Moon Saturn Iapetus Cai

Iapetus Robert Cai Fall 2014 Introduc8on Photomosaic of Iapetus images taken by Cassini spaceprobe •  Also known as Japetus •  Is third largest moon of Saturn •  In total, Saturn has at least 150 moons and moonlets •  Titan is the largest moon of Saturn, and Rhea is the second largest •  Is eleventh largest moon in Solar System •  Has a drama8c two-­‐tone colora8on •  Was photographed by Cassini spaceprobe in 2007 •  Has a large equatorial ridge Reference: hNp://en.wikipedia.org/wiki/Iapetus_%28moon%29 hNp://en.wikipedia.org/wiki/Saturn Discovery -­‐ Giovanni Domenico Cassini -­‐ Biography Pain8ng of Giovanni Domenico Cassini, discoverer of Iapetus •  Lived from June 8, 1625 un8l September 14, 1712 •  Was born in Perinaldo, Republic of Genova •  Died in Paris, France, at the age of 87 •  Was an Italian astronomer, as well as a mathema8cian, engineer, and astrologer •  Was the principal chair of astronomy at the University of Bologna Reference: hNp://en.wikipedia.org/wiki/Giovanni_Domenico_Cassini Discovery -­‐ Giovanni Domenico Cassini -­‐ Relevance •  Discovered Iapetus on October 25, 1671 •  Also discovered three other moons of Saturn •  Observed the division of the rings of Saturn, later named the Cassini Division •  The Cassini spaceprobe was named a\er him Pain8ng of Giovanni Domenico Cassini, discoverer of Iapetus Reference: hNp://en.wikipedia.org/wiki/Giovanni_Domenico_Cassini Origin of Name Bust of Iapetus, a Titan from Greek mythology •  The moon Iapetus is named a\er the Titan Iapetus, God of Mortality, from Greek mythology •  The Titan Iapetus was: •  The son of the God Uranus and Goddess Gaia •  The father of the Titans Atlas, Prometheus, Epimetheus, and Menoe8us •  The brother of the Titan Cronus •  The moon Iapetus’ alterna8ve name is Saturn VIII Reference: hNp://en.wikipedia.org/wiki/Iapetus_%28mythology%29 Orbital Characteris8cs •  Semi-­‐major axis (longest diameter of Iapetus’ orbit): 3,560,820 km •  Eccentricity (amount of devia8on of Iapetus’ orbit from a perfect circle): 0.0286125 •  Orbital period (amount of 8me for one complete Iapetus orbit): 79.3215 days •  Average orbital speed (average speed of Iapetus’ orbit): 3.26 km/s •  Inclina;on (angle of Iapetus’ orbital plane with respect to a reference plane): 17.28° (to the eclip8c); 15.47° (to Saturn’s equator), 8.13° (to Laplace plane) •  Satellite of: Saturn Reference: hNp://en.wikipedia.org/wiki/Iapetus_%28moon%29 Physical Characteris8cs -­‐ Stats • 
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Dimensions: 1,492.0 x 1,492.0 x 1,424 km Mean radius: 734.5 + 2.8 km Surface area: 6,700,000 km2 Mass: (1.805635 + 0.000375) x 1021 kg Mean density: 1.088 + 0.013 g/cm3 Surface gravity (gravita8onal accelera8on at Iapetus’ surface): 0.224 m/s2 Escape velocity (speed needed to overcome Iapetus’ gravita8onal aNrac8on): 0.573 km/s Rota;on period (amount of 8me for one complete revolu8on of Iapetus around its rota8onal axis): 79.3215 days Axial ;lt (angle between Iapetus’ rota8onal axis and orbital axis): zero Albedo (reflec8ng power of Iapetus’ surface): 0.05 – 0.5 Temperature: 90 – 130 K Apparent magnitude: 10.2 – 11.9 Reference: hNp://en.wikipedia.org/wiki/Iapetus_%28moon%29 Physical Characteris8cs -­‐ Descrip8ons Mosaic of Iapetus taken by Cassini spaceprobe •  Two-­‐tone colora8on –  Cassini Regio: dark region of Iapetus –  Roncevaux Terra, Saragossa Terra: bright regions of Iapetus •  Shape –  O\en characterized as walnut-­‐
shaped –  Contains bulging equatorial area due to ridge •  Equatorial ridge –  About 1,300 km long, 20 km wide, and 13 km high –  Located along the center of Cassini Regio Reference: hNp://en.wikipedia.org/wiki/Iapetus_%28moon%29 Physical Characteris8cs – Equatorial Ridge •  Two theories regarding the origin of the equatorial ridge: Photo showing close view of equatorial ridge –  The ridge may have formed at an earlier 8me when Iapetus rotated much faster than it currently does –  The ridge may have formed out of material le\ from the collapse of a ring at an earlier 8me Reference: hNp://solarsystem.nasa.gov/planets/profile.cfm?Object=Iapetus Orbit •  Overall, Iapetus has an unusually distant and inclined orbit Side view of Iapetus’ orbit shows unusually high inclina8on Polar view of Iapetus’ orbit shows unusually high distance from Saturn Reference: hNp://en.wikipedia.org/wiki/Iapetus_%28moon%29 Explora8on – Cassini spaceprobe Digital image of Cassini spaceprobe •  Launched on October 15, 1997 a\er about two decades of development •  Entered orbit around Saturn on July 1, 2004 •  Has imaged Iapetus mul8ple 8mes from moderate distances •  Has imaged Iapetus once from close distance on September 10, 2007 Reference: hNp://en.wikipedia.org/wiki/Cassini%E2%80%93Huygens Bibliography •  hNp://en.wikipedia.org/wiki/Iapetus_
%28moon%29 •  hNp://en.wikipedia.org/wiki/
Giovanni_Domenico_Cassini •  hNp://en.wikipedia.org/wiki/Iapetus_
%28mythology%29 •  hNp://en.wikipedia.org/wiki/Cassini
%E2%80%93Huygens