page_title: Tholin
section_title: Rhea
hierarchical_section_title: Tholin / Occurrence / Moons / Rhea
caption_attribution_description: English: Saturn's Moons: What a Difference a Decade Makes December 9, 2014 http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18437 Color Maps of Rhea - 2014 November 4, 2014 http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18438 This set of global, color mosaics of Saturn's moon Rhea was produced from images taken by NASA's Cassini spacecraft during its first ten years exploring the Saturn system. These are the first global color maps of these moons produced from the Cassini data. The most obvious feature on the maps is the difference in color and brightness between the two hemispheres. The darker colors on the trailing hemispheres are thought to be due to alteration by magnetospheric particles and radiation striking those surfaces. The lighter-colored leading hemisphere is coated with icy dust from Saturn's E-ring, formed from tiny particles ejected from Enceladus' south pole. These satellites are all being painted by material erupted by neighboring Enceladus. The colors shown in these global mosaics are enhanced, or broader, relative to human vision, extending into the ultraviolet and infrared range. Resolution on Rhea in the maps is 400 meters per pixel. Image selection, radiometric calibration, geographic registration and photometric correction, as well as mosaic selection and assembly were performed by Paul Schenk at the Lunar and Planetary Institute. Original image planning and targeting for Saturn's icy moons were performed by Tilman Denk (Frei Universitat, Berlin) and Paul Helfenstein (Cornell University, Ithaca, New York). The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. 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. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org
context_page_description: Tholins are a wide variety of organic compounds formed by solar ultraviolet or cosmic rays irradiation of simple carbon-containing compounds such as carbon dioxide, methane or ethane, often in combination with nitrogen or water. Tholins are disordered polymer-like materials made of repeating chains of linked subunits and complex combinations of functional groups. Tholins do not form naturally on modern-day Earth, but they are found in great abundance on the surfaces of icy bodies in the outer Solar System, and as reddish aerosols in the atmosphere of outer Solar System planets and moons.
  In the presence of water, tholins can be raw materials for prebiotic chemistry, i.e. the non-living chemistry that forms the basic chemicals which form life. Their existence has implications for the origins of life on Earth, and possibly on other planets. As particles in an atmosphere, tholins scatter light, and can affect habitability.
context_section_description: The extensive dark areas on the trailing hemisphere of Saturn's moon Rhea are thought to be deposited tholins.
caption: The trailing hemisphere of Saturn's moon Rhea is covered with tholins.
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