The Moon
Origins
And
Features
Lunar Formation Models
The moon is a sister world that formed in orbit
around Earth as the Earth formed.
The moon formed somewhere else in the solar
system then was captured into orbit around Earth.
Early Earth spun so fast that it spun off the moon.
Current accepted theory of the
Origins of The Moon
Impact by Mars-sized protoplanet
4.5 billion years ago
Explains:
• Chemistry
• Orbit
• High angular
momentum
About 1/6 the size
Just over ½ the density
Just over 1/10 of the gravity
Chemistry of the rocks matches
rocks found in Earth’s crust and upper mantle
Very little core
No spinning core, no magnetic poles
Earth/Moon comparisons
Mean diameter
Volume
Mass
Mean density
Surface gravity
Escape velocity
Visual albedo
Visual magnitude
Earth
12,742 km
1.08321 x 1012 km3
5.9736 x 1024 kg
5.515
9.78 m/s2
11.2 km/s
0.367
-3.86
Moon
3,476 km
2.199 x 1010 km3
7.349 x 1022 kg
3.342
1.62 m/s2
2.38 km/s
0.12
+0.21
If you could fly to the Moon at a constant speed of 1000 kilometers per hour,
which is the speed of a fast passenger jet, it would take sixteen days to get there.
Apollo astronauts reached the Moon in less than four days even though they
coasted "uphill" almost the entire distance. They got a fast start.
P
The eSun happens to be 400 times the Moon's diameter, and 400 times as far away.
r
That coincidence
means
i
363,300
km the Sun and Moon appear to be the same size when viewed from
Earth.ge A total solar eclipse, in which the Moon is between the Earth and Sun, blocks the
brighte light from the Sun's photosphere, allowing us to see the faint glow from the corona,
M
the Sun's
outer atmosphere.
e
384,400 km
a
Whenn the Moon is at apogee, it is 11% farther from Earth than it is at perigee.
This isAp far enough that it cannot entirely block the bright light, so eclipses which occur near
o are not total.
apogee
405,500 km
g
e
e
Moon’s Surface Features
The Highlands
• Highlands – light
areas, rough terrain,
small mountains
• Mostly anthracite
• (plagioclase feldspars
- lots of calcium and
aluminum)
• “In place” rocks are
4.5 to 4.3 billion years
old. The oldest part
of the Moon’s surface
The Maria (Mare)
• Lowlands – dark, smooth
(16% of surface)
• Basalt – fine grained dark
igneous rock rich in iron and
magnesium (stuff that sank
in magma ocean)
• Few hundred meters thick
• Rocks are 4.3 to 3.1 billion
years old … volcanic flows
as recently as 1 billion
years ago
Lava Tubes - Rilles
Rilles – lava tubes as seen from space
Craters
Created by impact of meteors.
Due to very little atmosphere they do not burn up and
“rain down” on the surface frequently
Tyco Crater
Young – 100 MYr
85 kilometers across
Fresh (rays) = young
At impact debris is thrown upward forming a rim and extra material splashes
Out in a circular pattern called “rays.”
Rays – bits is material thrown
Outward in all directions
Which craters are older?
Which are younger?
Lunar Soil - Regolith
No organic matter
How are they different in terms of geologic
processes?
And WHY?
NO Active wind/water erosion
Active wind/water erosion
Impacts
Impacts
NO active volcanoes
Active volcanoes
Small moonquakes
Earthquakes
NO active magnetic field
Active magnetic field
Buckets of craters
Few craters
Geologically Active!
Geologically Inactive