p.4-2SP0051 – AstronomyPre-Class Reading (The Cosmic Perspective)Chapter 91 Connecting Planetary Interiors and Surfaces2 Shaping Planetary Surfaces3 Geology of the Moon and MercuryWhat geological processes shaped Mercury4 Geology of Mars5 Geology of VenusChapter 104 The Atmospheric History of Mars5 The Atmospheric History of Venus
p.4-3SP0051 – AstronomyAxis Tilt of Terrestrial Planets
p.4-4SP0051 – AstronomyInterior Structure of Terrestrial WorldsAll terrestrial worlds havedistinct layering.due todifferentiation(at some time in the past) – process wheregravity separates materials by density when the object ishotLithospheric thicknessis closely related to planetarysize.
p.4-5SP0051 – AstronomySource of Internal HeatTerrestrial planetswerehotwhenthey wereyoung.Radioactive decaystill supplies heatto the terrestrialinteriors but at alower level thanwhen the planetswere young.
p.4-7SP0051 – AstronomyGeological ProcessesTerrestrial surface featuresare due to:Impact cratering– excavation ofbowl-shaped craters by asteroids orcomets crashing into the surfaceVolcanism–eruptionofmoltenrock, or lava, from its interiorTectonics– disruption of surface byinternal stressesErosion–wearingdownorbuilding up of geological featuresbywind,water,ice&otherplanetary weatherDue toplanet itselfDue to anexternal cause
p.4-8SP0051 – AstronomyImpact CrateringImpacting asteroid or comet typicallyhit surface at40,000~250,000 km/hr.vaporizesolid rock & blast out acircularcrater ~10 times as wide as object & 1~2times as deep as the size of objectMeteor crater (~ 1km across & 200m deep) in Arizona created~50,000 years ago by a metallic asteroid ~50m across.
p.4-9SP0051 – AstronomyMany impact craters on Earth, and especiallyMoon&Mercury.most happenedsoon aftersolar system formedsmallcratersoutnumberlarge ones (many more small objects)Most ancient craters on Earth wereerasedbyvolcanicactivity&erosion.themorecraters, theolderthe surfaceImpact Cratering, cont’dTycho crater on the MoonGalle crateron Mars
p.4-10SP0051 – AstronomyVolcanismVolcanic eruptionoccurs when undergroundmoltenrock(magma) finds a path to the surface (lava).Volcanism produces volcanicmountains& explainsexistence of ouratmosphere&oceans.icy planetesimalstrappedbeneath surface after impacteruption release some of the water (outgassing) to make Earth’satmosphere & oceansRunny lavamakesflatlava plains.