The Gas Giants

Jupiter

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) 1 st 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

Jupiter from the Shadow Side

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: H 2 O water CH 4 methane NH 4 ammonia Appearance: complex gas dynamics alternating dark belts and bright zones

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.

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

Jupiter’s Atmospheric Structure

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

Appearance of Jupiter at Long Wavelengths Jupiter at IRJupiter at Radio

Jupiter’s Dynamic Atmosphere and UV Aurorae

Zones and Belts

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

The Great Red Spot

Motion at the Great Red Spot

Wind Profile of Jupiter

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!

Jovian Interiors

Jupiter’s Magnetosphere

Jupiter’s Aurorae and Magnetic Field

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)

Share Question 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

Jupiter’s Ring oDiscovered by Voyager 1 in 1979 oMain part only 7000 km wide oComposed of small dust particles oThese only last for ~1000 yrs, and so continual replenishment is required

Jupiter’s Rings