Is the Xanadu region on Titan an impact basin?

Post by Dr. Mirjam Langhans, GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Germany.

The surface of Titan, Saturn’s largest moon, is subject of great geologic interest, particularly since the arrival of Cassini/Huygens mission in the Saturnian System. Titan’s largest distinct and highly reflective surface feature, named Xanadu, is located close to the equator. The image depicts Xanadu in full extension with a rich diversity of geologic landforms, such as fluvial valleys, mountain ridges and impact craters. Despite the high volume of image data in this region, the geologic history behind Xanadu remains enigmatic to this day.

Geomorphologic map of Xanadu. Data: Cassini SAR data, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). background: Cassini-ISS, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). Inner and outer boundary of the Xanadu Circular Feature (XCF) are highlighted at Western Xanadu (black lines, according to Brown et al. (2011)). Green dots: impact craters listed in Wood et al. (2010) and Neish & Lorenz (2012), red dots: potential impact craters. Fluvial channels are delineated in blue. Dark green: lineations seen in mountain ranges, from Radebaugh et al. (2011). Light green: lineations in mountain ranges (Langhans et al. 2013).

Geomorphologic map of Xanadu. Data: Cassini SAR data, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). background: Cassini-ISS, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). Inner and outer boundary of the Xanadu Circular Feature (XCF) are highlighted at Western Xanadu (black lines, according to Brown et al. (2011)). Green dots: impact craters listed in Wood et al. (2010) and Neish & Lorenz (2012), red dots: potential impact craters. Fluvial channels are delineated in blue. Dark green: lineations seen in mountain ranges, from Radebaugh et al. (2011). Light green: lineations in mountain ranges (Langhans et al. 2013).

Brown et al. (2011) proposed that the contradictory nature of Xanadu’s geology and the stratigraphic relationship to its surroundings could be understood if it were the eroded basin of an ancient impact. The inner and outer boundaries of the suggested impact are detected in near-infrared imagery (Xanadu Circular Feature, XCF, highlighted in the illustration). However, an origin of western Xanadu from a giant impact in the early history of the moon is difficult to confirm given the scarcity of morphologic indications of an impact basin. The basic topographic structure of the landscape is controlled by tectonic processes that likely date back to the early history of Titan. More recently, the surface is intensely reworked and resurfaced by fluvial processes. The lack of geologic indications of a giant impact, such as concentric or radially aligned features speaks against an impact origin of the western Xanadu region. (see Caloris basin on Mercury and its radial valles in Image 3, Image of the Month).

Further Reading:

Brown, R.H. et al (2011). On Titan’s Xanadu region. Icarus, 214, 556-560. Doi: 10.1016/j.icarus.2011.03.018

Radebaugh, J. Et al, (2011) . Regional geomorphology and history of Titan’s Xanadu province. Icarus, 2011, 211, 672-685. Doi: 10.1016/j.icarus.2010.07.022

Langhans M. et al, (2013). Titan’s Xanadu region: Geomorphology and formation scenario. Icarus 2013, 223, 796-803. Doi: 10.1016/j.icarus.2013.01.016

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