Amphitheater-Headed Valley (Titan)

  • Henrik HargitaiEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-1-4614-9213-9_331-1

Keywords

Geological Timescale Consolidate Material Fluvial Erosion Incised Valley Florida Panhandle 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Definition

Valley characterized by theater-shaped alcoves on Titan.

Category

A type of fluvial valley on Titan

Related Terms

Sapping channel (interpretation)

Description

Generally short and broad, deeply incised valley, which develops amphitheater-shaped heads. They display low albedo on brighter terrain.

Interpretation

Low albedo of valleys is thought to be due to the accumulation of hydrocarbon residue in the valleys. Brighter terrain is thought to be composed of water ice with varying amounts of impurities presumably “washed clean” of hydrocarbons (Griffith et al. 1991; Perron et al. 2006).

Formation

  1. (1)

    Sapping: On Earth, springs from subsurface water may erode loose sediment by underground seepage erosion, causing sapping (undercutting and failure of the ground surface), leading to upslope retreat and the formation of short, stubby tributaries with amphitheater-shaped heads and strong structural control of valley alignment and planform (Sapping Valley) (e.g., Schumm et al. 1995; Perron et al. 2006). This process (methane spring sapping in water ice substrate) has been proposed for stubby drainage channel networks observed near the Huygens Landing Site on Titan (Tomasko et al. 2005). Sapping on Titan requires high amounts of subsurface liquids, “methanifers” (subsurface methane reservoirs) (Langhans et al. 2012*), which is suggested to be present from the observations of lakelike features (Stofan et al. 2007). Seepage erosion also requires horizontally layered material and poorly consolidated sediment to occur. In well-consolidated material, the material must be sufficiently susceptible to weathering, but even terrestrial cases are controversial for seepage erosion in consolidated materials (e.g., Lamb et al. 2006). Titan’s surface materials are thought to have high mechanical strength and low solubility in liquid methane that makes it unlikely that discharge from methane springs could weaken such substrate enough to allow seepage erosion to occur (Perron et al. 2006).

     
  2. (2)

    Sapping and fluvial erosion: Seepage erosion of poorly consolidated material may be combined with fluvial erosion by liquid methane from precipitation, which erodes and transports water ice bedrock (e.g., Lamb et al. 2006).

     
  3. (3)

    Dissolution erosion: Sapping as a primary valley-forming process is still more likely than dissolution erosion on Titan. Dissolution on Titan is possible but unlikely because the solubility of pure water ice in liquid methane or ethane at 94 K is very small. The solubility of pure ammonia ice in liquid methane at 94 K may approach the solubility of calcium carbonate in water on Earth, but there is no evidence of exposed ammonia on the surface (Perron et al. 2006*). However, closed polygonal-walled regions have been identified in more recent images interpreted as karst-like terrain (Malaska et al. 2010).

     

Composition

Titan’s surface and shallow subsurface composition is unknown. The bedrock is most probably made of water ice but is thought to be coated by a large accumulation of photochemically produced hydrocarbon aerosols settling from the atmosphere, of unknown thickness, over geological timescale.

Prominent Examples

Amphitheater-headed channels have been identified near the Huygens Landing Site (Fig. 1) and around 134°W, 50°N, which resemble deeply incised terrestrial canyons (Langhans et al. 2012).
Fig. 1

Amphitheater-headed channels on Titan (arrow). Left: 0436_014143_1786. Right: 0659_021859_9568 (perspective view) at 10°S 192°W, taken from an altitude about 8 km (Tomasko et al. 2005; Langhans et al. 2012). Descent Imager/Spectral Radiometer, Huygens (ESA/NASA/JPL/University of Arizona)

Terrestrial Analog

Valleys in the Florida Panhandle (Schumm et al. 1995).

See Also

References

  1. Griffith CA, Owen T, Wagener R (1991) Titan’s surface and troposphere, investigated with ground-based, near-infrared observations. Icarus 93:362–378CrossRefGoogle Scholar
  2. Lamb MP, Howard AD, Johnson J, Whipple KX, Dietrich WE, Perron JT (2006) Can springs cut canyons into rock? J Geophys Res 111:E07002. doi:10.1029/2005JE002663Google Scholar
  3. Langhans MH, Jaumann R, Stephan K et al (2012) Titan’s fluvial valleys: morphology, distribution, and spectral properties. Planet Space Sci 60:34–51CrossRefGoogle Scholar
  4. Malaska M, Radebaugh J, Lorenz R, Mitchell K, Farr T, Stofan E (2010) Identification of Karst-like terrain on Titan from valley analysis. 41st Lunar Planet Sci Conf, abstract #1544, HoustonGoogle Scholar
  5. Perron JT, Lamb MP, Koven CD, Fung IY, Yager E, Ádámkovics M (2006) Valley formation and methane precipitation rates on Titan. J Geophys Res 111:E11001. doi:10.1029/2005JE002602CrossRefGoogle Scholar
  6. Schumm SA, Boyd KF, Wolff CG, Spitz WJ (1995) A ground-water sapping landscape in the Florida Panhandle. Geomorphology 12:281–297CrossRefGoogle Scholar
  7. Stofan ER et al (2007) The lakes of Titan. Nature 445:61–64CrossRefGoogle Scholar
  8. Tomasko MG et al (2005) Rain, winds and haze during the Huygens probe’s descent to Titan’s surface. Nature 438:765–778CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Planetary Science Research GroupEötvös Loránd University, Institute of Geography and Earth SciencesBudapestHungary