1. The Moon Moon - Atmosphere - Surface/Geological Features/Moon Rocks
- Interior
- Origin

2. The Moon has no atmosphere
allows us to see the surface with fine detail
escape speed is too low on the Moon
- all gas molecules can escape!
no atmospheric pressure means that water can not exist in liquid form
- only in solid or vapor
temperature variations – extreme!
- day T = 403 K = 266 F
- night T = 93 K = -292 F
- day/night are each 2 weeks long!
no weathering of the surface by water, storm
no protection from high energy solar particles, cosmic rays

3. Lunar Geological Features
Craters
~30,000 visible with small telescopes from Earth
millions visible from lunar orbiting satellites
origin: interplanetary debris
sizes: largest 100’s km
across a result of fast
moving impact rocks
of only a few km’s across!
large craters often
produce “central peak”
craters
Clavius Crater
diameter = 232 km
depth of 16,000 feet

4. Lunar Geological Features
2. Lunar “Maria” - dark, smooth regions
first thought to actually be wet areas (before we knew Moon had no atmosphere)
now believed to be smoother, younger (fewer craters) surfaces
idea is that impacts created large basin and then lava flowed over surface
relatively ‘low’ compared to highlands on moon; 2-5 km below other parts
rough mountain ranges surrounding ‘maria’ suggest large impact originally
evidence for ‘flows’ (lava?) along the smooth maria

5. Lunar Geological Features
3. Lunar Highlands
most of moon (85%) is actually covered with lighter, higher land: Highlands
predominantly on the side of the Moon facing away from Earth
roughly cratered, but no smooth lava flow ‘maria’ regions
crust must be thicker in the highland areas

6. Cratering: Age of Moon’s Surface
can use cratering patterns to determine AGE of surface
no atmosphere to protect
bombardment; no erosion by
wind/water  OLD surface
(as old as ~3 billion years)
Earth’s surface only a few
100 Myrs old (geological activity has re-surfaced planet)
highlands have many more craters; maria have fewer
craters  highlands ‘older’
The smaller the planet, the less internal heat
(geology) it will
have; less geological
activity on surface

7. A Brief History of Lunar Exploration
1959: Soviet Lunas 1, 2, 3 orbited around Moon
1960’s: US Ranger
- flyby mission
- first space pictures
- many TV cameras
: Lunar Orbiter
- 5 orbiting spacecraft
- full coverage of pictures
: Lunar Surveyor
- surveying for landing sites
- testing the “soil” (sink?)

8. Highlights from Apollo 11 mission
launch: July 16th 1969
arrival at Moon: July 20th 1969
first humans to land on the Moon
Command Module (CM):
“Columbia”
Neil Armstrong
“Buzz” Aldrin
Michael Collins

9. On July 20, 1969, after a four day trip, the Apollo astronauts arrived
at the Moon. This photo of Earthrise over the lunar horizon is one of
the most famous images returned from the space program, although
even the astronauts themselves cannot remember who actually took it.

10. First steps on the Moon July 20th 1969 - Neil Armstrong
- “Buzz” Aldrin

11. Touchdown of Moon astronauts near the coast of Hawaii on July 26th 1969

12. Lunar Exploration: Apollo Missions
Apollo 1-10: pre-landing missions (Apollo 1 module fire killed 3 astronauts while being tested)
Apollo landed (except Apollo 13, which had an explosion and returned to Earth) 12 different astronauts walked on the Moon during
Principal Scientific results of the Apollo missions:
The Moon is ancient and still preserves an early history (the first billion years) that must be common to all terrestrial planets.
The youngest Moon rocks are virtually as old as the oldest Earth rocks. The earliest processes and events that probably affected both planetary bodies can now only be found on the Moon.
Early in its history, the Moon was melted to great depths to form a "magma ocean." The lunar highlands contain the remnants of early, low density rocks that floated to the surface of the magma ocean.
The Moon is not a primordial object; it is an evolved terrestrial planet with internal zoning similar to that of Earth.
The Moon is lifeless; it contains no living organisms, fossils, or native organic compounds

13. Recent Lunar Exploration
1994: Clementine
- UV, IR, visible cameras
- possible water ice at poles
- radio waves reflected off ice
1998: Lunar Prospector
- also found evidence for ice
- crashed near pole in 1999
Currently: Smart 1 Probe
- European satellite
- ion propulsion (several months!)
- will search for water at poles

14. Moon Rocks: Sampling the Surface of the Moon
surface material: “regolith” –
pulverized by constant impacts
~2500 samples brought back
by astronauts; ~850 lbs total!!
all rocks are IGNEOUS (i.e.,
from molten processes)
totally dry rocks (no water)
all rocks older than 3 Byr

15. Moonquakes: Studying the Moon’s Interior
~ 3000 quakes/year
much lower intensity
than Earth: Richter
indicate that Moon’s
interior is more rigid than
Earth’s (some ‘plasticity’)
Seismometer placed on Moon by lunar astronauts

16. Moon’s interior structure
crust is thicker on
non-Earth facing side
iron-rich core like Earth
asthenosphere layer: somewhat pliable “plastic” layer
solid layer just below surface – no plate tectonics
smaller planet than Earth – less internal energy, less geological activity!
moon probably had a weak magnetic field early in history
- core is now solid, so no current is generated

17. Color-coded images illustrate surface geography
Clementine data
blue – lowland marias
red - highlands
Galileo data – flyby in 1989
blue – lowland marias
red - highlands

18. Theories for Origin of Moon
Fission: originally part of Earth but torn free
Problem: would have fallen back or been flung into space, not into orbit.
Fails to explain why lunar chemistry differs from Earth's
Co-Creation: formed in its present orbit
can not explain why lunar chemistry differs from Earth's
Capture: formed as a separate planet but captured by Earth
Conditions for successful capture very stringent
Impact: formed from Mega-Impact of Mars-sized planet
Computer modeling suggests SS forms 100 or so small planets, then collide to make larger objects
can explain differences in chemistry:
impact occurred after chemical differentiation in Earth; therefore, not as much iron was part of the Moon
high temperatures during impact would have vaporized the volatile and water vapor in rocks
Currently favored model

19. Computer Simulation of Formation of Moon
Moon may have
formed by a
Mars-sized object
impact on Earth
Some of the material
does not fall back
onto the Earth, but
forms a satellite
of Earth