Astronomy Final Study Guide
Jupter and Saturn’s Satellites
Jupiter’s Satellites= Galiliean Satellites
Io, Europa, Ganymede and Callisto
Synchronous rotation for all 4- Rotates once on it’s axis for each orbit around Jupiter
1:2:4- Orbital ratios of Io, Europa and Ganymede. Gravitational rhythms maintain this ratio
Transit- a satellite passes between us and Jupiter.
Occultation- satellites pass completely behind Jupiter.
Ganymede and Callisto are the largest. Both have low average densities. They are composed of
equal parts of rock and water ice.
Io and Europa are about as dense as the moon, which means they’re primarily rocky. Only Io
shows no traces of water in it.
Jupiter and it’s satellites formed like a miniature solar system. Jupiter emitted lots of heat while it
was forming, so it’s closest satellites Io and Europa couldn’t retain water, where as Ganymede
and Callisto could.
Io is covered with colorful sulfur compounds ejected from active volcanoes. Tidal heating from
it’s orbit causes it’s internal heat. Most volcanically active world in the solar system.
Rather than volcanoes on Io, there are actually geysers. Sulfur dioxide is heated up in the
interior and then shot out through the geysers. When the sulfur dioxide is released into the
atmosphere it cools down and then snows back down to the surface. There are also lava flows
that are more dramatic flows than on Earth.
The lava on Io has magnesium in it, which gives it a higher melting temperature, which explains
why the lava doesn’t evaporate instantly.
Io has mountains because the lava is tilted during rotation, so the lava piles up.
When charged particles hit Io they knock ions off of it’s surface. This ejected material forms the
Io torus, which is a huge doughnut shaped ring of ionized gas or plasma that sits in Io’s orbit. As