Properties of the Jovian Planets
- As a group, the Jovian planets (Jupiter, Saturn, Uranus, and Neptune) can best be described as large gasballs - or better yet, spinning drops of liquid.
- More specifically, Jupiter and Saturn are composed mostly of Hydrogen and some Helium - both of which are gasses under Earthly conditions, but are ultradense liquids deep inside Jupiter and Saturn.
- Jupiter and Saturn are composed of the same mix of elements
as the Sun -- mainly hydrogen and helium.
- The trace atmospheric constituents are
water, methane, and ammonia.
- They probably have tiny rocky/slushy cores
that represent the "seed" around which the gas mantle
accumulated during the formation of the Solar System.
- Under extreme pressure the gasses in these planets
behave more like a liquid (and even conduct electricity like
- Uranus and Neptune are not nearly as massive as Jupiter and Saturn.
- Although they may have thick gas mantles,
their rocky/slushy cores may make up half the radius
of the planet or more.
- Astronomers often refer to this pair as ``ice giants."
- These planets are thought to have formed more slowly
and thus had less opportunity to gather gas
gravitationally from the "solar nebula."
- Since they are largely atmosphere, the clouds of these planets represent their apparent surface.
- The highest whitest clouds of Jupiter and Saturn are made of ammonia ice crystals while those of Uranus and Neptune are methane ice.
- At Jupiter and Saturn it is warm enough for methane to be gaseous. At Uranus and Neptune temperatures are low enough in the upper atmosphere to form methane ice.
- Lower cloud decks of Jupiter and Saturn are ammonium hydrosulfide and ordinary water clouds.
- Unknown chemical compounds provide the cloud's colors.
- Due to the rapid rotation and large size of these
worlds the atmospheric circulation gets organized into
a number of "belts'' and "zones.''
- All four of these planets have large systems of satellites
- Jupiter and Saturn each have 63 and 33 known ``moons" respectively with the number growing every day.
- Most of the recent discoveries are more like large rocks/asteroids rather than significant satellites.
- The four "Galilean" satellites of Jupiter are all of
- So are Titan (Saturn) and Triton (Neptune), both of which
- All four of these planets have rings. Saturn's are the
Revised April 18, 2005