Cassini Imaging Science: Initial Results on Phoebe and Iapetus

Porco, C. C.; Baker, Emily J.; Barbara, J.; Beurle, K.; Brahic, A.; Burns, Joseph A.; Charnoz, S.; Cooper, Nicholas J.; Dawson, D. D.; Genio, Anthony D. Del; Denk, T.; Dones, L.; Dyudina, Ulyana A.; Evans, Michael; Giese, B.; Grazier, Kevin R.; Helfenstein, P.; Ingersoll, Andrew P.; Jacobson, R. A.; Johnson, T. V.; McEwen, A. S.; Murray, C. D.; Neukum, G.; Owen, W. M.; Perry, Jason; Roatsch, Thomas; Spitale, J. N.; Squyres, S. W.; Thomas, P. C.; Tiscareno, Matthew S.; Turtle, E. P.; Vasavada, A. R.; Veverka, J.; Wagner, Roland; West, Robert A.

doi:10.1126/science.1107981

Cited by 179 publications

(156 citation statements)

References 20 publications

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“…Spectroscopic studies show a large diversity of colors (ranging from gray to very red ) among observed irregular satellites of four outer planets (Cruikshank 1980;Degewij et al 1980;Dumas et al 1998;Brown 2000;Sykes et al 2000;Grav et al 2003Porco et al 2005). This diversity would be difficult to understand if irregular satellites were captured from a local and dynamically cold population of planetesimals at the planet's heliocentric position, because in such a case the colors should be homogeneous (reflecting the local composition) and there should exist a clear color gradient of irregular satellites with heliocentric distance (i.e., from Jupiter to Neptune).…”

Section: Introductionmentioning

confidence: 99%

Capture of Irregular Satellites during Planetary Encounters

2007

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More than 90 irregular moons of the Jovian planets have recently been discovered. These moons are an enigmatic part of the solar system inventory. Their origin, which is intimately linked with the origin of the planets themselves, has yet to be adequately explained. Here we investigate the possibility that the irregular moons were captured from the circumsolar planetesimal disk by three-body gravitational reactions. These reactions may have been a frequent occurrence during the time when the outer planets migrated within the planetesimal disk. We propose a new model for the origin of irregular satellites in which these objects are captured from the planetesimal disk during encounters between the outer planets themselves in the model for outer planet migration advocated by Tsiganis and collaborators. Through a series of numerical simulations we show that nearby planetesimals can be deflected into planet-bound orbits during close encounters between planets, and that the overall efficiency of this capture process is large enough to produce populations of observed irregular satellites at Saturn, Uranus, and Neptune. The orbits of captured objects are broadly similar to those of known distant satellites. Jupiter, which typically does not have close encounters with other planets in the model of Tsiganis and coworkers, must have acquired its irregular satellites by a different mechanism. Alternatively, the migration model should be modified to accommodate Jupiter's encounters. Moreover, we find that the original size-frequency distribution of the irregular moons must have significantly evolved by collisions to produce their present populations. Our new model may also provide a plausible explanation for the origin of Neptune's large moon Triton.

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Section: Introductionmentioning

confidence: 99%

Capture of Irregular Satellites during Planetary Encounters

2007

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“…Cassini discovered that dark material, probably from Phoebe which orbits at 215 Saturn radii, is deposited onto the surface and is then "thermally segregated" -it warms in sunlight, is mobilized and then re deposited on colder areas (Tosi et al 2010). Iapetus also has an equatorial ridge rising 10 km, with peaks up to 20 km, above the moon's surface (Porco et al 2005), possibly from earlier rapid rotation or aggregation from a collapsed ring. Phoebe as a source is made more likely by the discovery using Spitzer Space Telescope data of a disc of material extending between at least 128 and 207 Saturn radii, associated with Phoebe (Verbiscer et al 2009).…”

Section: Icy Satellitesmentioning

confidence: 99%

Cassini–Huygens: Saturn, rings and moons

Coates¹

2017

Astronomy &Amp; Geophysics

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“…Himalia and Phoebe by Cassini (Porco et al 2003(Porco et al , 2005, or Nereid by Voyager-2 (Thomas et al 1991). Recently, thermal emission data obtained with the MIPS camera of the Spitzer Space Telescope (Rieke et al 2004) and the PACS camera of the Herschel Space Observatory (Poglitsch et al 2010) also provided independent size and albedo estimates for Sycorax (Lellouch et al 2013) and Nereid ).…”

Section: Introductionmentioning

confidence: 99%

Properties of the Irregular Satellite System around Uranus Inferred from K2, Herschel, and Spitzer Observations

Farkas-Takács

Kiss

Pál

et al. 2017

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In this paper we present visible range light curves of the irregular Uranian satellites Sycorax, Caliban, Prospero, Ferdinand and Setebos taken with Kepler Space Telescope in the course of the K2 mission. Thermal emission measurements obtained with the Herschel/PACS and Spitzer/MIPS instruments of Sycorax and Caliban were also analysed and used to determine size, albedo and surface characteristics of these bodies. We compare these properties with the rotational and surface characteristics of irregular satellites in other giant planet systems and also with those of main belt and Trojan asteroids and trans-Neptunian objects. Our results indicate that the Uranian irregular satellite system likely went through a more intense collisional evolution than the irregular satellites of Jupiter and Saturn. Surface characteristics of Uranian irregular satellites seems to resemble the Centaurs and trans-Neptunian objects more than irregular satellites around other giant planets, suggesting the existence of a compositional discontinuity in the young Solar system inside the orbit of Uranus.

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Cassini Imaging Science: Initial Results on Phoebe and Iapetus

Cited by 179 publications

References 20 publications

Capture of Irregular Satellites during Planetary Encounters

Capture of Irregular Satellites during Planetary Encounters

Cassini–Huygens: Saturn, rings and moons

Properties of the Irregular Satellite System around Uranus Inferred from K2, Herschel, and Spitzer Observations

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