Line #113 UsefulNotes/TheMoonsOfJupiter


1	[[quoteright:250:https://static.tvtropes.org/pmwiki/pub/images/250px-Jupiter_family_4554.jpg]]
2
3	->''"All of these worlds are yours, except Europa. Attempt no landings there. (Use them together. Use them in peace.)"''
4	-->-- ''[[Literature/TheSpaceOdysseySeries 2010: Odyssey Two]]'' (The addition comes from [[Film/TwoThousandTenTheYearWeMakeContact the film version]] of the novel.)
5
6	At last count, UsefulNotes/{{Jupiter}} had ''95'' moons, of which 52 are named. Many of these have only been found in the last decade. They are all named after the lovers and descendants of Jupiter/Zeus (''[[DoubleStandardRapeDivineOnMortal God of Horndogs]]!''), so you can tell he really got around. (The names of the lovers and descendants are generally the same or negligibly different between Greek and Latin, so there's not much of an issue, but in case of discrepancy both names tend to get used.)
7
8	The first four to be found (Io, Europa, Ganymede and Callisto) were discovered by Galileo himself, and thus are called the Galilean Moons. These are the only four Jovian moons massive enough to become spherical under their own gravity. They dealt a significant blow to the notion that the Earth was the center of the universe, although [[CommonKnowledge contrary to popular belief]] they did not disprove the idea altogether; the existence Jupiter's moons did not have any bearing on the question of whether Jupiter itself orbited the Earth. Galileo [[YesMan wanted to name them after his patrons]], the Medicis, but later generations of astronomers thought otherwise. One night after Galileo discovered them, a German by the name of Simon Marius — who'd independently gotten the idea of pointing a telescope at the heavens — also saw the same four moons, and named them after four of {{UsefulNotes/Jupiter}}'s lovers from Myth/ClassicalMythology; it's these names that are still in use today.
9
10	The discovery of the four Galilean moons was a major blow to the geocentric model of the universe. Until Isaac Newton defined his Laws of Gravity, it was widely held that Earth could not revolve around the Sun because the Moon would be left behind. Once it was observed that Jupiter was clearly dragging four objects along its orbit, it raised the question of why Earth couldn't do the same with the Moon. (That being said, it wasn't definitive proof; there was also strong evidence that while the planets revolved around the Sun, the Sun and Moon might revolve around the Earth. Solid proof of the Sun-centered Solar System would not come until the 19th century, when astronomers measured parallax in a star that showed the stars to be super-far away. By that point, most astronomers had accepted heliocentrism, but they were basing it on a sense that that solution, which was more elegant, was more likely true, rather than solid evidence.) The Galilean moons are much larger than all the others, similar in size to Earth's moon.
11
12	!!The innermost moons (Metis, Adrastea, Amalthea, Thebe)
13	[[quoteright:220:https://static.tvtropes.org/pmwiki/pub/images/220px-Amalthea_Voyager-1_8903.gif]]
14	[[caption-width-right:220:Amalthea]]
15
16	Four irregular-shaped moons, being pretty small and not large enough to form into spheres. Due to tidal forces, the first two will eventually drop into the planet or break up into ring particles. The largest, Amalthea, was discovered in 1892 and is very, very red. The radiation levels this close to {{UsefulNotes/Jupiter}} ''will'' kill you faster than you can say "non-functional DNA".
17
18	Amalthea didn't get its name until the mid-20th century; before then it was simply known as "Jupiter V" (as in the Roman numeral 5). Creator/ArthurCClarke wrote a short story by this name, which posited it was an alien starship (yes, the entire moon).
19
20	!!Io! It's Blazin'!
21	[[quoteright:200:https://static.tvtropes.org/pmwiki/pub/images/io-globe-bg_8949.jpg]]
22	[floatboxright:
23	'''Profile'''
24	* Diameter: 3,643 km
25	* Mass: 0.015 of Earth
26	* Density: 3.53 g/cm3
27	* Surface Gravity: 0.18 g
28	* Semi-major Axis: 421,700 km from Jupiter
29	* Orbital Period: 42 Hours (1:1 Laplace Resonance with Europa and Ganymede)
30	* Rotational Period: 42 Hours (Tidally Locked)
31	* Axial Tilt: 0.05° to Jupiter's Equator (3.13°), 2.21° to Ecliptic Plane
32	* Average Surface Temperature: -163° C
33	* Notable Features: Loki Patera
34	* Discovered: 1610 by UsefulNotes/GalileoGalilei
35	]
36
37	[[{{Pun}} A real hot spot in the Solar System, in a lot more ways than one]].
