# Moons of Jupiter

(Redirected from Jupiter's moons)

A montage of Jupiter and its four largest moons (distance and sizes not to scale)

There are 79 known moons of Jupiter.[1][2][3] The most massive of the moons are the four Galilean moons, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. From the end of the 19th century, dozens of much smaller Jovian moons have been discovered and have received the names of lovers or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 75 known moons and the rings together composing just 0.003% of the total orbiting mass.

Of Jupiter's moons, eight are regular satellites with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter's equatorial plane. The Galilean satellites are nearly spherical in shape due to their planetary mass, and so would be considered at least dwarf planets if they were in direct orbit around the Sun. The other four regular satellites are much smaller and closer to Jupiter; these serve as sources of the dust that makes up Jupiter's rings. The remainder of Jupiter's moons are irregular satellites whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were probably captured by Jupiter from solar orbits. Twenty-two of the irregular satellites have not yet been officially named.

## Characteristics

The Galilean moons. From left to right, in order of increasing distance from Jupiter: Io; Europa; Ganymede; Callisto.

The physical and orbital characteristics of the moons vary widely. The four Galileans are all over 3,100 kilometres (1,900 mi) in diameter; the largest Galilean, Ganymede, is the ninth largest object in the Solar System, after the Sun and seven of the planets, Ganymede being larger than Mercury. All other Jovian moons are less than 250 kilometres (160 mi) in diameter, with most barely exceeding 5 kilometres (3.1 mi).[note 1] Their orbital shapes range from nearly perfectly circular to highly eccentric and inclined, and many revolve in the direction opposite to Jupiter's spin (retrograde motion). Orbital periods range from seven hours (taking less time than Jupiter does to spin around its axis), to some three thousand times more (almost three Earth years).

## Origin and evolution

The relative masses of the Jovian moons. Those smaller than Europa are not visible at this scale, and combined would only be visible at 100× magnification!

Jupiter's regular satellites are believed to have formed from a circumplanetary disk, a ring of accreting gas and solid debris analogous to a protoplanetary disk.[4][5] They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history.[4][6]

Simulations suggest that, while the disk had a relatively high mass at any given moment, over time a substantial fraction (several tenths of a percent) of the mass of Jupiter captured from the solar nebula was passed through it. However, only 2% of the proto-disk mass of Jupiter is required to explain the existing satellites.[4] Thus there may have been several generations of Galilean-mass satellites in Jupiter's early history. Each generation of moons might have spiraled into Jupiter, because of drag from the disk, with new moons then forming from the new debris captured from the solar nebula.[4] By the time the present (possibly fifth) generation formed, the disk had thinned so that it no longer greatly interfered with the moons' orbits.[6] The current Galilean moons were still affected, falling into and being partially protected by an orbital resonance with each other, which still exists for Io, Europa, and Ganymede. Ganymede's larger mass means that it would have migrated inward at a faster rate than Europa or Io.[4]

The outer, irregular moons are thought to have originated from captured asteroids, whereas the protolunar disk was still massive enough to absorb much of their momentum and thus capture them into orbit. Many are believed to have broken up by mechanical stresses during capture, or afterward by collisions with other small bodies, producing the moons we see today.[7]

## Discovery

Jupiter and the Galilean moons through a 25 cm (10 in) Meade LX200 telescope.
The number of moons known for each of the four outer planets up to October 2019. Jupiter currently has 79 known satellites.

Chinese historian Xi Zezong claimed that the earliest record of a Jovian moon (Ganymede or Callisto) was a note by Chinese astronomer Gan De of an observation around 364 BC regarding a "reddish star".[8] However, the first certain observations of Jupiter's satellites were those of Galileo Galilei in 1609.[9] By January 1610, he had sighted the four massive Galilean moons with his 20× magnification telescope, and he published his results in March 1610.[10]

Simon Marius had independently discovered the moons one day after Galileo, although he did not publish his book on the subject until 1614. Even so, the names Marius assigned are used today: Ganymede; Callisto; Io; and Europa.[11] No additional satellites were discovered until E. E. Barnard observed Amalthea in 1892.[12]

