Ligeia Mare

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Ligeia Mare

Ligeia Mare from a false-color mosaic of synthetic aperture radar images of Titan's north polar region.
Feature type Mare
Coordinates 79°N 248°W / 79°N 248°W / 79; -248Coordinates: 79°N 248°W / 79°N 248°W / 79; -248
Diameter 500 km[note 1]
Eponym Ligeia

Ligeia Mare /laɪˈdʒiːə ˈmɑriː/[2] is a lake in the north polar region of Titan, the planet Saturn's largest moon. It is the second largest known body of liquid on Titan, after Kraken Mare.[3] Larger than Lake Superior on Earth, it is composed of liquid hydrocarbons (mainly almost pure liquid methane[4]). It is located at 78° N, 249° W, and has been fully imaged by the Cassini spacecraft. It measures roughly 420 km (260 mi) by 350 (217 mi) km across, has a surface area of about 126,000 km2, and a shoreline over 2000 km (1240 mi) in length.[5] Its namesake is Ligeia, one of the sirens in Greek mythology.[3]

Ligeia Mare has two predominant types of coastline, "crenulated" and "subdued".[5] The former is characterized by hummocky, eroded terrain, the latter by lower, smoother topography and the presence of more numerous and longer channels. Crenulated terrain predominates on the eastern and southern sides of the lake; subdued terrain to the west and north.[5] Except in the southeast where the rough topography extends to the coast, hummocky terrain tends to be separated from the shoreline by a more subdued bench. The coast has numerous bays that appear to be flooded river mouths (rias), and unlike at Ontario Lacus there are no visible subaerial delta deposits, possible evidence of a recent sea level rise. In the northeast and northwest sections of the mare, along about a quarter of the total shoreline, there are extensive areas where the depth is less than 5 m, shallow enough for imaging radar to penetrate to the bottom.[5] 2013 radar measurements by Cassini indicate parts of the lake are 170 m deep which implies the liquid must be very pure methane since the radar signal was able to pass right through it. The surface of the lake appears very smooth on radar; it is flat within a few millimeters.[6]

The shorelines of Ligeia Mare and other north polar lakes and maria have been stable over the period of observation by Cassini, in contrast to south polar Ontario Lacus, where there has been significant shoreline recession.[7]

Ligeia Mare is the primary target for the Titan Mare Explorer, a proposed lander mission which would splash down on and then drift about the lake.[8][9] The Titan Lake In-situ Sampling Propelled Explorer (TALISE) is another proposed lander mission which would splash down and navigate across the lake,[10] the major difference between the TiME and TALISE space probes would be a propulsion system.

Gallery

Map of Ligeia Mare by an amateur cartographer
Comparison of Ligeia Mare's size with that of Lake Superior on Earth
Vid Flumina,[1] a river over 400 km long that empties into Ligeia Mare (in the lower center of the image at the top of the page)

Notes

  1. ↑ The USGS web site gives the size as a "diameter", but it is actually the length in the longest dimension.

References

  1. ↑ "Vid Flumina". USGS planetary nomenclature page. USGS. Retrieved 2014-01-01. 
  2. ↑ New Century Cyclopedia of Names
  3. ↑ 3.0 3.1 "Titan maria". Gazetteer of Planetary Nomenclature. USGS Astrogeology Science Center. Retrieved 2012-03-16. 
  4. ↑ "Cassini Spacecraft Reveals Clues About Titan". December 12, 2013. Retrieved 2013-12-18. 
  5. ↑ 5.0 5.1 5.2 5.3 Stofan, E. R.; Lunine, J. I.; Lorenz, R. D.; Kirk, R. L.; Aharonson, O.; Hayes, A. G.; Lucas, A.; Turtle, E. P.; Wall, S. D.; Wood, C. A.; Cassini Radar Team (2012). "Shorelines of Ligeia Mare, Titan". 43rd Lunar and Planetary Science Conference. Lunar and Planetary Institute. Retrieved 2012-03-20. 
  6. ↑ "Cassini Spacecraft Reveals Clues About Titan". December 12, 2013. Retrieved 2013-12-18. 
  7. ↑ Turtle, E. P.; Perry, J. E.; Hayes, A. G.; McEwen, A. S. (2011-02-15). "Shoreline retreat at Titan’s Ontario Lacus and Arrakis Planitia from Cassini Imaging Science Subsystem observations". Icarus 212 (2): 957–959. Bibcode:2011Icar..212..957T. doi:10.1016/j.icarus.2011.02.005. Retrieved 2012-03-25. 
  8. ↑ "Titan Mare Explorer (TiME): The First Exploration of an Extra-Terrestrial Sea". 25 August 2009. Retrieved 2009-11-03. 
  9. ↑ Let's go sailing on lakes of Titan! (November 1, 2009)
  10. ↑ Landau, Elizabeth (2012). "Probe would set sail on a Saturn moon". Retrieved 2012-10-09. 

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