Chapter 9 Planetary Geologywhy are stars and planets roundTuesday, January 15, yChapter 9 Planetary Geologywhy are stars and planets round-GravityInteriors separate int 3 layers, by density-Core: highest density; metals like nickel and iron-Mantle: moderate density; medium density rocks-Crust: lowest density, low density rocks-Differentiation- the process by which gravity separates by density• gravity pulls high density material to center• lower density material rises to surface• material ends up separated by density• Lithosphere: a plaet’s outer layer of cool, rigid rock, it “floats” on the warmer, softer rock that lies beneath• Seismic waves lik light waves, bend when density and rock properties change• Moonquakes- lunar seismometer left on the moonSize is the single most important factor in planetary cooling•Smaller worlds cool off faster and harden earlier•explains why the moon and mercury are now geologically “dead”It’s driven in part by hot interiors•wheres Heat come from?1Tuesday, January 15, y•accretion and idfferentation when planets were young•GPE concerted to thermal energy•radioactive decay is most important eat source todayWays to transfer heat•Convetion- bulk motion of material•conduction- colliding atoms and molecules•radiation- thermal emissionTerrestrial Plant interiorsWhat is a magnetic field-•a magnetic field describes a magnetic force, which is the orientation tug exhorted on other magnetsMagnetic Fields of planets•a world can have magnetic field if charged particles are moving inside•3 requirements•molten interior•convection•moderately rapid rotationVenus-Hottest planet-we can’t see the surface of venus because it’s loaded by it’s thick atmosphere-The images we have of it’s surface are made possible by radar mapping2Tuesday, January 15, y-Handful of craters• fewer craters that the moon, mercury, mars, and is younger• Many volcanos; is probably still volcanically active• no eruptions dected• Photos of rocks taken by lander show little evidence for erosion-too hot for snow or rain-thick atmosphere and slow rotation probably results in stagnant airUnique geology of earth-obviously unique-largest terrestrial world, water and water erosion, modest rotation that drives wind andweather and of course, life!-composition of continents is different than seafloor, they are made of lighter rocks that“float” higher-Seafloor is quite young whereas continents contain some of the oldest rocks on