Transcript Lunar Exploration slides

•Lunar Rocks
•Lunar Interior
•Lunar Structure
•Lunar Formation
•Lunar Chronology
•Lunar Geology
•Lunar Exploration
Lunar Rocks
Lunar Rocks
Basic classification
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Elements - individual
atom species that are
the basic building
blocks of ordinary
matter
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Minerals - are
composed of elements
or compounds of the
elements, and are often
designated by the most
common
atoms/molecules
contained in that
mineral
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Rocks - composed of
combinations of
minerals/elements and
can be classified into
three major types on
Earth: sedimentary,
metamorphic and
igneous
Lunar Rocks
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Because the Moon is small and there is no atmosphere,
water is missing from the compounds that make up
lunar rocks
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Sedimentary rocks are also not found on the Moon
because there is no water or wind
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There are similarities in the lunar rocks and those found
on Earth, including metal oxides, silicates, as well as
some carbonaceous rocks
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The lack of pure metal oxides on the lunar surface which
has no atmosphere does not exclude metal oxides that
can be formed by the accretion of the planetesimal
building blocks, and from igneous activity
Lunar Rocks
Lunar rock samples
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During the Apollo program, 382 kg (842 lb) of Moon rock
and "soil" was returned to Earth with most of the material
composed of igneous rock, meaning it originates from the
molten interior
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More recent measurements of the Moon's surface near the
southern polar region that came from Clementine, Lunar
Prospector, LCROSS, and Lunar Reconnaissance Orbiter
spacecraft indicate ice deposits on or just under the lunar
surface
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The wide variety of minerals and elements in the Apollo
rock samples contained can be simplified into three rock
types: basalt, breccia, and anorthocite
Lunar Rocks
Basalt
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Basaltic lava, or basalt, like the volcanic
lava on Earth, is rich in olivine and
pyroxene, and several elements which
enhance the dark color of the rock,
including titanium
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Basalt forms when magma flows onto the
surface of the Moon, cools and then
crystallizes
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Basalt lava flows are the dark materials
that have filled the lowlands on the
Moon's surface which cover about onequarter the Moon's surface area
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The basalt flows are generally 3.1 to 3.8
billion years (Gigayears, or Gy) old
Lunar Rocks
Breccia
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Also found on Earth but in a different
formation process, breccia rock is made
of fragments of other rocks fractured
and/or fused by collisions of meteoroids
with the Moon
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Fragments heated by the collisions that
broke them apart melted and stuck to
other grains composed of broken rocks
and smaller mineral grains
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Most breccias were produced when the
original crust of the Moon was completely
broken up by meteoroid impacts in its
early history
Lunar Rocks
Anorthocite
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Anorthosite, also found in abundance on
Earth, is a light-colored rock composed
mostly of crystals of the mineral feldspar primarily silicates
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Anorthosite rocks make up much of the
highlands of the Moon, with the feldspars
producing the light color
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The first feldspar crystals were pale gray or
colorless and later broken into fragments;
the resulting shattered feldspar crystals
produced the whitish color
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Anorthosite represent the oldest formations
on the Moon and are generally 4.0 to 4.3 Gy
old
– The "Genesis Rock" brought back by the
Apollo 15 astronauts, for example, was
one of the oldest samples at 4.6 Gy
Lunar Structure
Lunar Stats
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Mass
Radius
Mean density
Orbital eccentricity
Orbit inclination
Semimajor axis
Orbit period
Rotation period
Magnetic field
Albedo
Atmosphere
7.349x1022 kg (1/81 MEarth)
1,738 km (equatorial) (0.27 REarth)
3.35 g/cm3
0.055
5.14o (from Earth's equator)
384,400 km
29.5 days solar (27.3 days sidereal)
29.5 days
<0.0001 Gauss
0.12
Trace amounts of helium, argon, sodium, and
potassium
Lunar Interior
The Moon's 1,734 km radius spans an
iron core approximately 300 - 425
km thick, a mantle approximately
1,000 km wide, and a relatively
thick crust that ranges from tens
of km to 100 km deep, with an
average of 45 km
Estimates of the lunar interior are
primarily based on seismic data
collected during and after the
Apollo missions, and satellite data
from various lunar orbiter
missions
Seismic wave propagation and wave
refraction were also used to
constrain density, pressure values
of the interior, as well as the most
likely chemistry located at/near
the discontinuities between the
three layers
Lunar Highlands
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The Moon's early molten