38
39	About 3640 km in diameter, Io is one of the Galilean moons. Slightly larger than our moon, its relatively close orbit to Jupiter means that it is the largest moon as seen from the surface of its parent planet in the solar system. Its (relatively) high density also makes it the moon with the highest gravitational pull in the solar system, again slightly ahead of our own moon.
40
41	Because of its close proximity to its host and the pull from its brothers, Io suffers from huge tidal forces 20,000 times stronger than the ones our moon experiences, [[LethalLavaLand resulting in constant volcanic eruptions jutting out hundreds of kilometers into space]]. This means the colourful surface, resembling a pizza due to massive deposits of sulfur, is constantly changing. Most of the material in {{UsefulNotes/Jupiter}}'s magnetosphere comes from Io's volcanoes, including the radiation belts and a gas and plasma ring near Io's orbit; as Io's surface gravity is only 18.3% as strong as Earth's, its volcanic gases can easily reach escape velocity. The radiation levels (3600 rem/day) this close to Jupiter as a result will kill you, but you'll have a few hours to savor the unfairness of it all before your nervous system collapses.
42
43	Its surface features are named after gods of fire, thunder and lightning, the Sun, or blacksmithing (Ra Patera, the volcanoes Pele and Surt, etc.) Given its extreme geological activity, it's questionable how long any of these surface features will last. Based on observations via the Voyager and Galileo probes, Io only needs a mere ''sixteen years'' to replace all of its surface features.
44
45	Io was the setting for the movie ''Film/{{Outland}}'', and is also the homeworld of Arnold Judas Rimmer, from ''Series/RedDwarf''. The radiation levels may explain much about the Rimmer family, especially Arnold. Also the last world [[VideoGame/Destiny2 touched by the Traveler]]. It also hosts a series of racetracks in ''VideoGame/{{Redout}} II''. In the EdutainmentGame ''VideoGame/TheMagicSchoolBus Explores the Solar System'', Io is where you make your landing when you travel to Jupiter. Inexplicably, ''Series/Babylon5'' has a major Earth Alliance space station, including Sol system's primary [[PortalNetwork jumpgate]], orbiting Io. Why this is so given the extreme radiation, debris hazards, steepness of Jupiter's gravity well, and instability of orbits around something close to a much larger celestial body is not explained
46
47	Other than Galileo making [[TheLastDance a suicide run for its final mission.]][[note]]And even then the many mechanical problems experienced by Galileo meant that a lot of data was never acquired.[[/note]] Io's close proximity to Jupiter and the sheer amount of radiation experienced at that distance means that the moon hasn't been studied very closely compared to the other Galilean ones. And the below mentioned JUICE will for the most part skip it. A couple dedicated missions are proposed though, such as the NASA [[https://en.wikipedia.org/wiki/Io_Volcano_Observer Io Volcano Observer]] (IVO) and the CNSA [[https://en.wikipedia.org/wiki/Tianwen-4 Tianwen-4]]. Booth of which may launch in around 2029 if accepted.
48
49
50	!!Attempt No Landings on Europa
51	[[quoteright:200:https://static.tvtropes.org/pmwiki/pub/images/Europa2_501.jpg]]
52	[floatboxright:
53	'''Profile'''
54	* Diameter: 3,121 km
55	* Mass: 0.008 of Earth
56	* Density: 3.01 g/cm3
57	* Surface Gravity: 0.13 g
58	* Semi-major Axis: 670,900 km from Jupiter
59	* Orbital Period: 3 Days (2:1 Laplace Resonance with Io and Ganymede)
60	* Rotational Period: 3 Days (Tidally Locked)
61	* Axial Tilt: 0.47° to Jupiter's Equator (3.13°), 1.79° to Ecliptic Plane
62	* Average Surface Temperature: -171° C
63	* Notable Features: Argadnel Regio, Conamara Chaos, Possible Sub-surface Ocean
64	* Discovered: 1610 by UsefulNotes/GalileoGalilei
65	]
66
67	Just smaller than {{UsefulNotes/the Moon}}, Europa is covered by a cracked, frozen ocean (smoother than a billiard ball would be if it was the same size) and has a tenuous atmosphere (on Earth it would be considered a pretty decent vacuum). It may support simple life under the surface. Here the radiation levels (540 rem/day) are less, so you'll have [[http://en.wikipedia.org/wiki/Walking_ghost_phase up to a week or so to get your affairs together]]. [[Film/TwoThousandTenTheYearWeMakeContact Attempt no landings here]]. However, the ocean under the ice is considered a good place to colonize: the thick ice crust protects from radiation; the water provides, well, water, and a ready if potentially expensive source of oxygen; and the same forces keeping the ocean liquid substantially cuts down your heating bill.
