moonsringsetc

moonsringsetc - Moons of Jovian Planets The Solar System...

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1 The Solar System Gas Giants Massive: M J = 318 M earth 0.001 M Sun Strongly infuence dynamics/evolution oF solar system Terrestrial Planets – (land/water/air interFace) Moons and Rings Asteroids – metals, water, other materials Small in size, but large in surFace area Intercepts sunlight – observable scattered and thermal signatures T dust 30K - 1500K (evaporation) T dust (Asteroid) ~ 160K - 200K T dust (KBO) ~ 30 - 80K Moons of Jovian Planets The Galilean Moons of Jupiter Closest to Jupiter Furthest from Jupiter (sizes to scale) Radii range from 1570 km (Europa, slightly smaller than our Moon), to 2630 km (Ganymede - largest moon in Solar System). Orbital periods range from 1.77 days (Io) to 16.7 days (Callisto). The closer to Jupiter, the higher the moon density: from 3.5 g/cm 3 (Io) to 1.8 g/cm 3 (Callisto). Higher density indicates higher rock/ice fraction. Io Europa Ganymede Callisto Io's Volcanism More than 80 have been observed. Can last months or years. Ejecta speeds up to 1000 m/s. Each volcano ejects about 10,000 tons/s Rich in S, SO 2 . S can be orange, red, black depending on temperature. Frozen SO 2 snowflakes are white. Voyager 2 (1979) Galileo (1996) Activity causes surface to slowly change over the years: Volcanic activity requires internal heat. Io is a small body. Should be cold and geologically dead by now. What is source of heat? First, Io and Europa are in a "resonance orbit": Day 0 Europa Io Day 1.77 Europa Io Day 3.55 Europa Io The periodic pull on Io by Europa makes Io's orbit elliptical. Jupiter Jupiter Jupiter
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2 Io orbital speed slower orbital speed faster - Tidal bulge always points to Jupiter. So the angle of the bulge changes faster when Io is closer to Jupiter. (exaggerated ellipse) - But Io rotates on its axis at a constant rate . - So bulge moves back and forth across surface => stresses => heat => volcanoes Europa may have Warm Ocean beneath Icy Surface 860 km 42 km Icebergs or "ice rafts" suggest broken and reassembled chunks. Dark deposits along cracks suggest eruptions of water with dust/rock mixed in (Europa’s density => 90% rock, 10% ice). Fissures suggest large moving ice sheets. Hardly any impact craters. What is source of heat? Similar to Io: resonant orbits with Ganymede and Io make Europa's orbit elliptical => varying tidal stresses from Jupiter => heat. Warm ocean => life?
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moonsringsetc - Moons of Jovian Planets The Solar System...

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