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Planetary Systems

Jovian Planets - Jupiter, Saturn, Uranus, Neptune

Outer Planets Gushing Moons As shown in Figure 07-11a, the giant outer planets consist mostly of hydrogen and helium gas and liquid, which surrounds a core of iron and rock and possibly a smaller amount of methane, carbondioxide and water ices. Jupiter is the largest planet, closely followed by Saturn. Uranus and Neptune are in comparison much smaller, although still significantly larger than any of the terrestrial planets. Jupiter is a "failed star" - it would have become a star igniting nuclear fusion at its core if its mass is about 80 times higher (the lowest mass limit for a star to form is about 0.05 MSun).

Figure 07-11a The Jovian Planets
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Figure 07-11b Gushing Moons
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Two of the Jovian Planets each owns a moon gushing out water from ocean under the icy surface. They are candidates for future missions to find life in alien seas (Figure 07-11b).

Many of the satellites in Jovian planets will be the landing sites for further exploration of the outer Solar system. Unlike the Jovian planets with surface in liquid form and thick cloud layers, some of the satellites offer a solid ground to stay, and they are more likely to provide clues about life in outer space.

Over the last 45 years, NASA has launched eight spacecrafts to study the planets in the outer solar system. Figure 07-19c presents the year of rendezvous for the various missions with links to their home pages, which contain a lot of information the textbooks are not able to keep up.
NASA Missions

Figure 07-19c NASA Outer Solar System
Missions [view large image]

Spacecraft Home
Page [click icon]

The Europa Clipper is the only outer planet mission planned (in 2020s) by NASA since the launched of Juno on 2011.

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