecta blankets of the freshest craters on Titan. The progression is consistent with the chemical weathering of Titan's surface. We propose an evolutionary sequence such that Titan's craters expose an intimate mixture of water ice and organic materials, and chemical weathering by methane rainfall removes the soluble organic materials, leaving the insoluble organics and water ice behind. These observations support the idea that fluvial processes are active in Titan's equatorial regions.

Keywords: Titan; erosion and weathering; impact cratering.

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Figures

Figure 1
Figure 1
(a) Mosaic of Cassini VIMS observations of Titan in simple cylindrical projection. Colors are mapped with 4.8–5.2 µm as red, 2.00 µm as green, and 1.28 µm as blue. The locations of the three craters studied in this work are marked with white boxes. The 5 µm bright regions observed at high latitudes are clouds. (b) RADAR and (c) VIMS images of Sinlap crater, the least degraded crater in this study. (d) Synthetic aperture radar topography (SARTopo) profile through the northern edge of Sinlap crater, as reported in Neish et al. [2013a]. Profile line shown in red in Figure 1b. (e) RADAR and (f) VIMS images of the crater in Santorini Facula with (g) partial digital terrain model. Dunes are seen on the crater floor in Figure 1e. (h) RADAR and (i) VIMS images of Soi crater, the flattest known crater on Titan. (j) A digital terrain model of Soi indicates a depth of only 240 ± 120 m.
Figure 2
Figure 2
(a) Cassini RADAR image of Sinlap crater. (b) New Cassini VIMS image of Sinlap crater, acquired with a pixel scale that ranges between ~1 and 4 km (CM_1790056808_1), placed over a lower resolution image of the same region (CM_1525118253_1). The color scheme is the same as that in Figure 1. (c) RADAR image colorized with VIMS data. (d) Annotated version of the colorized RADAR image. Features discussed in the text are indicated with white arrows.
Figure 3
Figure 3
(a–c) A proposed progression of impact crater degradation on Titan, as seen in (left) side view and (right) plan view. Blue materials are inferred to be water ice rich, brown materials are correlated with regions of sand dunes, and yellowish‐green materials represent an as‐yet unknown material, presumably more enriched in organic material.
See this image and copyright information in PMC

References

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