Mathematics – Logic
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p22a..03k&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P22A-03
Mathematics
Logic
[1221] Geodesy And Gravity / Lunar And Planetary Geodesy And Gravity, [5464] Planetary Sciences: Solid Surface Planets / Remote Sensing, [5480] Planetary Sciences: Solid Surface Planets / Volcanism, [6281] Planetary Sciences: Solar System Objects / Titan
Scientific paper
Determining whether cryovolcanism has occurred on Titan is of pressing interest because eruptions have been suggested to resupply atmospheric methane, replacing what is lost by photolysis. Cryovolcanism also has intrinsic interest as a posited but largely undocumented geologic process on Titan. Most candidate cryovolcanoes on Titan have been proposed based on photointerpretation (i.e., analogy between their morphology and that of volcanic features on the Earth and other silicate bodies) based on RADAR SAR images with 300-1500 m resolution (e.g., Rohe Fluctus, Ganesa Macula, Hotei Regio) or VIMS infrared images with multi-km resolution (Tortola Facula, Tui Regio). RADAR provides a higher resolution check of the VIMS candidates, weakening the case for Tortola and supporting that for Tui, but definitive determination may require even higher resolution imaging by a future mission. Fortunately, topography provides important additional clues. Digital topographic models (DTMs) produced by stereoanalysis of RADAR images are particularly valuable because they permit features to be visualized in 3D; other methods provide only isolated topographic profiles. RADAR stereo covers only a few percent of Titan but has provided compelling evidence for or against several candidate cryovolcanoes. Ganesa Macula was a leading early candidate because of its resemblance to steep-sided volcanic domes on Venus, but stereo mapping showed that the feature is irregular in relief, with a generally elevated eastern and low western margin. It is clearly not a dome; it may have started as one but has been drastically modified. Lobate radar-bright and -dark features in Hotei Regio were suggested as volcanic flows, but have also been interpreted as fluvial. Our DTM shows the flows to be 100-200 m thick, with bright tops and dark margins. Towering over nearby fluvial channels, they seem unlikely to be sedimentary deposits of fluvial origin. Thus, by elimination, the cryovolcanic hypothesis is strengthened. We recently mapped Sotra Facula (a 60 km subcircular feature near 40°W 15°S from which lobate flows radiate northward 180 km) and found even clearer evidence for volcanism. Unlike most dune-free areas in the equatorial sand seas (including Tortola), which are nondescript rises with only a few hundred m of relief, Sotra includes a 1000-m high peak and an adjacent 1500-m deep pit from which the flows appear to originate. The apparent thickness of the flows ranges from zero where they are locally crossed by dunes to 800 m, suggesting that they have been extensively modified. No fluvial features are found in the vicinity, but 450 km north of Sotra is a second 1000-m peak surrounded by smaller flow lobes that resemble an area of western Xanadu previously suggested to be volcanic. The Sotra area thus seems to be a leading candidate for a cryovolcanic field on Titan.
Barnes Jason W.
Hayes Alexander G.
Howington-Kraus Elpitha
Kirk Randolph L.
Lopes Rosaly M.
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