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This Island Earth - Exploring the Solar System Reading: Marshak, Ch. 1 & 2 Sol – Giver of Life * Bright enough but not too bright; massive enough, but not too massive. * Light emitted mostly in visible spectrum Welcome to the ’Hood Odd one Out – Pluto: a dirty snowball The Gas Giants Saturn and its Moons Jupiter •2.5 x as massive as all other planets combined, but low density (Sp. Gr. ~1.3) •Composed mostly of hydrogen & helium. • Fastest spin of any planet (10 hours). • Ferocious wind storms (Great Red Spot) Io – one of just four volcanically active bodies in the solar system. Asteroid Impact! The Terrestrial Planets Mercury • No atmosphere • No hydrosphere • Tectonically “Dead” • Heavily Cratered •Slow rotation 179 days • Noontime temps 800oF; nighttime temps –280oF. Venus • Resembles Earth in size, density, mass, etc. •Tectonically Active • Dense Atmosphere 90x Earth’s air pressure • CO2-rich atmosphere • “Runaway Greenhouse”: 475oC (900oF) Mars • Tectonically “dead” today, but active in distant past. •Much smaller than Earth with <1% Earth’s atmospheric pressure • Can’t retain heat, avg. temps. Down to –125oC (-193oF). • Contains some water – mostly in polar ice. • Signs of water: rivers, oceans in past; where did water go? This Island Earth – The Just-right Planet • Close, but not too close to sun. •Size – large enough to hold atmosphere, but not too much • Tectonically active; magnetic. • Atmosphere – dense, but not too dense; unusually oxygen-rich. • Temperature – well-regulated in “livable range.” • Water in three phases, oceans. • Life! A Look Inside the Earth Oceanic Crust –Thin (~5 km); dense (3.0); lower; younger (<180 my) Rigid Lithosphere Plastic Asthenosphere Continental Crust –Intermediate composition on average; thicker (~20 – 80 km); less dense (~2.7); higher; older (up to 4.0 b.y.) Mantle – Ultramafic Rock Rigid Core – Fe & Ni Liquid Solid