68
69	Its surface features are named after places and myths of the Celtic mythos (Tara Regio, the crater Pwyll, etc.). Surface gravity is 13.4% of Earth's.
70
71	As shown in the page quote, Europa played a prominent role in ''[[Film/TwoThousandTenTheYearWeMakeContact 2010: The Year We Make Contact]]''. The moviemakers making it ''2001''[='=]s target instead of [[UsefulNotes/TheMoonsOfSaturn Saturn's Iapetus]] was VindicatedByHistory; its subsurface ocean is today considered the most likely candidate to host extraterrestrial life in this Solar System, even more so than UsefulNotes/{{Mars}},[[note]]To put it in perspective, it's taken as read that if Mars had life, it's going to be microbial, and already ''[[UsefulNotes/{{NASA}} Curiosity]]'''s analysis of the Martian soil makes it extremely unlikely that even that is there. On the other hand, the Europan sea might very well bear more complex life (sure, it'd probably be anoxic, but there's nothing suggesting that anoxic biochemistries couldn't make complex forms) — and we have nothing that suggests it might be otherwise.[[/note]] although since about 2015, [[UsefulNotes/TheMoonsOfSaturn Enceladus]] has given Europa a run for its money in that department.
72
73	Due to its interesting status in the solar system, Europa has been the subject of many proposed probe launches to study or even drill into its surface. Most famous was probably the joint ESA/NASA [[https://en.wikipedia.org/wiki/Europa_Jupiter_System_Mission_%E2%80%93_Laplace Europa Jupiter System Mission – Laplace]] (EJSM/Laplace) that unfortunately never got out of the planning stage. Or at least not in its original context, as both NASA and ESA have planned probes to jointly study Europa: [[https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Explorer Jupiter Icy Moons Explorer]] and the [[https://en.wikipedia.org/wiki/Europa_Clipper Europa Clipper]]. Both of which will make several flybys at around 2029 and 2026-31 respectively depending on launch window.
74
75	* ''Film/EuropaReport'' is a FoundFootage film examining what happened to an expedition to Europa.
76	* ''Series/StarTrekPicard'''s second season revolves around a crewed NASA mission to Europa, launched in 2024.
77	* Attempts at colonizing Europa were made in the backstory for ''VideoGame/{{Redout}}'', though they were eventually abandoned and used as racetracks instead.
78
79
80	!!Big Brother Ganymede
81	[[quoteright:250:https://static.tvtropes.org/pmwiki/pub/images/250px-Noaa_ganymede_4473.jpg]]
82	[floatboxright:
83	'''Profile'''
84	* Diameter: 5,268 km
85	* Mass: 0.025 of Earth
86	* Density: 1.936 g/cm3
87	* Surface Gravity: 0.15 g
88	* Semi-major Axis: 1,070,400 km from Jupiter
89	* Orbital Period: 7 Days (4:1 Laplace Resonance with Europa and Io)
90	* Rotational Period: 7 Days (Tidally Locked)
91	* Axial Tilt: 0.20° to Jupiter's Equator (3.13°), 2.21° to Ecliptic Plane
92	* Average Surface Temperature: -163° C
93	* Notable Features: Galileo Regio, Osiris Crater, Possible Sub-surface Ocean
94	* Discovered: 1610 by UsefulNotes/GalileoGalilei
95	]
96
97	The largest moon in UsefulNotes/{{the Solar System}}. Larger than {{UsefulNotes/Mercury}}, it could count as a planet on its own if it weren't already attached to one. Its surface shows evidence of past geological activity. A popular sci-fi (and one-off ''Series/PowerRangersInSpace'') setting, even if it is really just a bigger version of {{UsefulNotes/the Moon}}, in other words, deader than tanktops. In ''Series/PowerRangersInSpace'', it is shown that Zordon hid the components of the Mega Voyager Zord here in case of emergencies. The radiation here (8 rem/day) won't kill you directly, but you might want to invest in a surrogate gamete donor (those eggs and sperm cells spoil easy!) or an MRI machine (so you can get a cancer scan every six months or so).
98
99	Despite being larger than Mercury, Ganymede isn't as dense. It's less than half of Mercury's mass[[labelnote:*]]45%, specifically[[/labelnote]], and its surface gravity is only 14.6% of Earth's. (Mercury, by contrast, has 38% of Earth's surface gravity, the same as the surface gravity on {{UsefulNotes/Mars}}.) As the Moon has approximately 16.6% of Earth's gravity, you could expect to be able to pull off similar feats of acrobatics if you happened to find yourself here.
