page_title: Odysseus (crater)
section_title: Geology
hierarchical_section_title: Odysseus (crater) / Geology
caption_attribution_description: English: High resolution color map (left) and topography of Saturn's moon Tethys, by the Cassini orboter. Ελληνικά: Υψηλής ανάλυσης έγχρωμος χάρτης (αριστερά) και τοπογραφία (δεξιά) του δορυφόρου του Κρόνου Τηθύς. από τη διαστημοσυσκευή Κασσίνι. Original caption A new view of Tethys A prime objective of the Cassini orbital mission at Saturn is to characterize the nature and evolution of Saturn's extended family of icy satellites. Cassini observations since the beginning of the prime mission in mid-2004 have made possible the first global maps of these diverse bodies. A team of scientists lead by Dr. Paul Schenk (http://www.lpi.usra.edu/lpi/schenk/) at the Lunar and Planetary Institute in Houston has produced the first global color and topographic maps of these satellites. These two views of Tethys show the high-resolution color (at left) and the topography (at right) of the leading, or forward-facing, hemisphere of this 1060-kilometer-diameter (659-mile-diameter) ice-rich satellite. The color map shows the prominent dusky bluish band along the equator, first seen by Voyager in 1980, and shown by Dr. Schenk's team of scientists to be due to the bombardment and alteration of the surface by high energy electrons traveling slower than the satellite's revolution period. These findings were published in the journal Icarus this autumn (Plasma, plumes and rings: Saturn system dynamics as recorded in global color patterns on its midsize icy satellites Paul Schenk, Douglas P. Hamilton, Robert E. Johnson, William B. McKinnon, Chris Paranicas, Jürgen Schmidt and Mark R. Showalter, Icarus, doi:10.1016/j.icarus.2010.08.016). The general reddish tones may be due to the coating of the Tethyean surface by dust-sized particles ejected by Enceladus' south polar plumes. The view at right is a color-coded topographic map of the same region (blues are low, reds are high). The total range of topography shown is 10 kilometers (6 miles) from highest to lowest point. The dominant feature is the 8-kilometer-deep (5-mile-deep) and 440-kilometer-wide (273-mile-deep) Odysseus impact basin at upper left. Straddling the hemisphere like a belt is a previously unknown topographic ridge between 2 and 3 kilometers (1.2 and 1.9 miles) high. To the east of the ridge lies ordinary rolling cratered plains, but between the ridge and Odysseus the surface is scoured and pockmarked. The base resolution of the color map is 400 meters (1312 feet) . The ridge may be a tectonic feature related to the impact event or may be a deposit formed when the ejecta blasted out of Odysseus slammed back onto the surface at high velocity. Visible at bottom right is the globe-circling tectonic canyon, Ithaca Chasma. This map is part of a set of new global topographic maps produced by Dr. Schenk's team for each of Saturn's icy satellites and previewed on-line at http://stereomoons.blogspot.com. The raw data from which this product was developed were retrieved from the Planetary Data System's Cassini archives. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo. (http://ciclops.org). Data processing for this image was performed at the Lunar and Planetary Institute in Houston, Texas.
context_page_description: Odysseus is the largest crater on Saturn's moon Tethys. It is 445 km across, more than 2/5 of the moon's diameter, and is one of the largest craters in the Solar System. It is situated in the western part of the leading hemisphere of the moon—the latitude and longitude of its center are 32.8°N and 128.9°W, respectively. It is named after the Greek hero Odysseus from Homer's the Iliad and the Odyssey.
  Odysseus was discovered by the Voyager 2 spacecraft on 1 September 1981 during its flyby of Saturn.
context_section_description: The Odysseus crater is now quite flat for its size of approximately 450 km or more precisely, its floor conforms to Tethys' spherical shape. This is most likely due to the viscous relaxation of the Tethyan icy crust over geologic time. The floor lies approximately 3 km below the mean radius, while its exterior rim is about 5 km above the mean radius—the relief of 6–9 km is not very high for such a large crater. Inside the crater the rim is composed of arcuate scarps and extends for about 100 km until the floor is reached. There are several graben radiating away from Odysseus, which are 10–20 km wide and hundreds of kilometers long. They are likely to be cracks in the crust created by the impact. The most prominent among them is called Ogygia Chasma.
  The crater must have originally been deep, with a high mountainous rim and towering central peak. Over time the crater floor has relaxed to the spherical shape of the Tethyan surface, and the crater's rim and central peak have collapsed (similar relaxation is apparent on Jupiter's moons Callisto and Ganymede). This indicates that at the time of the Odysseus impact, Tethys must have been sufficiently warm and malleable to allow the topography to collapse; its interior may have even been liquid. If Tethys had been colder and more brittle at the time of impact, the moon might have been shattered, and even if it survived the impact, the topography of the crater would have retained its shape, similarly to the crater Herschel on Mimas.
  The central complex of Odysseus (Scheria Montes) features a central pit-like depression, which is 2–4 km deep. It is surrounded by massifs elevated by 2–3 km above the crater floor, which itself is about 3 km below the average radius.
caption: Color map and elevation map
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