mantle that is often referred to
as the "magmatic ocean“
began cooling and separating
with lighter-weight plagioclase
rising to the surface to shape
the lunar crust
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The Moon's original
plagioclase crust identified as
highlands because of its
generally higher elevation
experienced an intrusion of
slightly heavier magnesiumrich magma that contained less
plagioclase and more olivene
and pyroxene
Lunar Highlands
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These later intrusions were also
richer in potassium (K),
phosphorous (P), and rare-earth
elements (REE), and as such are
identified by the acronym KREEP
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Crust formation ended 4.1 billion
years ago when the upper-mantle
solidified
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These later formations constitute
about ¼ of the highland regions,
yet provide insight into the
formation and early evolutionary
processes of the Moon
Lunar Maria
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Heavy bombardment of the lunar surface continued until
approximately 3.9 billion years ago
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The violent impacts not only cratered the lunar surface
permanently, but created a layer of rubble, growing
deeper and more fragmented with time – lunar regolith
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As planetesimal impacts began to wane, the insulation
properties of the thickening crust and continuing
radioactivity decay began heating the interior
Lunar Maria
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At approximately 3.9 billion years, the fractured, cratered,
and thinning crust, although less dense than the mantle,
placed enormous pressure on the molten magma below,
forcing it to flow through the fissures into the lower
basins of the largest and deepest craters
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The darker, denser magma (containing dark colored
olivene and pyroxene) cooled after filling the lowest
regions, forming large regions outlined by the largest,
oldest, deepest crater basins
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These vast areas called maria, or seas, have distinctly
different geological appearance and composition
Lunar Maria
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The most distinctive
difference is the dark,
smooth surface of the
mare compared to the
rough highlands
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Because the impacts
declined in size and
number, the younger lunar
mare show fewer large
craters than the highlands
Lunar Formation
Lunar Surface Composition
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Anorthocite, which is predominantly aluminum-calcium silicates,
offers a greater abundance of both calcium and aluminum than in the
Earth's crust
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These two important elements can be employed in lunar outpost
construction and manufacturing
– A variety of other materials and elements can be produced from
anorthocite, including silica glass (silicon oxides), pure silicon,
calcium oxide (lime), and alumina (aluminum oxide)
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Basalt is composed of a broad combination of silicate and oxide
minerals that are rich in magnesium, iron and titanium
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These minerals are commonly metal oxides (MgO, TiO, FeO),
combined with silica
Lunar Surface Composition
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One of the more common
metal oxide silica minerals in
the lunar basalts is olivene,
which is a combination of
magnesium oxide plus silica
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A very important and
abundant lunar surface
mineral is ilmenite (FeTiO3)
that is important because of
its oxygen content
– Useful as a propellant and
for breathing
– Titanium content can be
used for high-temperature
and light-weight structural
metal
Lunar Magnetic Field
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The lack of a significant magnetic field on the Moon suggests a solid
or nearly solid core if one assumes a traditional geodynamic
magnetic field
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The magnetized surface rock indicates a very small but measurable
lunar magnetic field at various times during the crustal rock
formation
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Slight magnetization also appears in the highlands, possibly due to
impact shock
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Previously magnetized rock helps establish the time of crustal
formation and the approximate period of the core's dynamical motion
Lunar Formation
Lunar formation constraints on physical models (theories)
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Ratios of oxygen isotopes (O16/O17/O18) in the Earth and the Moon are
the same
The Moon and the Earth have differences in various other isotopic
ratios
The Earth's density is 5.5 g/cm3 and the Moon's is 3.3 g/cm3
The Moon crust is ~12% iron while the Earth’s is ~4%
The mantles of the Earth and the Moon have distinctly different
iron/nickel/cobalt metal (siderophile) signatures
Refractory (high-temperature) element concentrations are higher in
the Moon than in the Earth, however, their ratios are the same
Angular momentum of the Earth-Moon system is higher than any
known planet-satellite system
The Four Basic Theories of Lunar
Formation
1.
2.
3.
4.
