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Homework 7 will be posted shortly YU55 If it had struck land, it might have caused a magnitude seven earthquake and left a city-sized crater. If it has struck the ocean, it would have raised a large tsunami. Jupiter’s Galilean Satellite’s Orbital resonances among Galilean Satellite’s Io Io’s Volcanoes The most volcanically active world in the solar system. Europa: An ice-covered world Europa: Heated by tidal friction Europa – Tidal heating, similar to IO but weaker – Young cracked water ice crust perhaps only a few kilometers thick – Thought to have a warm ocean of salty liquid water below its crust. – life? – Icebergs ice cliffs Grooves & channels Glaciers? Earth: arctic ocean Earth: arctic ocean Europa’s interior warmed by tidal heating. Internal structure derived from measurements taken by spacecraft in the Jovian system. Salty - Europa has a magnetic field Sub-Crust Ocean .. . Hydrogen-Carbon compounds likely: Amino acids First New Ocean Life in the Ocean? Since Balboa Life in the Ocean? Conditions are consistent with the . presence of volcanic . vents .(black smokers) at bottoms of ocean. Life could have developed there. Life in the Ocean? Complex life? Probably requires oxygen High energy particles from Jupiter Collisions disassociate water H H O Hydrogen lost to space, oxygen absorbed by ice H O H On timescale of several million years, oxygen moves through ice to ocean Missions to Europa http://www.jpl.nasa.gov/europaorbiter/ Ganymede Ice-covered moon Craters and pressure ridges Ganymede • Largest moon in the solar system • Clear evidence of geological activity • Tidal heating expected - but is it enough? Ganymede Wrinkles due to tectonic movement in ice crust in (distant) past possible water deep below? Model of Ganymede's interior: cold rigid ice crust outer warm ice mantle inner silicate mantle metallic core. Ganymede • Cratering – Dark areas: cratering upon cratering several byr old – Bright areas: far fewer craters and grooves – Explanation: “lava” (i.e., water) eruptions followed by freezing • Ocean? – Magnetic field convecting core – Part of magnetic field varies with Jupiter’s rotation electrically conducting interior (brine?) – Salts found on the surface • Heat source – Less tidal heating than Europa (larger distance from Jupiter) – Large mass more radioactivity – Much less heat than in Europa thick crust (>150 km?) Much harder to prove the existence of life, never mind finding it Callisto • “Classic” cratered iceball. • No tidal heating no orbital resonances. • But it has magnetic field! This is not understood. Callisto Scarp close up Callisto Possible water deep? Callisto • Cratering – Heavily cratered everywhere no water gushing to the surface • Gravity – Undifferentiated: mix of ice and rock throughout • Induced magnetic field – Exists underground ocean? Not clear. • Heat source? – Does not participate in the tidal resonance – Radioactive decay: only possibility for heating of interior Given our discussion of tidal synchronization of the rotation and orbital periods, what might this say about planets and stars? (red) (yellow) (green) (blue) nothing planets close to stars will have synchronized rotations planets far from stars will have synchronized rotations it will depend upon the composition of the planet Given our discussion of tidal synchronization of the rotation and orbital periods, what might this say about planets and stars? (red) (yellow) nothing planets close to stars will have synchronized rotations Life beneath the surface of Europa would most likely obtain energy from (red) (yellow) (blue) (green) the Sun Jupiter radioactivity tidal heating Life beneath the surface of Europa would most likely obtain energy from (re) (yellow) (blue) (green) the Sun Jupiter radioactivity tidal heating Life in the subsurface ocean of Europa will most likely consist of (red) creatures similar to seals and penguins which enter the ocean through holes in the icy crust (yellow) plants on the ocean floor (green) simple single-celled organisms (blue)fish and other complex aquatic organisms Life in the subsurface ocean of Europa will most likely consist of (red) creatures similar to seals and penguins which enter the ocean through holes in the icy crust (yellow) plants on the ocean floor (green) simple single-celled organisms (blue)fish and other complex aquatic organisms Life on Galilean Moons? • Io X • Europa Very active volcanically. Hostile environment ? • Ganymede Subsurface saline ocean, hydrothermal vents? ? Subsurface saline ocean? hydrothermal vents? • Callisto saline ?? Subsurface ocean?