AST 111 Lecture Notes - Lecture 13: The Moons, Lithosphere, Inferior And Superior Planets
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AST 111: Lecture 13- The Moon and Mercury/Venus/Mars
-The Moon’s Magnetism
–There is no global magnetic field on the moon
–There used to be, as evident by the residual magnetism in the rocks
–New research shows that the moon has a massive mantle, and small liquid iron
center, and an even smaller solid iron core
oThe crust density varies from the close side of the moon to the far side
oThe thick mantle and crust form a very thick lithosphere!
The moon has no surface activity like plate tectonics or volcanism
•There are moonquakes!
oThey happen very very far down, near the molten
region
oAnother reason for recorded seismic activity could be
asteroids/comets/satellites crashing on to the moon
-The moon’s crust
–Covered in REGOLITH, aka biologically dead moon dust
–All Lunar rocks are Igneous (formed by the solidification of molten material)
–Some of these rocks are known as anorthosites, and they can be older than 4
billion years, the younger rocks are much like the volcanic rocks on earth, and
are found in the Marae
-Mercury/Venus/Mars can all be seen with the naked eye
–Mercury
oVery illusive and difficult to see!
oAt most elongation of Mercury is only 28
oThe best time to view it is at greatest elongation
oThe best way to view it is to use filters on a telescope and view it during
the day when it is high in the sky
–Venus
oThe best elongation is about 47
oAt greatest brilliance, it is the 3rd brightest object in the sky
This happens because it is cloud covered and very reflective, close
to the sun, and close to the earth
–Mars
oIs a superior planet, so it can be observed at opposition, when it is very
high in the sky
oA favorable opposition appears every 15-17 years
-Rotations
–Mercury
ohas a 3-2 spin-orbit ratio
–Venus
oVery unusual rotation
oRotates very slowly, with a sidereal period of 243 days
oThe sidereal period is 224 days, so it takes more than one revolution to
rotate once!
oIt also rotates RETROGRADE