1 The Jovian Planets

2 Topics l Introduction l Images l General Properties l General Structure l Jupiter l Summary

3 p.134

4 Table, p.136

5 Fig. 7-3b, p.136

6 Saturn

7 Saturn’s Ring System

8 Uranus

9 Fig 7-27, p.150

10 Neptune

11 General Properties – I l Massive and cold l Jovian planets are large and cool enough to retain their primary atmospheres of H and He l Powerful gravitational forces Roche ( ) Limit l Strong enough to tear planets apart if they approached too closely – that is, closer than the Roche ( ) Limit of just over one planetary diameter. l This could be the origin of some ring systems.

12 General Properties – II l Great internal pressure liquid metallic hydrogen l Enough to compress hydrogen into a form called liquid metallic hydrogen. l Powerful magnetic fields l Caused by the rapid rotation of this metallic liquid. The strong magnetic fields trap charged particles from the Sun. l Powerful cyclonic activity

13 General Structure l Clouds l Ammonia and water ice (Jupiter and Saturn) l Methane ice (Uranus and Neptune) l Atmosphere l Hydrogen and helium l Ocean l Liquid metallic hydrogen l Core l Rock

14 Jupiter

15 Jupiter – I l Radius l 71,490 km (equatorial); l 66,850 km (polar). l Mass l 318 times that of the Earth. l Rotation l About 10 hours. l Average distance from Sun l 778,330,000 Km (5.2 AU).

16 Jupiter – II l Internal pressure and heating l The pressure on the ocean is predicted to be about 4 million times that on Earth’s ocean. l The core is under enormous pressure and its temperature may be as high as 20,000 K. l Jupiter radiates more energy than it absorbs from the Sun.

17 Fig 7-6, p.139

18 Jupiter: Moons and Ring System l At least 52 moons. l Galilean Satellites l Io – Highly volcanic; few craters. Io l Europa – Smooth, lined, few craters. Europa l Ganymede – Largest satellite in the Solar System; rock and ice l Callisto – outermost; rock and ice. l Discovered in 1610 by Galileo and Simon Marius ( ). l Ring system discovered by Voyager 1 in 1979.

19 Fig 7-9, p.141

20 Jupiter and Io

21 Io

22 Europa

23 Fig 7-12, p.142

24 Galileo Probe – I l The Galileo Space Probe was launched on October 18, 1989 from Space Shuttle Atlantis.Galileo Space Probe l On December 7th, 1995 a 339-kilogram probe was released from the Galileo Orbiter. l During the first 2 minutes of deceleration the temperature near the probe reached about 12,000 K, which is twice the temperature of the Sun's surface. The deceleration forces were 230 times stronger than the acceleration due to gravity on the Earth.

25 Galileo Probe – II l The probe's radio transmission lasted for 57 minutes and the probe reached a depth of 600 km (373 miles) into the atmosphere. l We presume the probe was destroyed by the extreme environmental conditions of Jupiter's atmosphere. l The pressure at that depth is the same as the pressure (22 atmospheres) at a depth of 230 meters below the surface of Earth's ocean.

26 Galileo Probe – III l Jupiter's atmosphere was found to be drier and windier than expected. There was also less helium than expected. One explanation is that the helium, being denser than hydrogen, has sunk towards the core. l Also, there was a much lower density of complex organic molecules than expected. It is therefore extremely unlikely that any kind of life-form exists in the Jovian atmosphere.

27 Cassini-Huygens Mission l Launched l Kennedy Space Center on Oct. 15, 1997 l Reach Saturn in July l Mission l Cassini orbiter will orbit Saturn and its moons for four years l Huygens probe will land on Titan. l International collaboration l NASA l European Space Agency l Italian Space agency l Web-site:

28 Summary l Owing to their mass, the Jovian planets were able to retain much of their primary atmospheres. l Jupiter and Saturn, the “gas giants”, have a composition similar to that of the Sun, whereas Uranus and Neptune, the “ice giants”, are quite different. l The extreme pressures at the base of the atmospheres of Jupiter and Saturn has yielded planet-wide oceans of liquid metallic hydrogen. l The interiors of the giant planets are hot and dense. l All Jovian planets have ring systems and many moons.