The Gas Giants

1. The Gas Giants

2. Jupiter

3. Exploration of Jupiter • Four large moons of Jupiter discovered by Galileo (and now called the Galilean satellites) • Great Red Spot likely seen by Hooke (1664) or Cassini (1665) • 1st flybys – Pioneer 10 in 12/73 and Pioneer 11 in 12/74 • Better flybys – Voyager 1 in 3/79 and Voyager 2 in 7/79 (Voyager 1 discovered Jupiter’s ring) • Galileo probe – arrived 1995, very successful and long lasting mission until 2003

4. Jupiter from the Shadow Side

5. Jupiter’s Atmosphere • Solar input: 5x farther than Earth, so Sun only 1/5 as large in sky, sunlight only 1/25 as bright • Composition: (by mass) 79% H2, 19% He, so the ratio H/He ~ 4 trace amounts of: H2O water CH4 methane NH4 ammonia • Appearance: complex gas dynamics alternating dark belts and bright zones

6. Spectrum of Jupiter • Right shows how Jupiter glows at different colors: • Red indicates sunlight reaching Jupiter • Blue indicates reflected sunlight from Jupiter’s atmosphere. • Green shows Jupiter’s IR emission. • Spiky features are from atmospheric molecules.

8. Jupiter's chemical composition is closest to that of a) Earth b) the Sun c) Mars d) the Moon e) Venus Share Question

9. Jupiter’s Atmospheric Structure

10. Atmospheric Features • IR measurements: • Dark belts - deep, warmer levels • Bright zones - high upwelling clouds in the cold upper atmosphere • Winds: • Wind speeds in excess of 350 kph • E. and W. jet streams • Misc.: • Lightning • Aurorae at poles

11. Appearance of Jupiter at Long Wavelengths Jupiter at IR Jupiter at Radio

12. Jupiter’s Dynamic Atmosphere and UV Aurorae

13. Zones and Belts

14. Spot Features • Great Red Spot: • Although varying in size and color, the G.R.S. is a high pressure storm area in the S. hemisphere that has lasted at least 3 centuries. • White ovals: • Smaller regions of high pressure • Last for decades • Mostly in S. hemisphere • Dark brown ovals: • Low pressure regions • Common in N. hemisphere • Last a few years

15. The Great Red Spot

16. Motion at the Great Red Spot

17. Wind Profile of Jupiter

18. Magnetic Field of Jupiter • Jupiter has a relatively strong field of ~4.2 Gauss at “surface” • Extensive magnetosphere • Jovian version of Van Allen Belts • Jupiter Has rapid rotation, but a metallic core? Metallic hydrogen inner mantle High interior pressure leads to • Ionization of H • Crystal latticing • Free electrons Yields conductive properties similar to a metal!

19. Jovian Interiors

20. Jupiter’s Magnetosphere

21. Jupiter’s Aurorae and Magnetic Field

22. Internal Heat of Jupiter 1960’s – Jupiter found to be excessively bright in IR It emits 60% more energy than it receives from the Sun Extra heat probably cooling of interior that was heated during early phase of formation (i.e., via gravitational contraction)

23. The atmosphere of Jupiter has few heavy elements due to a) evaporation b) the lack of heavy elements in the outer solar system c) the vacuum-like power of the Great Red Spot d) gravitational settling toward the planet's center Share Question

24. Jupiter’s Ring • Discovered by Voyager 1 in 1979 • Main part only 7000 km wide • Composed of small dust particles • These only last for ~1000 yrs, and so continual replenishment is required

25. Jupiter’s Rings