Deep Space Probe Exploration of the Outer Planets
The outer planets, also known as the Jovian planets, consist of Jupiter, Saturn, Uranus and Neptune. The first probe to explore Jupiter was the Pioneer 10 spacecraft. The Pioneer 11 spacecraft sent back information on Jupiter and Saturn. But it was the Voyager 2 spacecraft launched by the National Aeronautics and Space Administration (NASA) in 1977 that explored all the outer planets in great detail for the first time. We will look at the outer planets and the data Voyager 2 gathered on them:
1. Jupiter: Jupiter is the largest planet in the Solar System. The gas giant has a mass two and half times that of all the planets combined. The Jupiter system is composed of 63 known moons. Jupiter is primarily composed of hydrogen and helium. Trace amounts in the atmosphere of water vapor, methane, ammonia, hydrogensulfide, neon, oxygen and sulfur also exist.
The internal structure of Jupiter is thought to be of a dense core composed of a variety of elements, surrounded by a layer of liquid metallic hydrogen with an outer layer of molecular hydrogen. As one moves towards the core, the temperature and pressure steadily increase. The atmosphere on Jupiter is extremely thick. Clouds comprised of ammonia crystals and ammonium hydrosulfide are arranged into bands. The bands occur at different altitudes. Circulation patterns similar to Earth cause a great amount of turbulence and massive storms. The Great Red Spot is one such anti-cyclonic storm on Jupiter that is larger than Earth.
The Voyager 2 spacecraft began its survey of the planet in 1979. Many important discoveries were revealed for the first time by the spacecraft. These included the satellites of Jupiter, radiation belts and its planetary rings. The discovery of volcanic activity on Io, one of Jupiter's moons, and the discovery of the Great Red Spot also came as a big surprise.
2. Saturn: Saturn is the second largest planet in the Solar System. Saturn is also a gas giant similar to Jupiter. There are 62 known moons in the Saturnine system. The interior of Saturn is comprised of a core of variety of elements, surrounded by metallic hydrogen, followed by a layer of liquid hydrogen and liquid helium and an outer gaseous layer. The atmosphere of Saturn is comprised mostly of hydrogen and some helium. Trace amounts of ammonia and methane have also been detected.
Saturn's cloud patterns are very similar to that of Jupiter. Saturn is probably best known for its rings which are comprised mostly of water ice and some amorphous carbon. Voyager 2 came in contact with Saturn in 1980. The probe's cameras detected complex structures in the rings of Saturn; particles in the rings ranging from dust grains to the size of automobiles. Instruments aboard Voyager 2 also studied the atmosphere of Saturn and determined the planet's surface temperature at the deepest levels to be -203 degrees Celsius.