With the aid of telescopic photography, further discoveries followed quickly over the course of the 20th century. Himalia was discovered in 1904,[13] Elara in 1905,[14] Pasiphae in 1908,[15] Sinope in 1914,[16] Lysithea and Carme in 1938,[17] Ananke in 1951,[18] and Leda in 1974.[19] By the time that the Voyager space probes reached Jupiter, around 1979, 13 moons had been discovered, not including Themisto, which had been observed in 1975,[20] but was lost until 2000 due to insufficient initial observation data. The Voyager spacecraft discovered an additional three inner moons in 1979: Metis; Adrastea; and Thebe.[21]

No additional moons were discovered for two decades, but between October 1999 and February 2003, researchers found another 34 moons using sensitive ground-based detectors.[22] These are tiny moons, in long, eccentric, generally retrograde orbits, and averaging 3 km (1.9 mi) in diameter, with the largest being just 9 km (5.6 mi) across. All of these moons are thought to have been captured asteroidal or perhaps comet bodies, possibly fragmented into several pieces.[23][24]

By 2015, a total of 15 additional moons were discovered.[24] Two more were discovered in 2016 by the team led by Scott S. Sheppard at the Carnegie Institution for Science, bringing the total to 69.[25] On 17 July 2018, the International Astronomical Union confirmed that Sheppard's team had discovered ten more moons around Jupiter, bringing the total number to 79.[26] Among these is Valetudo, which has a prograde orbit, but crosses paths with several moons that have retrograde orbits, making an eventual collision—at some point on a billions of years timescale—likely.[27]

Additional tiny moons likely exist but remain undiscovered, as they are very difficult for astronomers to detect.[3]

## Naming

Galilean moons around Jupiter   Jupiter ·   Io ·   Europa ·   Ganymede ·   Callisto
Orbits of Jupiter's inner moons within its rings

The Galilean moons of Jupiter (Io, Europa, Ganymede, and Callisto) were named by Simon Marius soon after their discovery in 1610.[28] However, these names fell out of favor until the 20th century. The astronomical literature instead simply referred to "Jupiter I", "Jupiter II", etc., or "the first satellite of Jupiter", "Jupiter's second satellite", and so on.[28] The names Io, Europa, Ganymede, and Callisto became popular in the mid-20th century,[29] whereas the rest of the moons remained unnamed and were usually numbered in Roman numerals V (5) to XII (12).[30][better source needed] Jupiter V was discovered in 1892 and given the name Amalthea by a popular though unofficial convention, a name first used by French astronomer Camille Flammarion.[22]

The other moons were simply labeled by their Roman numeral (e.g. Jupiter IX) in the majority of astronomical literature until the 1970s.[31] In 1975, the International Astronomical Union's (IAU) Task Group for Outer Solar System Nomenclature granted names to satellites V–XIII,[32] and provided for a formal naming process for future satellites still to be discovered.[32] The practice was to name newly discovered moons of Jupiter after lovers and favorites of the god Jupiter (Zeus) and, since 2004, also after their descendants.[33] All of Jupiter's satellites from XXXIV (Euporie) onward are named after descendants of Jupiter or Zeus,[33] except LIII (Dia), named after a lover of Jupiter. Names ending with "a" or "o" are used for prograde irregular satellites (the latter for highly inclined satellites), and names ending with "e" are used for retrograde irregulars.[34] Some of the most recently confirmed moons have not received names.

Some asteroids share the same names as moons of Jupiter: 9 Metis, 38 Leda, 52 Europa, 85 Io, 113 Amalthea, 239 Adrastea. Two more asteroids previously shared the names of Jovian moons until spelling differences were made permanent by the IAU: Ganymede and asteroid 1036 Ganymed; and Callisto and asteroid 204 Kallisto.

## Groups

The orbits of Jupiter's irregular satellites, and how they cluster into groups: by semi-major axis (the horizontal axis in Gm); by orbital inclination (the vertical axis); and orbital eccentricity (the yellow lines). The relative sizes are indicated by the circles.

### Regular satellites

These have prograde and nearly circular orbits of low inclination and are split into two groups:

• Inner satellites or Amalthea group: Metis, Adrastea, Amalthea, and Thebe. These orbit very close to Jupiter; the innermost two orbit in less than a Jovian day. The latter two are respectively the fifth and seventh largest moons in the Jovian system. Observations suggest that at least the largest member, Amalthea, did not form on its present orbit, but farther from the planet, or that it is a captured Solar System body.[35] These moons, along with a number of as-yet-unseen inner moonlets, replenish and maintain Jupiter's faint ring system. Metis and Adrastea help to maintain Jupiter's main ring, whereas Amalthea and Thebe each maintain their own faint outer rings.[36][37]
• Main group or Galilean moons: Io, Europa, Ganymede and Callisto. They are some of the largest objects in the Solar System outside the Sun and the eight planets in terms of mass and are larger than any known dwarf planet. Ganymede exceeds even the planet Mercury in diameter, though is less massive. They are respectively the fourth-, sixth-, first-, and third-largest natural satellites in the Solar System, containing approximately 99.997% of the total mass in orbit around Jupiter, while Jupiter is almost 5,000 times more massive than the Galilean moons.[note 2] The inner moons are in a 1:2:4 orbital resonance. Models suggest that they formed by slow accretion in the low-density Jovian subnebula—a disc of the gas and dust that existed around Jupiter after its formation—which lasted up to 10 million years in the case of Callisto.[38] Several are suspected of having subsurface oceans.

### Irregular satellites

Orbits of Jupiter's irregular moons, color-coded by their group

The irregular satellites are substantially smaller objects with more distant and eccentric orbits. They form families with shared similarities in orbit (semi-major axis, inclination, eccentricity) and composition; it is believed that these are at least partially collisional families that were created when larger (but still small) parent bodies were shattered by impacts from asteroids captured by Jupiter's gravitational field. These families bear the names of their largest members. The identification of satellite families is tentative, but the following are typically listed:[39][40][41]

• Themisto[40] is the innermost irregular moon and is not part of a known family.[39]
• The Himalia group is spread over barely 1.4 Gm in semi-major axes, 1.6° in inclination (27.5 ± 0.8°), and eccentricities between 0.11 and 0.25. It has been suggested that the group could be a remnant of the break-up of an asteroid from the asteroid belt.[40]
• Carpo is another prograde moon and is not part of a known family. It has the highest inclination of all of the prograde moons.[39]
• Valetudo, reported 2018, is the outermost prograde moon and is not part of a known family.[39] It has a prograde orbit, but it crosses paths with several moons that have retrograde orbits and may in the future collide with them.[42]
• Retrograde satellites: inclinations (°) vs. eccentricities, with Carme's (orange) and Ananke's (yellow) groups identified. Data as of 2009.
• The Carme group is spread over only 1.2 Gm in semi-major axis, 1.6° in inclination (165.7 ± 0.8°), and eccentricities between 0.23 and 0.27. It is very homogeneous in color (light red) and is believed to have originated from a D-type asteroid progenitor, possibly a Jupiter Trojan.[23]
• The Ananke group has a relatively wider spread than the previous groups, over 2.4 Gm in semi-major axis, 8.1° in inclination (between 145.7° and 154.8°), and eccentricities between 0.02 and 0.28. Most of the members appear gray, and are believed to have formed from the breakup of a captured asteroid.[23]
• The Pasiphae group is quite dispersed, with a spread over 1.3 Gm, inclinations between 144.5° and 158.3°, and eccentricities between 0.25 and 0.43.[23] The colors also vary significantly, from red to grey, which might be the result of multiple collisions. Sinope, sometimes included in the Pasiphae group,[23] is red and, given the difference in inclination, it could have been captured independently;[40] Pasiphae and Sinope are also trapped in secular resonances with Jupiter.[43]

## List

The moons of Jupiter are listed below by orbital period. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in bold. These are the four Galilean moons, which are comparable in size to the Moon. The other moons are much smaller, with the least massive Galilean moon being more than 7000 times more massive than the most massive of the other moons. The irregular captured moons are shaded light gray when prograde and dark gray when retrograde. All orbits are based on the estimated orbit on the Julian date 2458200, or 23 March 2018. As several moons of Jupiter are currently lost, these orbital elements may be only rough approximations. As of 2018, seven satellites are considered to be lost. These are S/2003 J 2, S/2003 J 4, S/2003 J 9, S/2003 J 10, S/2003 J 12, S/2003 J 16, and S/2003 J 23. A number of other moons have only been observed for a year or two, but have decent enough orbits to be easily measurable even in 2018.

