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November 12th 2012 - Lecture notes.docx

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John Lester

Astronomy Lecture Notes October 12 2012 Friday’s Lecture - Moon: slow rotation, solid, rocky core  no field. - Mercury: slow rotation and solid but metallic does not have a magnetic field. - Mars: weak gravity but cool temperature  atmosphere. - Atmosphere: mostly CO2 because no rain to wash it out, no plants to convert it. - No erosion  heavily cratered. - Interior: small, metallic core, probably solid  No magnetic field, no continental drift. - Surprises: Huge volcanoes, large rifts, evidence of flowing water, ice. - Venus: a twin of Earth? Is Venus a twin of Earth?  NO! not even close.  Atmosphere: 96% CO2 (not O2 or N2).  Surface temperature: 470 degree Celsius (743 K)  hotter than pizza oven. Why is Venus so different?  It is slightly closer to the Sun than Earth, makes a big difference. o Have volcanoes that we assume to emit CO2 and H2O like Earth’s volcanoes.  But Venus is too HOT for liquid water to form…  No rain to wash CO2 from atmosphere.  CO2 is a powerful GHG  Makes it much hotter. NOTE: Earth’s rocks have as much CO2 as Venus has in its atmospheres  Rain removed that much CO2 from our atmosphere. ALL of this because Venus is a bit closer to the Sun.  Extreme heat  no water, rain, or oceans. o No plants to convert CO2 to O2 o Without O2  no ozone (O3)  Cannot block ultra violet radiation.  Ultraviolet radiation blocks H2O molecules in the atmosphere  Hydrogen and Oxygen atoms. o Hydrogen escapes to space. o Oxygen binds with soil. What is the surface of Venus like? Problem: the atmosphere is very thick and cloudy  we can’t see the atmosphere.  The surface temperature is so hot and the pressure is so high that all landers fail quickly. SOULUTION: using satellites orbiting Venus to study the surface using radar to see through.  Volcanoes and lava flows o Consistent with Venus’ size and mass. Astronomy Lecture Notes October 12 2012  Large impact craters o Not eroded by water, ice, wind  Almost no signs of continental drift o No mountain range o Few faults or rift  VERY different from Earth.  Maybe continental drift needs water to lubric
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