Final Cassini RADAR Observation of Titan's Magic Island Region and Ligeia Mare
Abstract
Cassini arrived in the Saturn system shortly after the Oct. 2002 northern winter solstice and the mission will end shortly after the May 2017 northern summer solstice. A main objective of the Cassini Solstice mission is to study seasonal and temporal changes and at Titan this includes changes of the hydrocarbon lakes/seas. Titan's Magic Islands are transient bright features in the north polar sea, Ligeia Mare that were observed to be temporal changes in Cassini RADAR images. The Magic Islands were discovered in a July 2013 image as anomalously bright features that were not present in four previous observations from Feb. 2007 - May 2013. The region of the Magic Islands was again anomalously bright in an Aug. 2014 image and the total areal extent of the anomalously bright region had increased by more than a factor of three. The transient features were not, however, observed in a Jan. 2015 image. Thus in seven observations spanning much of the Cassini mission the bright features were observed to appear, increase in extent, and then disappear. They are referred to as Titan's Magic Islands because of their appearing/disappearing behavior and resemblance in appearance to islands. These transient bright features are not actually islands. The transients were concluded to be most consistent with waves, floating solids, suspended solids, and bubbles. Tides, sea level changes, and seafloor changes are unlikely to be the primary cause of these temporal changes. Whether these temporal changes are also seasonal changes was unclear. The final Cassini RADAR imaging observation of Titan in Apr. 2017 included the region of the Magic Islands. The transient bright features were not present during this observation. The geometry of the observation was such that, had the transients been present, their brightness may have ruled out some of the remaining hypotheses. Their absence however, is less constraining but consistent with their transient nature. Waves, floating solids, suspended solids, and bubbles remain the most likely hypotheses. Other regions of Ligeia Mare were also imaged in the Apr. 2017 observation and no transient features were observed elsewhere in the sea. The specific process responsible for these transient features and the role of seasonal changes in their appearance and disappearance remains an open research question.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.P13D2583H
- Keywords:
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- 6281 Titan;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5470 Surface materials and properties;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS