1. GENS4001 X1The Solar System1 Lecture 2: The Solar System Dr Michael Burton

2. GENS4001 X1The Solar System2 Overview Formation from collapse of cloud of gas and dust 4.6 billion years ago. Collisions and cratering dominated for first 150 million years, leaving current planetary system. Inventory: 1 star, 8+1 planets, moons, asteroids, comets, solar wind. Terrestrial (rock)+ Jovian (gas) planets

3. GENS4001 X1The Solar System3 Our Star, the Sun Giant ball of plasma undergoing thermonuclear fusion of hydrogen in centre! Photosphere (visible), chromosphere (spicules & granules), corona (solar wind) comprise the atmosphere. Sunspots, magnetic fields and convection, causing plages, prominences & solar flares. Solar Model well understood (neutrinos?).

4. GENS4001 X1The Solar System4 Mercury Day is two years long (tidal resonance)! Cratered surface (impacts), covered by some lava flows. Iron core and magnetic field. Atmosphere (Na) from outgassing of planet.

5. GENS4001 X1The Solar System5 Venus Dante’s Inferno: 500°C, 100 atmospheres and sulphuric acid clouds! Runaway greenhouse hidden by cloud. Rolling hills, two continents and volcanoes. Crust periodically melts?! Slowly rotates backwards with no seasons.

6. GENS4001 X1The Solar System6 Earth / Moon Double planet system, tidally interacting. Plate Tectonics produces continents, oceans, mountains & volcanoes. Iron rich core producing magnetic field. Supports life on land, oceans & atmosphere. Moon created via collision-ejection. Weathering erased asteroid impacts on Earth but past history still visible on Moon.

7. GENS4001 X1The Solar System7 Mars No canals, but ancient river channels! No plate tectonics, resulting in giant shield volcanoes over hot spots, plus canyons. A few impact craters. Thin carbon dioxide atmosphere & red dust. Water must once have flowed. Could life have once existed? 2 moons are captured asteroids.

8. GENS4001 X1The Solar System8 Jupiter The Giant of the planets (not a failed star). Rapid, differential rotation. Belts & Zones, methane & ammonia clouds. Cyclones interface: Red Spot & white ovals. Strong magnetic fields, huge aurorae. Gas / Liquid Metallic H / Rocky Core. Thin, transient dust ring - meteor impacts.

9. GENS4001 X1The Solar System9 Moons of Jupiter 16 Moons with 4 giants (Galilean satellites). Io: Volcanic, molten through tidal heating. Europa: Ice, tidal heating, life in oceans?? Ganymede: Rock & Ice, past tectonics. Callisto: Rock, cratered terrain (impacts).

10. GENS4001 X1The Solar System10 Saturn Lord of the Rings. Gas giant, much like Jupiter. Razor-thin rings of icy rocks (10 cm-10 m). Gravitational resonance with moons. At least 20 moons. Titan with nitrogen & hydrocarbon atmosphere, ethane oceans - life??

11. GENS4001 X1The Solar System11 Uranus A bland gas giant. Tipped over – exaggerated seasons! Magnetic axis at 60° to rotation axis. 15 Moons, rings. Miranda: almost shattered by collision.

12. GENS4001 X1The Solar System12 Neptune A blue gas-giant, similar to Uranus. Discovered through prediction from discrepancy in motion of Uranus. Fastest winds in solar system (1700 km/hr)! 8 moons, rings. Triton captured - retrograde orbit. Extreme cold (36K) but nitrogen geysers! Being pulled into Neptune by tides!

13. GENS4001 X1The Solar System13 Pluto + Charon Not really a planet - a double moon system. Discovered by chance in 1930. Now furthest from Sun (again, just!). Rock & ice.

14. Comets and Asteroids Debris from formation of Solar System. Asteroids: lumps of rock a few km in size. Most in belt between Mars & Jupiter. Comets: primordial balls of ices and rocks: transient dirty snowballs. Highly elliptical orbits, from Kuiper Belt (50-500AU) or Oort Cloud (to 50,000AU). Tails only when near Sun (vaporised ice), blown out by the solar wind & sunlight.