1 / 32

The Gas Giants

The Gas Giants. The Gas Giants. Together they account for 99.5% of our planetary system. Size-Mass Relationship. As with terrestrials, composition can be guessed from mean density. But the high compressibility of volatiles must be accounted for

lassie
Download Presentation

The Gas Giants

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Gas Giants

  2. The Gas Giants • Together they account for 99.5% of our planetary system

  3. Size-Mass Relationship • As with terrestrials, composition can be guessed from mean density. But the high compressibility of volatiles must be accounted for • Initially, as they accrete mass they grow in radius • But at a mass of ~300 earth masses, further accretion causes the radius to decrease.

  4. Composition • T=0 K models • T>0K • Jupiter and Saturn are well matched by H+He models • Require some ice/rock as well • Uranus and Neptune are much better represented by an icy composition. • 1

  5. Recall: Moment of Inertia • The moment of inertia is a measure of degree of concentration • Related to the “inertia” (resistance) of a spinning body to external torques • Shows giant planets are centrally concentrated: cores?

  6. Shapes • Rotation induces significant flattening of compressible material

  7. Heat Balance • The average temperature of Jupiter is 160 K. Is it in thermal equilibrium? (Assume a visible albedo of 0.43, but a perfect blackbody in the infrared). • An infrared picture of Jupiter

  8. Atmospheres • Similar thermal structure to terrestrial planets • Temperature of Jupiter and Saturn is never low enough to form a methane cloud deck – which dominates Neptune and Uranus

  9. H at high temperatures and pressures • Atmosphere of Jupiter and Saturn is mostly “liquid” H2. • At very high pressures, H atoms dissociate from each other and their electrons • Forms a metallic liquid • Good conductor • Maximum of Earth-based laboratory experiments STP

  10. Interiors • Jupiter and Saturn are dominated by an atmosphere of fluid, metallic hydrogen • Neptune and Uranus are dominated by an icy mantle, probably as a fluid, conducting ocean, surrounded by a H and He atmosphere

  11. Cloud patterns • Surface features are due to forms and colourations of the highest cloud layers

  12. Magnetospheres • The giant planets have strong magnetic fields • Likely due to the convective, metallic hydrogen interior • Interact with solar wind (and atmosphere of Io) to produce spectacular aurorae

  13. Summary: The Gas Giants

  14. Break

  15. Jupiter • This shows Voyager 1's approach during a period of over 60 Jupiter days. • Notice the difference in speed and direction of the various zones of the atmosphere. • The interaction of the atmospheric clouds and storms shows how dynamic the Jovian atmosphere is.

  16. Cloud motions in Jupiter’s atmosphere • The Coriolis force diverts N-S motion into E-W motion, in distinct zonal bands (5 in each hemisphere).

  17. Infared and Optical • Regions of white in visible light are dark in infrared • internal heat is blocked by the clouds • Darkest visible bands are brightest in the infrared • seeing deeper into the atmosphere where it is hotter • Red spot also dark in IR: cool, high altitude storm

  18. Jupiter’s atmosphere • Rising air from the deeper layers cools and forms clouds as it rises; we see deeper where the high ammonia clouds have been depleted by precipitation, much as on Earth rain will often mean clearer skies.

  19. Great Red Spot • Red colour probably from red phosphorous • A large eddy caused by rising hot gas and the Coriolis force

  20. Oval BA • A White oval storm, similar to the Red Spot but smaller • Formed from colliding storms in 1998 • Recently turned Red • May be bringing material to the upper atmosphere, where reactions with UV solar rays change the colour.

  21. Oval BA • Near collision in July 2006 • Is now the size of Earth with winds reaching 645 km/s, similar to the Great Red Spot • July 2006 • Feb 2006

  22. Saturn

  23. Saturn… views never seen before • From the Cassini spacecraft http://saturn.nasa.jpl.gov

  24. Saturn… views never seen before • From the Cassini spacecraft http://saturn.nasa.jpl.gov • night side of Saturn is partly lit by light reflected from its own ring system. Earth Faint E-ring, created by fountains from Enceladus

  25. Earth from Saturn

  26. Crossing the ring plane

  27. Internal heating • Saturn radiates more energy than it receives, by the same amount as Jupiter does • But Saturn is smaller, and this cannot all be gravitational energy • It is thought that He forms droplets and sinks downward, releasing gravitational energy • Thermal infrared picture of Saturn

  28. Storm at the pole Storms on Saturn • Like Jupiter, Saturn shows large storms • These are usually harder to see, however

  29. Uranus and Neptune • Uranus • Bluish green colour, with far fewer atmospheric features than Jupiter and Saturn • Neptune

  30. Colours of Uranus and Neptune

  31. Uranus and Neptune: Interiors • Likely have a rocky core, but are dominated by a fluid, icy and ionic ocean • Surrounded by an atmosphere rich in H and He • Uranus is the only gas giant that does not emit much more heat than it receives from the Sun • Internal convection disrupted? • Consistent with lack of storms

  32. Uranus’ tilt • Uranus has an axis of rotation pointing almost directly toward the Sun • Interestingly, prevailing winds are still E-W, so the Coriolis force dominates the weather patterns.

More Related