Ganymede (moon)

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True color image taken by the Galileo probe
Click image for description
Discovered by G. Galilei
S. Marius
Discovery date January 11, 1610
Shortest distance from what it orbits 1,069,200 km (0.007147 AU)
Longest distance from what it orbits 1,071,600 km (0.007163 AU)
Avgdistance from the center of its orbital path 1,070,400 km (0.007155 AU)
How long it takes to complete an orbit 7.15455296 d (0.019588 a)
Average speed 10.880 km/s
Angle above the reference plane
2.21° (to the ecliptic)
0.20° (to Jupiter's equator)
What it orbits Jupiter
Size and other qualities
Average radius 2631.2 km (0.413 Earths)
Surface area 87.0 million km² (0.171 Earths) [1]
Volume 7.6×1010 km³ (0.0704 Earths)
Mass 1.4819×1023 kg (0.025 Earths)
Average density 1.942 g/cm³
Surface gravity 1.428 m/s2 (0.146 g)
Escape velocity 2.741 km/s (6,130 mph)
Rotation period synchronous
Angle at which it turns
(in relation to its orbit)
How much light it reflects 0.43 ± 0.02[2]
Avg. surface temp. ~109 K (−172 °C)
Seeming brightness
("apparent magnitude")
4.61 (opposition) [2]
Pressure trace
Make-up oxygen

Ganymede is the largest moon of Jupiter. It is also the largest moon in the Solar System. Ganymede is larger in diameter than Mercury, but has only about half its mass. Ganymede is much less dense. Ganymede is part of a group called the Galilean Satellites. These also include Io, Europa and Callisto.

Galileo Galilei discovered this moon in 1610.[3] Simon Marius suggested the name Ganymede soon after. In Greek mythology, Ganymede was Zeus' cup-bearer.[4] This name and the names of the other Galilean satellites were not favoured for a long time, and were not put into common use until the mid-20th century. Instead, it is simply referred to by its Roman numeral designation (a system that was introduced by Galileo) as Jupiter III or as the "third satellite of Jupiter".[5] Ganymede is the only Galilean moon of Jupiter named after a male figure.

Structure[change | change source]

Ganymede is composed of roughly equal amounts of silicate rock and water ice.[6] Its body has an iron-rich, liquid core, and an internal ocean that may contain more water than all of Earth's oceans together.[7][8][9][10][11] Its surface has dark regions, with impact craters dated to four billion years ago. This covers about a third of the satellite. Lighter regions, crosscut by grooves and ridges and only slightly less ancient, cover the rest. The cause of the light terrain's disrupted geology is not fully known, but was likely the result of tectonic activity caused by tidal heating.[12]

References[change | change source]

  1. Using the mean radius
  2. 2.0 2.1 Yeomans, Donald K. (2006-Jul-13). "Planetary Satellite Physical Parameters". JPL Solar System Dynamics. Retrieved 2007-11-05.  Check date values in: |date= (help)
  3. Galilei, G.; Sidereus Nuncius (March 13, 1610)
  4. Marius, S.; (1614); Mundus Iovialis anno M.DC.IX Detectus Ope Perspicilli Belgici [1], where he attributes the suggestion to Johannes Kepler
  5. "Satellites of Jupiter". The Galileo Project. Retrieved 2007-11-24. 
  6. Chang, Kenneth (March 12, 2015). "Suddenly, it seems, water is everywhere in Solar System". New York Times. Retrieved March 12, 2015. 
  7. Staff (March 12, 2015). "NASA's Hubble observations suggest underground ocean on Jupiter's largest moon". NASA News. Retrieved 2015-03-15. 
  8. "Jupiter moon Ganymede could have ocean with more water than Earth – NASA". Russia Today (RT). 13 March 2015. Retrieved 2015-03-13. 
  9. Clavin, Whitney (1 May 2014). "Ganymede may harbor 'club sandwich' of oceans and ice". NASA. Jet Propulsion Laboratory. Retrieved 2014-05-01. 
  10. Vance, Steve; Bouffard, Mathieu; Choukroun, Mathieu; Sotina, Christophe (12 April 2014). "Ganymede's internal structure including thermodynamics of magnesium sulfate oceans in contact with ice". Planetary and Space Science. doi:10.1016/j.pss.2014.03.011. Retrieved 2014-05-02. 
  11. Staff (1 May 2014). "Video (00:51) - Jupiter's 'Club Sandwich' Moon". NASA. Retrieved 2014-05-02. 
  12. Tidal heating: the huge force of Jupiter's gravitation deforms the satellite as it swings round its orbit. The orbit is not circular, and this sets up the stresses which cause the tectonic activity.

Other websites[change | change source]