Last Class. Today s Class 11/28/2017

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1 Today s Class: The Jovian Planets & Their Water Worlds 1. Exam #3 on Thursday, Nov. 30 th! a) Covers all the reading Nov b) Covers Homework #6 and #7. c) Review Space in the News articles/discussions. d) Covers all material discussed in class including in-class group exercises & clicker questions. e) One page (front + back) of notes allowed. Bring a calculator that is NOT on your phone. f) Study with another member in the class! 2. Review session on Nov. 29 in G130 (this room) at 4-5pm. Space in the News: First interstellar object from beyond our solar system spotted by astronomers Presenter: Alex Rosenthal Artist s impression of the first interstellar asteroid, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Last Class The atmosphere of Venus. Greenhouse Effect on Venus & Earth. How did Earth s atmosphere end up so different from Venus? Effects of water and carbon Dangers of human activity Clicker Question: What is the leading hypothesis for Venus lack of water? a) It s water molecules were broken apart, and hydrogen was lost to space. b) Venus formed closer to the Sun and accreted very little water. c) Its water is locked away in the crust along with carbon. d) Active volcanoes absorbed all the water early in the evolution of Venus. Clicker Question: What is the leading hypothesis for Venus lack of water? a) It s water molecules were broken apart, and hydrogen was lost to space. b) Venus formed closer to the Sun and accreted very little water. c) Its water is locked away in the crust along with carbon. d) Active volcanoes absorbed all the water early in the evolution of Venus. Today s Class Inside Jupiter Source of heat Magnetosphere NASA s JUNO mission The moons of Jupiter Io: Active volcanoes Europa: Possible ocean & life? The Saturn System Titan Enceladus NASA s Cassini mission 1

2 Jupiter Much farther from Sun than inner planets Mostly H/He; no solid surface 300 times more massive than Earth Many moons, rings Jupiter s moons Jupiter's moons can be as interesting as planets themselves, especially Jupiter's four Galilean moons. Io (shown here): active volcanoes all over Europa: possible subsurface ocean Ganymede: largest moon in solar system Callisto: a large, cratered "ice ball" Inside Jupiter Jupiter's Magnetosphere High pressures inside Jupiter cause phase of hydrogen to change with depth. Hydrogen acts like a metal at great depths because its electrons move freely. Jupiter's strong magnetic field (20,000 times Earth!) gives it an enormous magnetosphere. Gases escaping Io feed the donut-shaped Io torus. Clicker Question: Jupiter does not have a large metal core like the Earth. How can it have a magnetic field? a) The magnetic field is left over from when Jupiter accreted. b) Its magnetic field comes from the Sun. c) It has metallic hydrogen inside, which circulates and makes a magnetic field. d) Its core creates a magnetic field, but it is very weak. Clicker Question: Jupiter does not have a large metal core like the Earth. How can it have a magnetic field? a) The magnetic field is left over from when Jupiter accreted. b) Its magnetic field comes from the Sun. c) It has metallic hydrogen inside, which circulates and makes a magnetic field. d) Its core creates a magnetic field, but it is very weak. 2

3 Juno Solar-powered, spinning spacecraft 8 Science instruments Proposed/selected 2005 Launched Aug 5th 2011 Arrived Jul 4th 2016 The Juno Spacecraft Juno s key components: Solar arrays 2m x 7.5m arrays producing ~300 W Sun-pointed, spinning 2 rpm Waves Radio & plasma Spacecraft & Payload JunoCam camera UVS UV spectrometer JIRAM IR spectrometer Gravity Science SPACECRAFT DIMENSIONS Diameter: 66 feet (20 m) Height: 15 feet (4.5 m) JEDI High-energy particles JADE Low-energy particles Magnetometer Juno: Close Polar Orbit is Key 35 polar orbits MWR Microwaves Duck under radiation belts Skim above clouds Why are Jupiter's Galilean moons so geologically active? 3

4 Io's Volcanoes Europa's Ocean: Waterworld? Volcanic eruptions continue to change Io's surface. NASA/JPL/DLR Tidal stresses crack Europa's surface ice Europa's interior also warmed by tidal heating Possible Robotic Mission to Europa Goal: JPL s Europa Clipper is a concept that would conduct detailed reconnaissance of Jupiter's moon Europa and would investigate whether the icy moon could harbor conditions suitable for life. Mission would perform detailed investigation of Europa using a radiation-tolerant spacecraft that would perform repeated close flybys of the icy moon from a long, looping orbit around Jupiter. Saturn Giant and gaseous like Jupiter Spectacular rings Many moons, including cloudy Titan 4

5 Rings are NOT solid; they are made of countless small chunks of ice and rock, each orbiting like a tiny moon. Saturn Medium and Large Moons Enough self-gravity to be spherical Have substantial amounts of ice Formed in orbit around jovian planets Circular orbits in same direction as planet rotation Titan's Atmosphere Titan's Surface Titan is the only moon in the solar system to have a thick atmosphere. It consists mostly of nitrogen with some argon, methane, and ethane. Huygens probe on Cassini provided first look at Titan's surface in early It found liquid methane and "rocks" made of ice. Enceladus Geysers of Water NASA s Cassini Mission Ice fountains of Enceladus suggest it may have a subsurface ocean. 5

6 NASA s Cassini Mission: The End 60º N Cassini s Final Hour 50º N Saturn's Atmosphere 40º N 30º N 20º N 10º N Measurements of: Exosphere/Thermosphere Ionosphere Ring rain Magnetic Field What did we learn Today? Inside Jupiter Source of heat Magnetosphere NASA s JUNO mission The moons of Jupiter Io: Active volcanoes Europa: Possible ocean & life? The Saturn System Titan Enceladus NASA s Cassini mission 6