Key

Galilean moons

Order
[note 3]
Label
[note 4]
Name
Pronunciation Image Abs.
magn.
Diameter (km)[note 5] Mass
(×1016 kg)
Semi-major axis
(km)[44]
Orbital period (d)
[44][note 6]
Inclination
(°)[44]
Eccentricity
[39]
Discovery
year
[22]
Discoverer[22] Group
[note 7]
1 XVI Metis /ˈmtɪs/
10.5 43
(60 × 40 × 34)
≈ 3.6 128852 +0.2988
(+7h 10m 16s)
2.226 0.0077 1979 Synnott
(Voyager 1)
Inner
12.0 16.4
(20 × 16 × 14)
≈ 0.2 129000 +0.3023
(+7h 15m 21s)
2.217 0.0063 1979 Jewitt
(Voyager 2)
Inner
3 V Amalthea /æməlˈθə/[45]
7.1 167
(250 × 146 × 128)
208 181366 +0.5012
(+12h 01m 46s)
2.565 0.0075 1892 Barnard Inner
4 XIV Thebe /ˈθb/
9.0 98.6
(116 × 98 × 84)
≈ 43 222452 +0.6778
(+16h 16m 02s)
2.909 0.0180 1979 Synnott
(Voyager 1)
Inner
5 I Io /ˈ/
−1.7 3643.2
(3660 × 3637 × 3631)
8931900 421700 +1.7691 0.050[46] 0.0041 1610 Galilei Galilean
6 II Europa /jʊəˈrpə/[47]
−1.4 3121.6 4800000 671034 +3.5512 0.471[46] 0.0094 1610 Galilei Galilean
7 III Ganymede /ˈɡænɪmd/[48][49]
−2.1 5262.4 14819000 1070412 +7.1546 0.204[46] 0.0011 1610 Galilei Galilean
8 IV Callisto /kəˈlɪst/
−1.2 4820.6 10759000 1882709 +16.689 0.205[46] 0.0074 1610 Galilei Galilean
9 XVIII Themisto /θɪˈmɪst/
12.9 9 ≈ 0.069 7396100 +129.95 45.281 0.2522 1975/2000 Kowal & Roemer/
Sheppard et al.
Themisto
10 XIII Leda /ˈldə/
12.7 21.5 ≈ 0.6 11174800 +241.33 28.414 0.1628 1974 Kowal Himalia
11 VI Himalia /hɪˈmliə/
7.9 139.6
(150 × 120)
420 11394100 +248.47 30.214 0.1510 1904 Perrine Himalia
12 LXXI Ersa /ˈɜːrsə/ 15.9 3 ≈ 0.0045 11453000 +250.40 30.606 0.0944 2018 Sheppard et al. Himalia
13 LXV Pandia /pænˈdə/ 16.2 3 ≈ 0.0045 11494800 +251.77 28.155 0.1800 2017 Sheppard et al. Himalia
14 VII Elara /ˈɛlərə/
9.6 79.9 ≈ 87 11698000 +258.48 29.974 0.1776 1905 Perrine Himalia
15 X Lysithea /lˈsɪθiə/
11.2 42.2 ≈ 6.3 11701100 +258.58 26.502 0.1353 1938 Nicholson Himalia
16 LIII Dia /ˈdə/
16.3 4 ≈ 0.009 12221000 +276.00 26.965 0.2383 2000 Sheppard et al. Himalia
17 XLVI Carpo /ˈkɑːrp/ 16.1 3 ≈ 0.0045 16700600 +440.91 53.558 0.5166 2003 Sheppard et al. Carpo
18 (lost) S/2003 J 12 17.0 1 ≈ 0.00015 17740000
(28717400±1136900)[50]
−482.69
(–944.29)[50]
142.686
(152.5±1.3)[50]
0.4449
(0.402±0.044)[50]
2003 Sheppard et al. Ananke? (unconfirmed)
19 LXII Valetudo /vælɪˈtjd/ 16.9 1 ≈ 0.00015 18928100 +532.01 34.015 0.2219 2016 Sheppard et al. Valetudo
20 XXXIV Euporie /ˈjpər/
16.3 2 ≈ 0.0015 19179700 −542.65 144.856 0.0901 2001 Sheppard et al. Ananke
21 LV S/2003 J 18 16.5 2 ≈ 0.0015 20219700 −587.38 146.376 0.1048 2003 Gladman et al. Ananke
22 XXII Harpalyke /hɑːrˈpælɪk/
15.9 4 ≈ 0.009 20429800 −596.56 146.980 0.1719 2000 Sheppard et al. Ananke
23 XXX Hermippe /hərˈmɪp/
15.6 4 ≈ 0.009 20564800 −602.48 150.596 0.1797 2001 Sheppard et al. Ananke
24 LXVIII S/2017 J 7 16.6 2 ≈ 0.0015 20571500 −602.77 143.439 0.2147 2017 Sheppard et al. Ananke
25 XXXIII Euanthe /jˈænθ/
16.4 3 ≈ 0.0045 20572300 −602.81 143.649 0.1399 2001 Sheppard et al. Ananke
