Saturn Moons Titan & Tethys | NASA Cassini Mission

Saturn Moons Titan & Tethys | NASA Cassini Mission

NASA's Cassini spacecraft arrived in the Saturn system in 2004 and ended its mission in 2017 by deliberately plunging into Saturn's atmosphere. This method was chosen because it is necessary to ensure protection and prevent biological contamination to any of the moons of Saturn thought to offer potential habitability. The Cassini Mission mapped more than 620,000 square miles (1.6 million square kilometers) of liquid lakes and seas on the surface of Saturn's largest moon Titan (visible in foreground). This work was performed with its radar instrument that sent out radio waves and collected a return signal (or echo) that provided information about the terrain and the liquid bodies' depth and composition, along with two imaging systems that could penetrate the moon's thick atmospheric haze.

Titan is larger than the planet Mercury and is the second largest moon in our solar system. Titan is the only moon known to have a dense atmosphere, and the only object in space, other than Earth, where clear evidence of stable bodies of surface liquid has been found. Titan’s subsurface water could be a place to harbor life as we know it, while its surface lakes and seas of liquid hydrocarbons could conceivably harbor life that uses different chemistry than we are used to—that is, life as we do not yet know it. 

Tethys (visible in background) is Saturn's fifth largest moon. This cold, airless and heavily scarred body is very similar to sister moons Dione and Rhea except that Tethys is not as heavily cratered as the other two. This may be because its proximity to Saturn causes more tidal warming, and that warming kept Tethys partially molten longer, erasing or dulling more of the early terrain.

Tethys' density is 0.97 times that of liquid water. This suggests that Tethys is composed almost entirely of water ice plus a small amount of rock.

Tethys has a high reflectivity (or visual albedo) of 1.229 in the visual range, again suggesting a composition largely of water ice. However, this would behave like rock in the Tethyan average temperature of -305 degrees Fahrenheit (-187 degrees Celsius). Many of the crater floors on Tethys are bright, suggesting an abundance of water ice. Also contributing to the high reflectivity is that Tethys is bombarded by Saturn E-ring water-ice particles generated by geysers on Enceladus.

Tethys appeared as a tiny dot to astronomers until the Voyager (1 and 2) encounters in 1980 and 1981. The Voyager images showed a major impact crater and a great chasm. The Cassini spacecraft has added details including a great variety of colors at small scales suggesting a variety of materials not seen elsewhere.

The Cassini-Huygens mission was a cooperative project of NASA, European Space Agency (ESA) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter. The Cassini radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries.

Cassini Mission information:

https://solarsystem.nasa.gov/cassini

Image Credit: NASA / JPL-Caltech / SSI / CICLOPS

Processing: Kevin M. Gill

Image Date: Nov. 26 2009

Image Date: July 1, 2024

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