AST 309 Chapter 7: Chapter Seven Notes

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Department
Astronomy
Course
AST 309
Professor
Finkelstein Keely
Semester
Spring

Description
ChapterSeven Notes Friday, March 17, 2017 2:29 PM 7.3 Dating Planetary Surfaces • The age of thesesurfaces is not necessarily theage ofthe planet as a whole. Geologically activeobjectscan have planetweatheringwhicherasesevidenceof earlierepochsandpresentsuswithonlyarelativeyoungsurfaceforinvestigation Counting the Craters • Works becausethe rateat whichimpactshave occurred in thesolar systemhas beenroughlyconstantforseveralbillionyears.So,thenumberofcratersis proportionaltothelengthoftimethesurfacehasbeenexposed. • Crater counts can onlytellus the time since thesurfaceexperienced a major changethatcouldmodifyorerasepreexistingcraters. Radioactive Rocks • Measure the ageof individual rocks. ○ Using the propertiesofnatural radioactivity. § Half-life:aspecifictimeperiodduringwhichthechancesare fifty0fifty thatdecaywilloccur for any of thenuclei • Radioactive elements withhalf-liveswe have determinedcanprovide accurate nuclearclocks. • The decay ofradioactivenuclei generallyreleases en
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