26 XXIX Thyone /θˈn/
15.8 4 ≈ 0.009 20589800 −603.58 143.663 0.2139 2001 Sheppard et al. Ananke
27 LIV S/2016 J 1 16.8 1 ≈ 0.00015 20595000 −603.81 139.836 0.1405 2016 Sheppard et al. Ananke
28 XL Mneme /ˈnm/ 16.3 2 ≈ 0.0015 20598300 −603.95 150.667 0.3250 2003 Gladman et al. Ananke
29 LXIV S/2017 J 3 16.5 2 ≈ 0.0015 20639300 −605.76 147.915 0.1477 2017 Sheppard et al. Ananke
30 XXIV Iocaste /əˈkæst/
15.4 5 ≈ 0.019 20644000 −605.96 147.837 0.2411 2000 Sheppard et al. Ananke
31 XXVII Praxidike /prækˈsɪdɪk/
14.9 7 ≈ 0.043 20718600 −609.25 147.012 0.3307 2000 Sheppard et al. Ananke
32 XII Ananke /əˈnæŋk/
11.7 29.1 ≈ 3.0 20740600 −610.22 148.721 0.2980 1951 Nicholson Ananke
33 (lost) S/2003 J 16 16.3 2 ≈ 0.0015 20744000
(20584500±161600)[51]
−610.36
(–603.40)[51]
150.769
(148.8±0.1)[51]
0.3184
(0.244±0.004)[51]
34 XLII Thelxinoe /θɛlkˈsɪn/ 16.3 2 ≈ 0.0015 21004500 −621.90 149.617 0.1146 2004 Sheppard et al. Ananke
35 XXXV Orthosie /ɔːrˈθz/
16.7 2 ≈ 0.0015 21075700 −625.07 146.466 0.3376 2001 Sheppard et al. Ananke
36 XLV Helike /ˈhɛlɪk/ 16.0 4 ≈ 0.009 21103900 −626.33 153.691 0.1455 2003 Sheppard et al. Ananke
37 LX Eupheme /jˈfm/ 16.6 2 ≈ 0.0015 21142900 −628.06 147.966 0.2532 2003 Sheppard et al. Ananke
38 LII S/2010 J 2 17.3 1 ≈ 0.00015 21195100 −630.39 148.251 0.2304 2010 Veillet Ananke
39 LXX S/2017 J 9 16.1 3 ≈ 0.0045 21430000 −640.90 152.661 0.2288 2017 Sheppard et al. Ananke
40 LXVII S/2017 J 6 16.4 2 ≈ 0.0015 22394700 −684.66 155.185 0.5569 2017 Sheppard et al. Pasiphae (fringe member)
41 LXXII S/2011 J 1 16.7 2 ≈ 0.0015 22401800 −684.98 163.341 0.2328 2011 Sheppard et al. Carme
42 XXXVII Kale /ˈkl/
16.4 2 ≈ 0.0015 22403600 −685.07 165.606 0.2090 2001 Sheppard et al. Carme
43 XXI Chaldene /kælˈdn/
16.0 4 ≈ 0.009 22538200 −691.25 165.078 0.2012 2000 Sheppard et al. Carme
44 XX Taygete /tˈɪɪt/
15.5 5 ≈ 0.016 22546200 −691.62 165.952 0.2488 2000 Sheppard et al. Carme
45 L Herse /ˈhɜːrs/ 16.5 2 ≈ 0.0015 22557900 −692.16 163.879 0.3574 2003 Gladman et al. Carme
46 XLIV Kallichore /kəˈlɪkər/ 16.4 2 ≈ 0.0015 22619900 −695.01 166.034 0.1988 2003 Sheppard et al. Carme
47 XXIII Kalyke /ˈkælɪk/
15.4 6.9 ≈ 0.04 22671900 −697.41 165.561 0.2006 2000 Sheppard et al. Carme
48 LXI S/2003 J 19 16.6 2 ≈ 0.0015 22696700 −698.56 166.657 0.2572 2003 Gladman et al. Carme
49 XXXVIII Pasithee /ˈpæsɪθ/
16.8 2 ≈ 0.0015 22712500 −699.28 165.988 0.3555 2001 Sheppard et al. Carme
50 (lost) S/2003 J 10 16.7 2 ≈ 0.0015 22731000
(22462600±670200)[52]
−700.13
(–687.83)[52]
163.813
(162.4±0.9)[52]
0.3438
(0.365±0.078)[52]
2003 Sheppard et al. Carme
51 (lost) S/2003 J 23
16.7 2 ≈ 0.0015 22740000
(23197700±421900)[53]
−700.54
(–721.87)[53]
148.850
(147.3±0.1)[53]
0.3931
(0.360±0.011)[53]
2004 Sheppard et al. Pasiphae
52 LVIII Philophrosyne /fɪləˈfrɒzɪn/ 16.7 2 ≈ 0.0015 22758800 −701.42 143.597 0.1945 2003 Sheppard et al. Pasiphae
