Presentation on theme: "Joel Schwartz Northwestern Physics & Astronomy May 13 th, 2013 Voyager 1 Image. Saturn. Nov 1980. LPI. 3 May 2013."— Presentation transcript:
Joel Schwartz Northwestern Physics & Astronomy May 13 th, 2013 Voyager 1 Image. Saturn. Nov LPI. 3 May 2013.
Moons of Solar System. NASA SSE. 3 May 2013.
Discovery All three satellites were first observed by Giovanni Cassini. Iapetus: October 25 th, 1671 Rhea: December 23 rd, 1672 Tethys: March 21 st, 1684 These moons & Dione were originally called Sidera Lodoicea (The Stars of Louis) by Cassini, after Louis XIV.
Orbital Locations Orbital Diagram of Saturn Moons U. Cincinnati Physics- Gas Giants. 4 May 2013.
Etymology Associated with siblings of Kronos, as suggested by John Herschel. Tethys: Sister of Kronos & wife of Oceanus. Linked to rivers & water. Rhea: Wife/Sister of Kronos. Referred to as the “Mother of the Gods.” Iapetus: Brother to Kronos; father of Atlas & Prometheus. Considered the “Father of the Human Race” by the ancient Greeks.
Greek Titans Greek Titans (Various). Wikipedia. 4 May 2013
Previous/Current Space Missions Pioneer 11: August-September 1979 Voyager 1: November 1980 (no Iapetus flyby) Voyager 2: August 1981 Cassini-Huygens: July 2004 & onward Initial images by Voyager 1 & 2, then more detailed photography by Cassini- Huygens.
Tethys (Saturn III) Radius: 531.1km Density: 985 kg/m^3 Vis. Geo. Albedo: 0.8 Semimajor Axis: 294.7k km Period: days (tidally locked) Inclination: 1.88° Cassini Image. Tethys. National Space Science Data Center. 4 May 2013.
Tethys (cont.) Heavily cratered, but not to the extent of Rhea. Largely water-ice with small amounts of rock. Gravitationally holds Telesto & Calypso. Quite noticeable is Odysseus Crater, prominent in the Western Hemisphere. Cassini Image. Tethys with Odysseus Crater. NASA SSE. 4 May 2013
Tethys (cont.) Has a high visual geometric albedo. Is bombarded by water-ice particles from geysers on Enceladus. Has the Ithaca Chasma running roughly from the north to south pole. Voyager 2 Image. Tethys with Ithaca Chasma. 26 Aug NSSDC. 4 May 2013.
Composite Spectroscopy Data A Pair of Pac-Men. 26 Nov NASA SSE. 4 May 2013.
Rhea (Saturn V) Radius: 763.8km Density: 1240 kg/m^3 Vis. Geo. Albedo: 0.7 Semimajor Axis: k km Period: days (tidally locked) Inclination: 0.35° Cassini Image. Portrait of a Lady. 10 Mar NASA SSE. 4 May 2013.
Rhea (cont.) Cold body with tenuous atmosphere; similar to Tethys. Density suggests ¾ water-ice, ¼ rock, and homogeneous. Due to distance from Saturn, Rhea does not receive significant tidal heating effects. Voyager 1 Image. Rhea Mosaic. Nov NSSDC. 3 May 2013.
Rhea (cont.) Large amount of craters, which can be subdivided into two regions: Heavy cratered bright terrain with diameters above 40km. Polar & equatorial areas with smaller diameter craters. “Wispy” subsidence fractures also present. Voyager 1 Image. Rhea, Enhanced. 12 Nov NSSDC. 4 May 2013.
False-Color Imaging Saturn-facing view of Rhea from 35,000km. Demonstrates hemispherical color and albedo differences. Reddish hues near poles identify composition changes (multiple explanations). Cassini Image. False-Color Rhea. 2 Mar NSSDC. 4 May 2013.
Iapetus (Saturn VIII) Radius: 734.5km Density: 1090 kg/m^3 Vis. Geo. Albedo: 0.05 to 0.5 Semimajor Axis: k km Period: days (tidally locked) Inclination: 14.72° Voyager 2 Image. Iapetus. Aug NASA SSE. 3 May 2013.
Iapetus (cont.) Similar to Tethys, density suggests composition of mostly water-ice. Overall shape is not ellipsoidal, but rather “walnut.” Has two recognizable features: ridge at equator & dual albedo. Cassini Image. Iapetus, Equatorial Ridge. NSSDC. 4 May 2013.
Iapetus (cont.) Although 3 rd largest moon of Saturn, Iapetus orbits much further out than Titan. Inclination is highest of all regular satellites, giving best view of Saturn’s rings. Pattern of craters follows albedo: heavy in bright region, less elsewhere (Turgis seen here.) Cassini Image. Iapetus, Engelier Crater. NSSDC. 3 May 2013.
Equatorial Ridge Around equator, Iapetus has a chain of ~20km mountains. These break up on side facing away from Saturn into the bright Voyager Mountains. Multiple proposed theories for ridge. Cassini Image. Voyager Mountains. 10 Sep NASA SSE. 4 May 2013.
Two-Tone Albedo Cassini Image. Global View of Dichotomy. 27 Dec NASA SSE. 4 May 2013.
Future Mission Prospects Tethys, Rhea, & Iapetus are all devoid of many life-harboring properties. Furthermore, there are other bodies in the Solar System which should have preferential scientific importance. Marginally, Iapetus does have unique albedo & ridge features. Even still, the prospect for future missions is understandably low.