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4/12/2015 Today’s Class: The Giant Planets – Jupiter & Its moons April 13, 2015 Homework: 1. Reading: Saturn at http://en.wikipedia.org/wiki/Saturn 2. Mankind Beyond Earth, p. 225-231. 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 Astronomy 2020 – Space Astronomy & Exploration Clicker Question: What is the leading hypothesis for Venus’ lack of water? 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. 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. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration Today’s Class Jupiter • Inside Jupiter – Source of heat – Magnetosphere • Atmosphere of Jupiter • The moons of Jupiter – Io: Active volcanoes – Europa: Possible ocean & life? Astronomy 2020 – Space Astronomy & Exploration • Much farther from Sun than inner planets • Mostly H/He; no solid surface • 300 times more massive than Earth • Many moons, rings Astronomy 2020 – Space Astronomy & Exploration 1 4/12/2015 Jupiter’s moons Inside Jupiter 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" • 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. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration Jupiter's Internal Heat Jupiter's Magnetosphere • Jupiter radiates twice as much energy as it receives from the Sun. • Energy probably comes from slow contraction of interior (releasing potential energy). • Jupiter's strong magnetic field gives it an enormous magnetosphere. • Gases escaping Io feed the donut-shaped Io torus. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration Clicker Question: Jupiter does not have a large metal core like the Earth. How can it have a magnetic field? 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. 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. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration 2 4/12/2015 Jupiter's Atmosphere Jupiter's Colors • Hydrogen compounds in Jupiter form clouds. • Different cloud layers correspond to freezing points of different hydrogen compounds. • Ammonium sulfide clouds (NH4SH) reflect red/brown. • Ammonia, the highest, coldest layer, reflects white. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration Why are Jupiter's Galilean moons so geologically active? Io's Volcanic Activity • Io is the most volcanically active body in the solar system, but why? Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration Io's Volcanoes Tidal Heating • Volcanic eruptions continue to change Io's surface. Astronomy 2020 – Space Astronomy & Exploration Io is squished and stretched as it orbits Jupiter. Astronomy 2020 – Space Astronomy & Exploration 3 4/12/2015 Europa's Ocean: Waterworld? Tidal stresses crack Europa's surface ice NASA/JPL/DLR Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration 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. Astronomy 2020 – Space Astronomy & Exploration Astronomy 2020 – Space Astronomy & Exploration 4