Capture
Coaccretion
Fission
Collision
Lunar Formation
1. Lunar capture
The Earth and Moon would both be in heliocentric orbits
with a gravitational capture of the Moon by the Earth as
the Moon passed by (but needs something to remove
binding energy)
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Attractive because of its simplicity
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Easily dismissed because of the different composition
abundance of Earth and Moon (especially iron)
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Also has difficulty because of the binding energy would
be much smaller than observed
Lunar Formation
2. Coaccretion
As the Earth accumulates (accretes) planetesimal material from
bombardment in its early formation, it is possible that a smaller
body could be created in the same region from the same material
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Attractive because of simplicity and the lack of a unique,
catastrophic event
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Highly improbable because the actual composition differences
between Earth and the Moon are not accounted for
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Not possible, or certainly improbable, because the orbital angular
momentum is too small for this mechanism when compared to
the Earth-Moon angular momentum
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Also low probability since a merger is more likely than a
separate, lightly-bound Earth-Moon pair
Lunar Formation
3. Fission of a rapidly spinning Earth
During the Earth's early formation stage, growth by planetesimal
impacts generate sufficient heat to produce a liquid or semiliquid mantle. If the Earth were spinning fast enough, and
resonant low-frequency vibrations in the molten Earth could help
eject sufficient mass, the Moon could fission or break away from
the Earth
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Attractive because it can explain composition differences in the
Earth and the Moon
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Validation of a fissioning planet is difficult to model numerically
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Highly improbable because the angular momentum required to
spin off the Moon is much greater than observed
Lunar Formation
4. Collision of large body/small planet with the Earth
A roughly Mars-sized object impacting the Earth would
produce a ring of debris that could colease or accrete to
form the Moon
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Attractive because it can account for composition
differences between Earth and the Moon
– Resulting Moon would be less dense than Earth overall
since the lower-density mantle of the Earth would be
ejected
– Actual Moon has a reduced iron/metal core (7% vs.
30% for Earth)
Lunar Formation
4. Collision of large body/small planet with the Earth (cont.)
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Details of the theory have been simulated, although
several questions remain
– Nearly circular orbit of the Moon is difficult to
reproduce except under very specific impact
parameters
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This is the most probable of formation theories
considering:
– Moon's lower-iron surface composition
– Lunar core mass and density
– Oxygen radioisotope similarities between the Moon &
Earth
– High orbital angular momentum
Lunar Chronology
Lunar Chronology
4.6 By
 Layer of silicate & plagioclaise crust floats on more dense liquid magma
during early lunar formation
 Heavier olivine, pyroxene, and ilmenite (FeTiO3) sank, forming a source
for the later mare basalts
4.4 By
 KREEP rocks [potassium (K), rare-earth elements (REE), phosphorous
(P)] form as upper liquid mantle crystallizes
 Intense meteoric bombardment reduces much of highlands to rubble as seen in Apollo samples
 FeO and silica material remaining after magma solidifies moves into
lower crust, forming KREEP-like basalt regions in later basalt flows
3.9 By
 Remelting or partial melting produces maria volcanism (effusive, not
eruptive). These flows fill large basins produced by earlier, intense
bombardment
– Remelting/partial melting due to radioactive processes in the interior and
insulating crust
Lunar Chronology
3 By
 End of igneous (lava flow) activity and mare formation
