lecture12_Moon_2011_as_given

lecture12_Moon_2011_as_given - Announcements Midterm next...

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Announcements Midterm next class – be on time; bring pencils – 50 MC, 9 short answer Review session today! 4:00-6:00 in Young CS76. Field trip sign up --- after class, no deposit needed Quiz #6 – answers. Error catching. Writing Assignment. Outlines due this week “Ocean Worlds of the Outer Solar System” Dr. Kevin Hand - NASA Jet Propulsion Laboratory Thursday, 4:00 – 5:00 in Geology 3653
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Lecture 12: Making an Impact! Radioactivity, meteorites and the Age of the Solar System Age of the Earth Formation of Moon Early history of Earth, as revealed by the Moon Our goals today: Artist’s conception depicting the origin of the Moon in a huge collision between the Earth and a planet half its size.
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most meteorites are chondrites: primitive, undifferentiated solar nebula samples “chondrite” “achondrite” iron stony-iron stones
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Meteorites and the Solar Nebula Meteorites come from asteroids - small bodies orbiting (mostly) between Mars and Jupiter Almost 90% of meteorites (falls) are chemically undifferentiated: “primitive” Therefore, most asteroids are undifferentiated - stayed as small bodies How old are they?
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Chart of the Nuclides (isotopes) Z N
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Stability Nuclear stability is the exception rather than the rule (i.e., only ~260 of ~1700 known nuclides are stable) Chart of the Nuclides arrays nuclides in terms of neutron and proton numbers. As mass increases, the ratio of neutrons to protons rises from 1 to 2 Stable nuclides form a narrow band (the ‘valley of β stability’) bounded by unstable nuclides. Valley of β stability is energy trough into which unstable nuclides fall to lowest energy state Unstable nuclides decay by emitting particles from their nuclei, i.e., they are “radioactive”. The loss of α or β particles changes the proton number, thereby transmuting the radioactive isotope into another chemical element.
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Radioactive decay occurs at a constant rate – provides the basis for a clock.
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lecture12_Moon_2011_as_given - Announcements Midterm next...

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