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The Moon Week 2 part 2 Thursday, January 13, 2011 Two ways to look at it The Moon from the point of view of Earthlings (phases) The Moon as a solar system body (what the astronauts saw) Thursday, January 13, 2011 The formation of the moon: Impact hypothesis something large (same size as Mars) hit Earth and knocked off a chunk of Earth’s mantle Much of splattered Earth coalesced into the moon The Mars-sized something was completely destroyed and probably merged with Earth’s core Thursday, January 13, 2011 The formation of the moon: Impact hypothesis something large (same size as Mars) hit Earth and knocked off a chunk of Earth’s mantle Much of splattered Earth coalesced into the moon The Mars-sized something was completely destroyed and probably merged with Earth’s core Thursday, January 13, 2011 moon How do we know? Thursday, January 13, 2011 How do we know? We’ve been there... Thursday, January 13, 2011 How do we know? We’ve been there... observations Thursday, January 13, 2011 explanation How do we know? We’ve been there... observations tested soil composition same as Earth’s mantle and crust (mostly silicates) Thursday, January 13, 2011 explanation How do we know? We’ve been there... observations tested soil composition same as Earth’s mantle and crust (mostly silicates) made “moonquakes” to determine layers (mantle layer very thick) Thursday, January 13, 2011 explanation How do we know? We’ve been there... observations tested soil composition same as Earth’s mantle and crust (mostly silicates) made “moonquakes” to determine layers (mantle layer very thick) see lots of craters and some “maria” Thursday, January 13, 2011 explanation How do we know? We’ve been there... observations explanation tested soil composition same as Earth’s mantle and crust (mostly silicates) moon formed from molten mantle of Earth made “moonquakes” to determine layers (mantle layer very thick) see lots of craters and some “maria” Thursday, January 13, 2011 How do we know? We’ve been there... observations explanation tested soil composition same as Earth’s mantle and crust (mostly silicates) moon formed from molten mantle of Earth made “moonquakes” to determine layers (mantle layer very thick) see lots of craters and some “maria” Thursday, January 13, 2011 used to have liquid core and had lava flows on surface How do we know? We’ve been there... observations explanation tested soil composition same as Earth’s mantle and crust (mostly silicates) moon formed from molten mantle of Earth made “moonquakes” to determine layers (mantle layer very thick) see lots of craters and some “maria” Thursday, January 13, 2011 used to have liquid core and had lava flows on surface now is geologically dead (no more flows, no liquid center?) Fun facts Mass 1/83 Earth’s mass no magnetic field radius 1/4 Earth’s radius “tidally locked” always shows the same face to Earth, so Earth only visible from one side of moon gravity 1/6 Earth’s gravity no atmosphere no water (but maybe a little ice) Thursday, January 13, 2011 yes, we really went there Earthlings’ point of view Always see the same side see different parts of the face Thursday, January 13, 2011 month <- moon exhibits phases extremely regular (always takes the same amount of time to get back to a given phase) moon doesn’t shine - only reflects sunlight moon orbits Earth Thursday, January 13, 2011 Thursday, January 13, 2011 Who’s rotating? Thursday, January 13, 2011 Which is the near side and which is the far side? (ignore the size difference - the images came from 2 different places online) Thursday, January 13, 2011 Resources http://www.braeunig.us/space/hoax.htm http://www.xmission.com/~jwindley/ Thursday, January 13, 2011