53 XLVIII Cyllene /sɪˈln/ 16.3 2 ≈ 0.0015 22813100 −703.93 151.072 0.4763 2003 Sheppard et al. Pasiphae
54 LI S/2010 J 1 16.4 2 ≈ 0.0015 22892400 −707.61 165.686 0.2736 2010 Jacobson et al. Carme
55 XXVIII Autonoe /ɔːˈtɒn/
15.5 4 ≈ 0.009 22967700 −711.10 151.426 0.3010 2001 Sheppard et al. Pasiphae
56 XIX Megaclite /ˌmɛɡəˈklt/
15.0 5 ≈ 0.021 23097500 −717.14 146.934 0.3082 2000 Sheppard et al. Pasiphae
57 XXXII Eurydome /jʊəˈrɪdəm/
16.2 3 ≈ 0.0045 23148700 −719.53 152.552 0.4004 2001 Sheppard et al. Pasiphae
58 LXVI S/2017 J 5 16.5 2 ≈ 0.0015 23169400 −720.49 164.331 0.2842 2017 Sheppard et al. Carme
59 LXIX S/2017 J 8 17.0 1 ≈ 0.00015 23174400 −720.73 164.782 0.3118 2017 Sheppard et al. Carme
60 VIII Pasiphae /pəˈsɪf/
10.1 57.8 ≈ 30 23208900 −722.34 153.409 0.6110 1908 Melotte Pasiphae
61 XVII Callirrhoe /kəˈlɪr/
13.9 9.6 ≈ 0.087 23213100 −722.53 148.246 0.5206 1999 Spahr, Scotti Pasiphae
62 LVI S/2011 J 2 16.8 1 ≈ 0.00015 23213600 −722.55 149.182 0.3327 2011 Sheppard et al. Pasiphae
63 LXIII S/2017 J 2 16.4 2 ≈ 0.0015 23241000 −723.83 166.398 0.2360 2017 Sheppard et al. Carme
64 XXVI Isonoe /ˈsɒn/
16.0 4 ≈ 0.009 23322700 −727.65 164.459 0.2263 2000 Sheppard et al. Carme
65 XXXI Aitne /ˈtn/
16.0 3 ≈ 0.0045 23329000 −727.95 164.512 0.2664 2001 Sheppard et al. Carme
66 XXXIX Hegemone /hɪˈɛmən/ 15.9 3 ≈ 0.0045 23441900 −733.24 157.803 0.5148 2003 Sheppard et al. Pasiphae
67 XXXVI Sponde /ˈspɒnd/
16.7 2 ≈ 0.0015 23477000 −734.89 151.135 0.3137 2001 Sheppard et al. Pasiphae
68 XLVII Eukelade /jˈkɛləd/ 15.9 4 ≈ 0.009 23480100 −735.03 163.790 0.1678 2003 Sheppard et al. Carme
69 (lost) S/2003 J 4 16.6 2 ≈ 0.0015 23571000
(22766700±1780200)[54]
−739.29
(–701.85)[54]
147.176
(143.2±1.3)[54]
0.3003
(0.270±0.030)[54]
2003 Sheppard et al. Pasiphae
70 XXV Erinome (unknown)
16.0 3 ≈ 0.0045 23575700 −739.53 166.569 0.3388 2000 Sheppard et al. Carme
71 XLIII Arche /ˈɑːrk/
16.2 3 ≈ 0.0045 23649500 −743.00 167.064 0.2869 2002 Sheppard et al. Carme
72 LVII Eirene /ˈrn/ 15.8 4 ≈ 0.009 23668100 −743.88 163.142 0.2216 2003 Sheppard et al. Carme
73 (lost) S/2003 J 9 16.9 1 ≈ 0.00015 23858000
(23183400±213900)[55]
−752.84
(–721.21)[55]
164.980
(164.8±0.4)[55]
0.2762
(0.233±0.023)[55]
2003 Sheppard et al. Carme
74 XI Carme /ˈkɑːrm/
10.6 46.7 ≈ 13 23926500 −756.09 165.637 0.2241 1938 Nicholson Carme
75 XLI Aoede /ˈd/ 15.6 4 ≈ 0.009 24011900 −760.14 150.343 0.4901 2003 Sheppard et al. Pasiphae
76 XLIX Kore /ˈkɔːr/ 16.6 2 ≈ 0.0015 24345100 −776.02 137.372 0.1951 2003 Sheppard et al. Pasiphae
77 IX Sinope /sɪˈnp/
11.1 35 ≈ 7.5 24371600 −777.29 158.638 0.3367 1914 Nicholson Pasiphae
78 LIX S/2017 J 1 16.6 2 ≈ 0.0015 24441400 −780.63 148.222 0.3106 2017 Sheppard et al. Pasiphae
79 (lost) S/2003 J 2 16.6 2 ≈ 0.0015 30291000
(27734700±10756100)[56]
−1077.02
(–943.69)[56]
153.521
(151.3±2.5)[56]
0.1882
(0.120±0.002)[56]
2003 Sheppard et al. Pasiphae? (unconfirmed)

