Iapetus (moon)

"Saturn VIII" redirects here. For the rocket, see Saturn C-8.
Iapetus
Iapetus as imaged by the Cassini orbiter in false color, September 2007. Iapetus's unusual coloration can be seen, with the equatorial ridge on the right limb. The large craters Engelier and Gerin are near the bottom.
Discovery
Discovered byG. D. Cassini
Discovery dateOctober 25, 1671
Designations
Designation
Saturn VIII
Pronunciation/aɪˈæpətəs/[1]
Named after
Ἰαπετός Īapetus
AdjectivesIapetian /aɪəˈpiːʃən/[2]
Orbital characteristics
Aphelion3462250 km
Perihelion3659390 km
3560820 km
Eccentricity0.0276812 [3]
79.3215 d
3.26 km/s
Inclination
  • 17.28° (to the ecliptic)
  • 15.47° (to Saturn's equator)
  • 8.13° (to Laplace plane)[4]
Satellite ofSaturn
Physical characteristics
Dimensions1,492.0 × 1,492.0 × 1,424 km [5]
734.4±2.8 km [5][6]
6700000 km2
Mass1.80565×1021 kg[6]
Mean density
1.0887±0.0127 g/cm3[6]
0.223 m/s2 (0.0228 g) (0.138 Moons)
0.573 km/s
79.3215 d
(synchronous)
zero
Albedo0.05–0.5[7]
Temperature90–130 K
10.2–11.9[8]

Iapetus (/aɪˈæpətəs/) is the outermost of Saturn's large moons. With an estimated diameter of 1,469 km (913 mi), it is the third-largest moon of Saturn and the eleventh-largest in the Solar System.[a] Named after the Titan Iapetus, the moon was discovered in 1671 by Giovanni Domenico Cassini.

A relatively low-density body made up mostly of ice, Iapetus is home to several distinctive and unusual features, such as a striking difference in coloration between its leading hemisphere, which is dark, and its trailing hemisphere, which is bright, as well as a massive equatorial ridge running three-quarters of the way around the moon.

  1. ^ "Iapetus". Merriam-Webster.com Dictionary. Merriam-Webster.
  2. ^ Schenk et al. "Saturn's Other Icy Moons: Geologically Complex Worlds." In Schek et al. (2018) Enceladus and the Icy Moons of Saturn, p. 248
  3. ^ Pseudo-MPEC for Saturn VIII Archived February 22, 2012, at the Wayback Machine
  4. ^ Jacobson, R.A. (2009) SAT317 (2009-12-17). "Planetary Satellite Mean Orbital Parameters". JPL/NASA. Retrieved 2011-01-15.{{cite web}}: CS1 maint: numeric names: authors list (link)
  5. ^ a b Cite error: The named reference Roatsch et al. 2009 was invoked but never defined (see the help page).
  6. ^ a b c Jacobson, Robert. A. (1 November 2022). "The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole*". The Astronomical Journal. 164 (5): 199. Bibcode:2022AJ....164..199J. doi:10.3847/1538-3881/ac90c9. S2CID 252992162.
  7. ^ Williams, David R. "Saturnian Satellite Fact Sheet". NASA. Retrieved 2007-11-04.
  8. ^ Cite error: The named reference Observatorio ARVAL was invoked but never defined (see the help page).
  9. ^ Park, Ryan; Chamberlin, Alan B. (2021). "Planetary Satellite Physical Parameters". Jet Propulsion Laboratory. NASA.


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