Lunar Rocks Lunar Interior Lunar Structure Lunar Formation Lunar Chronology Lunar Geology Lunar Exploration.

•Lunar Rocks•Lunar Interior•Lunar Structure•Lunar Formation•Lunar Chronology•Lunar Geology•Lunar Exploration

Lunar RocksLunar Rocks

Lunar Rocks

Basic classification Elements - individual

atom species that are the basic building blocks of ordinary matter

Minerals - are composed of elements or compounds of the elements, and are often designated by the most common atoms/molecules contained in that mineral

Rocks - composed of combinations of minerals/elements and can be classified into three major types on Earth: sedimentary, metamorphic and igneous

Lunar Rocks

Because the Moon is small and there is no atmosphere, water is missing from the compounds that make up lunar rocks

Sedimentary rocks are also not found on the Moon because there is no water or wind

There are similarities in the lunar rocks and those found on Earth, including metal oxides, silicates, as well as some carbonaceous rocks

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

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

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

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

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

Basalt forms when magma flows onto the surface of the Moon, cools and then crystallizes

Basalt lava flows are the dark materials that have filled the lowlands on the Moon's surface which cover about one-quarter the Moon's surface area

The basalt flows are generally 3.1 to 3.8 billion years (Gigayears, or Gy) old

Lunar Rocks

Breccia

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

Fragments heated by the collisions that broke them apart melted and stuck to other grains composed of broken rocks and smaller mineral grains

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

Anorthosite, also found in abundance on Earth, is a light-colored rock composed mostly of crystals of the mineral feldspar - primarily silicates

Anorthosite rocks make up much of the highlands of the Moon, with the feldspars producing the light color

The first feldspar crystals were pale gray or colorless and later broken into fragments; the resulting shattered feldspar crystals produced the whitish color

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 StructureLunar Structure

Lunar Stats

Mass 7.349x1022 kg (1/81 MEarth) Radius 1,738 km (equatorial) (0.27 REarth) Mean density 3.35 g/cm3

Orbital eccentricity 0.055 Orbit inclination 5.14o (from Earth's equator) Semimajor axis 384,400 km Orbit period 29.5 days solar (27.3 days sidereal) Rotation period 29.5 days Magnetic field <0.0001 Gauss Albedo 0.12 Atmosphere 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

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

The Moon's original plagioclase crust identified as highlands because of its generally higher elevation experienced an intrusion of slightly heavier magnesium-rich magma that contained less plagioclase and more olivene and pyroxene

Lunar Highlands

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

Crust formation ended 4.1 billion years ago when the upper-mantle solidified

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

Heavy bombardment of the lunar surface continued until approximately 3.9 billion years ago

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

As planetesimal impacts began to wane, the insulation properties of the thickening crust and continuing radioactivity decay began heating the interior

Lunar Maria

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

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

These vast areas called maria, or seas, have distinctly different geological appearance and composition

Lunar Maria

The most distinctive difference is the dark, smooth surface of the mare compared to the rough highlands

Because the impacts declined in size and number, the younger lunar mare show fewer large craters than the highlands

Lunar FormationLunar Formation

Lunar Surface Composition

Anorthocite, which is predominantly aluminum-calcium silicates, offers a greater abundance of both calcium and aluminum than in the Earth's crust

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)

Basalt is composed of a broad combination of silicate and oxide minerals that are rich in magnesium, iron and titanium

These minerals are commonly metal oxides (MgO, TiO, FeO), combined with silica

Lunar Surface Composition

One of the more common metal oxide silica minerals in the lunar basalts is olivene, which is a combination of magnesium oxide plus silica

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

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

The magnetized surface rock indicates a very small but measurable lunar magnetic field at various times during the crustal rock formation

Slight magnetization also appears in the highlands, possibly due to impact shock

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)

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 The Four Basic Theories of Lunar FormationFormation

1. Capture1. Capture2. Coaccretion2. Coaccretion3. Fission3. Fission4. Collision4. 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)

Attractive because of its simplicity

Easily dismissed because of the different composition abundance of Earth and Moon (especially iron)

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

Attractive because of simplicity and the lack of a unique, catastrophic event

Highly improbable because the actual composition differences between Earth and the Moon are not accounted for

Not possible, or certainly improbable, because the orbital angular momentum is too small for this mechanism when compared to the Earth-Moon angular momentum

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 semi-liquid 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

Attractive because it can explain composition differences in the Earth and the Moon

Validation of a fissioning planet is difficult to model numerically

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

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.)

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

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

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

Lunar Geology

Regolith

Regolith is the broken rock and dust layer that covers the entire Moon, arising from repeated impacts over its lifetime

This layer covers entire surface to a  depth of several cm to 100 m

Churned by micrometeoroids over billions of years exposing subsurface material

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: – 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

Commonly represent crater ridges

Formed also from  fractures and faulting as Moon shrank

Lunar Geology

Valleys  (rills)

Valleys can form from several mechanisms:

Lava channel shrinking after its flow subsides

Fracture lines from crust shrinking

Relatively narrow and long

Lunar Geology

Volcanic outflow

Seas (Mare - Latin for seas) – Cover 17% of lunar surface– Thick crust slows flow– Some small cone volcano

formations are seen on the Moon

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

Distinctly different geology since the lunar core was displaced toward Earth due to synchronous rotation

Thinner crust on the near side (facing Earth) had far more mare than the far side of the Moon

Lunar Exploration Lunar Exploration

Lunar Exploration - Early

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

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

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

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 flybyU.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 orbiterJapan Kaguya (SELENE) - Sep 14, 2007 - Lunar orbiter China Chang'e 1 - Oct 24, 2007 - Lunar orbiterChina Chang'e 1 - Oct 24, 2007 - Lunar orbiter India Chandrayaan-1 - Oct 22, 2008 - Lunar orbiterIndia Chandrayaan-1 - Oct 22, 2008 - Lunar orbiter U.S. Lunar Reconnaissance Orbiter and LCROSS - June 17, U.S. Lunar Reconnaissance Orbiter and LCROSS - June 17,

2009 - Lunar orbiter and impactor2009 - Lunar orbiter and impactor China Chang'e 2 - October 2010 - Lunar orbiterChina Chang'e 2 - October 2010 - Lunar orbiter

Questions?Questions?