Moons

The four largest moons are called Io, Europe, Ganymed and Callisto and were already discovered 1610 by Galileo Galilei. Their distances from Jupiter amount to 422'000 km, 671'000 km, 1'070'000 km and 1'883'000 km, their periods of revolution 1,8 d, 3,6 d, 7,2 d, 16,7 d and their diameters 3'632 km, 3'126 km, 5'276 km and 4'820 km. The surfaces are quite different: IO shows a strong volcanism: The Voyagerprobes photographed several outbreaks. Europe however is covered by a thick shell of ice which is full of cracks. Ganymed and Callisto have many craters. The average density of the moons augments with decreasing distance from the planet: Io has a density of 3.5 g/cm^3 Callisto only one of 1.8 g/cm^3. The other 12 moons can not be observed with normal telescopes. Here is a table with some characteristics of all moons:

Moon	Year of discoverey	Average distance form Jupiter (km)	Time of revolution around Jupiter (days)	diameter (km)
Metis	1980	127'600	0.95	~ 40
Adrasteia	1979	~128'400	0.97	~35
Amalthea	1892	181'300	0.498	155*720
Thebe	1980	225'000	0.678	~75
Io	1610	421'600	1.769	3'632
Europa	1610	670'900	3.551	3'126
Ganymed	1610	1'070'000	7.155	5'276
Callisto	1610	1'883'000	16.69	4'820
Leda	1974	11'100'000	238.7	8
Himalia	1904	11'470'000	250.6	170
Lysithea	1938	11'710'000	259.2	19
Elara	1905	11'743'000	259.7	80
Ananke	1951	20'700'000	631	17
Carme	1938	22'350'000	692	24
Pasiphae	1908	23'300'000	744	27
Sinope	1914	23'7000	758	21


The Jupitermoon Callisto © NASA	The Jupitermoon Amalthea © NASA