## Exploration

The orbit and motion of the Galilean moons around Jupiter, as captured by JunoCam aboard the Juno spacecraft.

The first spacecraft to visit Jupiter were Pioneer 10 in 1973, and Pioneer 11 a year later, taking low-resolution images of the four Galilean moons and returning data on their atmospheres and radiation belts.[57] The Voyager 1 and Voyager 2 probes visited Jupiter in 1979, discovering the volcanic activity on Io and the presence of water ice on the surface of Europa. The Cassini probe to Saturn flew by Jupiter in 2000 and collected data on interactions of the Galilean moons with Jupiter's extended atmosphere. The New Horizons spacecraft flew by Jupiter in 2007 and made improved measurements of its satellites' orbital parameters.

The Galileo spacecraft was the first to enter orbit around Jupiter, arriving in 1995 and studying it until 2003. During this period, Galileo gathered a large amount of information about the Jovian system, making close approaches to all of the Galilean moons and finding evidence for thin atmospheres on three of them, as well as the possibility of liquid water beneath the surfaces of Europa, Ganymede, and Callisto. It also discovered a magnetic field around Ganymede.

In 2016, the Juno spacecraft imaged the Galilean moons from above their orbital plane as it approached Jupiter orbit insertion, creating a time-lapse movie of their motion.[58]

## Notes

1. ^ For comparison, the area of a sphere with diameter 250 km is about the area of Senegal and comparable to the area of Belarus, Syria and Uruguay. The area of a sphere with diameter 5 km is about the area of Guernsey and somewhat more than the area of San Marino. (But note that these smaller moons are not spherical.)
2. ^ Jupiter Mass of 1.8986 × 1027 kg / Mass of Galilean moons 3.93 × 1023 kg = 4,828
3. ^ Order refers to the position among other moons with respect to their average distance from Jupiter.
4. ^ Label refers to the Roman numeral attributed to each moon in order of their naming.
5. ^ Diameters with multiple entries such as "60 × 40 × 34" reflect that the body is not a perfect spheroid and that each of its dimensions has been measured well enough.
6. ^ Periods with negative values are retrograde.
7. ^ "?" refers to group assignments that are not considered sure yet.

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