 Continuing but reduced meteoric bombardment (reduced in size
and number)
 Mass range of bombarding material from 10-15 to 1020 g
 The Moon is no longer active
3 By to present
 Surface processes include meteoric activity (fracturing of surface
rock and formation of regolith) and radiation (solar wind and
cosmic rays) embedded in surface rock and soil
Some general remarks
– More than 99% of lunar surface is older than 3 By
– More than 70% of lunar surface is older than 4 By
– Nearly 80% of Earth's surface is less than 200 My old
Lunar Geology
Lunar Geology
Regolith
Regolith is the broken rock and dust layer that covers
the entire Moon, arising from repeated impacts over
its lifetime
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This layer covers entire surface to a depth of several
cm to 100 m
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Churned by micrometeoroids over billions of years
exposing subsurface material
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Exposed to space environment which allows
radioactive dating of the lunar surface and the solar
emissions
Lunar Geology
Craters
Basic structure of
the crater varies
with the
complexity of
the crater
Complex crater
features include:
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Floor
Central peak
Rim
Rim terrace
Rim deposits
Rim crest
Crater ejecta
Lunar Geology
Mountains
Lunar highlands that appear as
mountains are not true mountains
created by uplifting as on Earth,
but caused by the cratering of
highlands rock
These formations were produced
during the early formation period
(after crust development)
Generally two types:
 Regions uplifted by crustal
deformation primarily from
impacts
 Chains formed by coincidental
positions of impact crater rims
Lunar Geology
Ridges/ridge lines
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Commonly represent crater ridges
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Formed also from fractures and faulting as
Moon shrank
Lunar Geology
Valleys (rills)
Valleys can form from several
mechanisms:
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Lava channel shrinking
after its flow subsides
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Fracture lines from crust
shrinking
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Relatively narrow and long
Lunar Geology
Volcanic outflow
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Seas (Mare - Latin for seas)
– Cover 17% of lunar surface
– Thick crust slows flow
– Some small cone volcano
formations are seen on the
Moon
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Volcanic cones (what is often
seen on the Earth)
– Very few on lunar surface
– Relatively small in size
– Glass material found in
surrounding ejecta
– Much less dramatic than
lava floods that produced
maria
Lunar Geology
Far-side of the Moon
The Moon’s far side was first
seen in the images returned
from Russia’s Luna 3 probe
launched in October, 1959
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Distinctly different geology
since the lunar core was
displaced toward Earth due to
synchronous rotation
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Thinner crust on the near side
(facing Earth) had far more
mare than the far side of the
Moon
Lunar Exploration
Lunar Exploration - Early
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Pioneer 0 - USA Lunar Orbiter - (August 17, 1958) - Failed
Pioneer 1 - USA Lunar Orbiter - (October 11, 1958) - Failed
Pioneer 3 - USA Lunar Flyby - (December 6, 1958) - Failed
Luna 1 - USSR Lunar Flyby - 361 kg - (January 2, 1959) - First lunar flyby
Pioneer 4 - USA Lunar Distant Flyby - 5.9 kg - (March 3, 1959) - Failed
Luna 2 - USSR Lunar Hard Lander - 387 kg - (September 12, 1959) - first spacecraft to impact the Moon
Luna 3 - USSR Lunar Far Side Flyby - 278.5 kg - (October 4, 1959) - First images of the Moon's far side
Ranger 3 - USA Lunar Hard Lander - 327 kg - (January 26, 1962) - Failed
Ranger 4 - USA Lunar Hard Lander - 328 kg - (April 23, 1962) - First US lunar impact of the Moon
Ranger 5 - USA Lunar Flyby - 340 kg - (October 18, 1962) - Failed
Luna 4 - USSR Lunar Probe - 1,422 kg - (April 2, 1963) - Failed
Ranger 6 - USA Lunar Hard Lander - 361.8 kg - (January 30, 1964) - Failed
Ranger 7 - USA Lunar Hard Lander - 362 kg - (July 28, 1964) - First closeup images of the Moon