100
101	It is the only moon known to produce its own magnetic field. The second strongest of any rocky body in fact and roughly 3% of that of Earth's; which sounds about right considering it has 2.5% of earth's mass. The origin of the field and why similar moons don't have one we have no idea, but it might suggest the presence of a liquid iron core similar to that of earth's that's kept in such a state by the same tidal forces that keeps Europa's ocean from freezing. The moon would probably also have some really spectacular auroras as the field interacts with the Jovian plasma.
102
103	Its surface features are named after locations and [[Myth/EgyptianMythology myths]] of AncientEgypt and Mesopotamia (Tiamat Sulcus, Memphis Facula, etc.). Many of these features are tectonic, possibly formed by tidal heating or by expansion of the moon. Most features, tectonic or crater, appear to have formed several billion years ago over roughly the same time.
104
105	It was discovered March 2015 that Ganymede has a subsurface ocean like Europa. This was found out by measuring Ganymede's aurora; normally, an aurora is very wobbly, but Ganymede's aurora is stable, which is only possible in the presence of a large quantity of salt water.
106
107	Ganymede will also be the main target of ESA's [[https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Explorer Jupiter Icy Moons Explorer]] (JUICE). Who after doing several flybys of the three outer moons will become the first probe to enter orbit around a natural satellite that isn't ours.
108
109	* ''Literature/TheGanymedeTakeover'' by Creator/PhilipKDick and Ray Nelson is about the occupation of Earth by alien invaders from Ganymede.
110
111	!!Craterface Callisto
112	[[quoteright:250:https://static.tvtropes.org/pmwiki/pub/images/250px-Callisto_7246.jpg]]
113	[floatboxright:
114	'''Profile'''
115	* Diameter: 4,820 km
116	* Mass: 0.018 of Earth
117	* Density: 1.83 g/cm3
118	* Surface Gravity: 0.13 g
119	* Semi-major Axis: 1,882,700 km from Jupiter
120	* Orbital Period: 16 Days
121	* Rotational Period: 16 Days (Tidally Locked)
122	* Axial Tilt: 0.19° to Jupiter's Equator (3.13°), 2.02° to Ecliptic Plane
123	* Average Surface Temperature: -139° C
124	* Notable Features: Valhalla Basin
125	* Discovered: 1610 by UsefulNotes/GalileoGalilei
126	]
127
128	Almost as big as {{UsefulNotes/Mercury}} and the third biggest moon in the Solar System, this dead world is outside the main radiation belts of {{UsefulNotes/Jupiter}} and is the outermost Galilean moon. At larger scales, it's covered by craters on top of other craters. At smaller scales, the surface shows more variety, with plains and knobs, probably formed by the erosion of yet more craters. The general calmness of the place (0.01 rem/day average) makes it a good location to colonize, but most writers tend to ignore it. In fact, it has ''seven times less'' radiation than even our own Earth.
129
130	Callisto is the only Galilean moon not part of an orbital resonance with the others.[[note]]Its expected to join up with the rest though in around 1.5 billion years or so. Creating an 8:1 Laplace resonance[[/note]] Due to the resulting lack of tidal forces from the other three Galilean moons, Callisto's surface has remained largely unchanged since it was bombarded in the early days of the Solar System, making it a valuable source of information about the conditions of that time. This lack of tidal heating also makes Callisto the largest non-differentiated body in the Solar System.
131
132	Its surface features are named after elements of northern ([[Myth/NorseMythology Norse]], [[Myth/CelticMythology Celtic]], Inuit, Uralic, etc.) myths (Valhalla Basin, the crater Bran, etc.). Surface gravity is 12.6% of Earth's.
133
134	* In ''Literature/AlienInASmallTown,'' humanity has permitted the [[SiliconBasedLife silicon-based]] Jan to colonize (and begin terraforming - or rather, Janniforming) Callisto, in exchange for their help establishing humanity in the local interstellar community.
135
136	Like with Ganymede and Europa, The [[https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Explorer Jupiter Icy Moons Explorer]] (JUICE) will visit Callisto at around 2029.
137
138	!!The Rest of the Mess (Themisto, Leda, Himalia, Lysithea, etc.)
139
140	Also known as irregular satellites, they're believed to be captured asteroids and are probably not permanently attached to {{UsefulNotes/Jupiter}}. They're grouped into 4 separate families (except for three ungrouped outliers) based on their orbits, and they all stay far away from the big guys in the middle.
141

Context UsefulNotes / TheMoonsOfJupiter