Ranger 8 - USA Lunar Hard Lander - 366 kg - (February 17, 1965)
Ranger 9 - USA Lunar HARD Lander - 366 kg - (March 21, 1965)
Luna 5 - USSR Lunar Soft Lander - 1,474 kg - (May 9, 1965) - Failed
Luna 6 - USSR Lunar Soft Lander - 1,440 kg - (June 8, 1965) - Failed
Zond 3 - USSR Lunar Flyby - 959 kg - (July 18, 1965)
Luna 7 - USSR Lunar Soft Lander - 1,504 kg - (October 4, 1965) - Failed
Luna 8 - USSR Lunar Soft Lander - 1,550 kg - (December 3, 1965) - Failed
Luna 9 - USSR Lunar Soft Lander - 1,580 kg - (January 31, 1966) - First lunar lander and first photographs
from the surface
Luna 10 - USSR Lunar Orbiter - 1,597 kg - (March 31, 1966) - First lunar orbiter
Surveyor 1 - USA Lunar Soft Lander - 269 kg - (April 30, 1966 to 1967) - First U.S. soft landing on the Moon
Lunar Exploration – Apollo Era
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Lunar Orbiter 1 - USA Lunar Orbiter - 386 kg - (August 10, 1966)
Luna 11 - USSR Lunar Orbiter - 1,638 kg - (August 24, 1966)
Surveyor 2 - USA Lunar Soft Lander - 292 kg - (September 20, 1966) - Failed
Luna 12 - USSR Lunar Orbiter - 1,620 - (October 22, 1966-1967)
Lunar Orbiter 2 - USA Lunar Orbiter - 390 kg - (November 6, 1966)
Luna 13 - USSR Lunar Soft Lander - 1,700 kg - (December 21, 1966)
Lunar Orbiter 3 - USA Lunar Orbiter - 385 kg - (February 5, 1967)
Surveyor 3 - USA Lunar Soft Lander - 283 kg - (April 17, 1967)
Lunar Orbiter 4 - USA Lunar Orbiter - 390 kg - (May 4, 1967)
Surveyor 4 - USA Lunar Soft Lander - 283 kg - (July 14, 1967)
Explorer 35 - USA Lunar Orbiter - 104 kg - (July 19, 1967 - 1972)
Lunar Orbiter 5 - USA Lunar Orbiter - 389 kg (August 1, 1967)
Surveyor 5 - USA Lunar Soft Lander - 279 kg - (September 8, 1967)
Surveyor 6 - USA Lunar Soft Lander - 280 kg - (November 7, 1967)
Surveyor 7 - USA Lunar Soft Lander - 1,036 kg - (January 7, 1968)
Luna 14 - USSR Lunar Orbiter - 1,700 kg - (April 7, 1968)
Zond 5 - USSR Lunar Flyby - 5,375 kg - (September 14, 1968)
Zond 6 - USSR Flyby - 5,375 - (November 10, 1968)
Apollo 8 - USA Lunar Manned Orbiter - 28,883 kg - (December 21-27, 1968) – First manned mission to the
Moon
Apollo 10 - USA Lunar Manned Orbiter - 42,530 kg - (May 18-26, 1969)
Luna 15 - USSR Lunar Lander - 2,718 kg - (July 13, 1969) - Failed
Apollo 11 - USA Lunar Manned Lander - 43,811 kg - (July 16-24, 1969) – First manned landing on the Moon
Lunar Exploration – Apollo Era
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Zond 7 - USSR Lunar Flyby - 5,979 kg - (August 8, 1969)
Apollo 12 - USA Lunar Manned Lander - 43,848 kg - (November 14-24, 1969)
Apollo 13 - USA Lunar Flyby - 43,924 kg - (April 11-17, 1970)
Luna 16 - USSR Lunar Lander - 5,600 kg - (September 12, 1970) - First USSR
sampled returned from Moon
Zond 8 - USSR Lunar Flyby - (October 20, 1970)
Luna 17 - USSR Lunar Lander and Rover - 5,600 kg - (November 10, 1970 - 1971) –
First lunar rover
Apollo 14 - USA Lunar Manned Lander - 44,456 kg - (January 31 to February 8, 1971)
Apollo 15 - USA Lunar Manned Lander - 46,723 kg - (July 26 to August 7, 1971)
Luna 18 - USSR Lunar Lander - 5,600 kg - (September 2, 1971 - 1972) - Failed
Luna 19 - USSR Lunar Orbiter - 5,600 kg - (September 28, 1971 - 1972)
Luna 20 - USSR Lunar Lander - 5,600 kg - (February 14, 1972) – Sample return
mission
Apollo 16 - USA Manned Lunar Lander - 46,733 kg - (April 16-27, 1972)
Apollo 17 - USA Manned Lunar Lander - 46,743 kg - (December 7-19, 1972)
Luna 21 - USSR Lunar Lander and Rover - 4,850 kg - (January 8, 1973)
Luna 22 - USSR Lunar Orbiter - 5,600 kg - (May 29, 1974 - 1975)
Luna 23 - USSR Lunar Probe - 5,6000 kg - (October 28, 1974) - Failed
Luna 24 - USSR Lunar Lander - 4,800 kg - (August 9, 1976) – Sample return mission
Lunar Exploration – More Recent
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Muses-A (Hiten) - Japan Lunar Orbiters - (January 24, 1990)
- Failed
 Clementine - USA Lunar Orbiter - (January 25, 1994)
 U.S. AsiaSat 3/HGS-1 - Dec 24, 1997 - Lunar flyby
 Lunar Prospector - 295 kg - USA Lunar Orbiter - (January 6,
1998)
 SMART 1 - ESA Lunar Orbiter - 27 September 2003
 Japan Kaguya (SELENE) - Sep 14, 2007 - Lunar orbiter
 China Chang'e 1 - Oct 24, 2007 - Lunar orbiter
 India Chandrayaan-1 - Oct 22, 2008 - Lunar orbiter
 U.S. Lunar Reconnaissance Orbiter and LCROSS - June 17,
2009 - Lunar orbiter and impactor
 China Chang'e 2 - October 2010 - Lunar orbiter
Questions?