1. Lunar Evolution: A “Life Story” View of the Moon
Andrea Jones
Lunar and Planetary Institute
NASA Goddard Space Flight Center

2. Happy Birthday, Moon! 4.5 billion years ago, our Moon forms
(lunar rocks and meteorites)
Copyrighted, LPI, Leanne Woolley

3. Impact by Mars-sized proto-planet
4.5 billion years ago
Explains:
Chemistry
Orbit
Large angular momentum
This leads us to…
Impact by a Mars-sized protoplanet after Earth’s core partially formed.
Explains difference in composition, orbit, relative sizes, large angular momentum.
Hartman and Davis, 1975

4. Moon Formation Video Note – Not from NASA
But, it gets the main points across
Moon Formation Video

5. Infant Moon: The Magma Ocean
The energy from the Moon’s initial formation caused at least the outer few hundred kilometers of material to melt. This is known as the magma ocean stage, literally a deep ocean of molten rock. This solidified during the first 50 to 100 million years of lunar history, roughly 12:30 am on our 24 hour clock. Artwork is from the Jeff Taylor article cited in slide 2 [of Shipp’s presentation].
This diagram depicts the magma ocean concept. When the Moon formed it was enveloped by a layer of molten rock (magma) hundreds of kilometers thick. As that magma crystallized, the minerals more dense than the magma sank while those less dense (such as feldspar) floated, forming the anorthosite crust. The dense minerals (olivine and pyroxene) later remelted to produce the basalts that compose the maria. (Graphics by Brooks Bays, University of Hawaii.)
The lunar magma ocean cooled and crystallized, forming a crust ~70 kilometers (~40 miles) thick. Asteroids continued to bombard the Moon, leaving impact craters.
Differentiation!

6. Infant Moon: The Magma Ocean

7. Infant Moon Rocks: Primarily Anorthosites
60025
Anorthosite Ga
Oldest
rocks
on Moon
from
this time
Rock that crystallized from the lunar magma ocean. Made primarily of the mineral plagioclase, which gives the lunar highlands its light gray color. The lunar highlands are made primarily of a single mineral: low-density, aluminum-rich, plagioclase feldspar. This mineral floated to the top of the magma ocean and crystallized to form the light-colored rock anorthosite.
Plagioclase feldspar
Does not form if water is present
Single mineral – indicates it separated in a magma
This is a sample of anorthosite returned by the Apollo 15 mission. Anorthosites are composed almost entirely of one mineral, plagioclase feldspar. One way a single-mineral rock forms is by accumulation by either floating or sinking in a magma. Because anorthosite seems to be an abundant and widespread rock type in the lunar highlands, scientists believe that the Moon was surrounded completely by a huge ocean of magma soon after it formed.
Anorthosite is a coarse-grained igneous rock made largely of plagioclase feldspar (95%), with small amounts of pyroxene (4%), olivine, and iron oxides. Anorthosite makes up about 60% of Earth's crust. It was found in all the rocks returned from the Moon, including the oldest (dating back 4.4 to 4.5 billion years), and is believed to make up a significant fraction of the lunar crust. Anorthite is an end member and one of the rarer members of the plagioclase series. The plagioclase series comprises minerals that range in chemical composition from pure NaAlSi3 O8, Albite to pure CaAl2 Si2 O8 , anorthite. Anorthite by definition must contain no more than 10% sodium and no less than 90% calcium in the sodium/calcium position in the crystal structure. The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements.

8. Infant Moon Produced Light Areas: The Lunar Highlands
Light, rough
Mostly anorthosite
(plagioclase feldspars - lots of calcium and aluminum)
“In place” rocks: 4.5 to 4.3 billion years old

9. Kid Moon: Big Impacts Form Big Basins
Big, frequent impacts until 3.8 billion years ago
Peak at/until 3.9 billion years ago: The Late Heavy Bombardment
Impact events continue on all moons and planets today
Both Earth and Moon were struck by numerous large asteroids and comets in their early history. These impacts produced deep basins up to 1000 km across surrounded by high rings of mountains on the Moon and are visible to the human eye as prominent circular structures. Left: A view of the mountains that surround the Imbrium impact basin. The smooth, dark region on the right side of the image is younger lava flows. Right: Three mountain rings surround the Orientale impact basin. Both the Imbrium and the Orientale impacts occurred around 3.8 billion years ago, roughly 4 am on our 24 hour clock.
Largest impact basin from this time: South Pole Aitken Basin - ~2500 km (~1500 miles) in diameter and ~13 km (~8 miles) deep.
Orientale Basin
LROC WAC mosaic, Orientale Basin

10. Formation of a Complex Crater

11. Kid Moon Rocks: Breccias and Impact Melts
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Impact melt + clasts
The force of such large impacts can fragment the original lunar rocks and compress them into new, complex rocks known as breccias. Sometimes, portions of the rock melt and resolidify, which allows the age of the impact to be measured using radiometric dating methods (i.e., from the decay of radioactive parent elements into stable daughter elements. The amount of parent decreases with age and the amount of daughter increases with age.)
67016
Polymict Breccia

12. Teen Moon: Lunar Volcanism Produced the Dark Areas: Mare
Mare volcanism after impacts –
Most before 3 billion years ago
Minor volcanism continued until ~1 billion years ago
The deep parts of many large impact basins were later filled by eruptions of basaltic lava. This forms the circular Mare Imbrium (left image). At right, shadows reveal the edges of a long lava flow from the lower left to the upper right of the image. The volcanism in Mare Imbrium occurred about 3.3 billion years ago (7 am on our clock). Because of its small size, the Moon cooled quickly and was mostly dead volcanically by 3 billion years ago, although limited volcanism in isolated regions is thought to have occurred as recently as 1 to 2 billion years ago.
Lunar Volcanism
Portions of the Moon’s interior remained hot enough to produce magma for more than a billion years after it formed. Molten rock flowed onto the lunar surface through cracks in the crust, spreading out and filling the low regions in the impact basins. The lava cooled quickly, forming the fine-grained, dark rocks — basalt — sampled during the Apollo missions. The dark areas seen on the Moon are basaltic lava plains 4.2 to 1 billion
(place at 3.5) Lunar volcanism decreased significantly by 3 billion years ago and ceased completely by about 1 billion years ago as the interior of this small body cooled Ga
While cool on the outside, portions of the lunar interior were still hot, heated by radioactive decay of unstable isotopes of elements, such as uranium and thorium, and the processes of accretion and differentiation.
Mare Imbrium

13. Fissure Eruptions Model Example from Hawaii
Heat to melt the mantle rock came from radioactive decay of elements. Basins are areas where crust is thinned and fractured by impact – logical places for magma to work its way into….. And they are low – liquids fill low areas
Lunar Volcanism
Portions of the Moon’s interior remained hot enough to produce magma for more than a billion years after it formed. Molten rock flowed onto the lunar surface through cracks in the crust, spreading out and filling the low regions in the impact basins. The lava cooled quickly, forming the fine-grained, dark rocks — basalt — sampled during the Apollo missions. The dark areas seen on the Moon are basaltic lava plains 4.2 to 1 billion (place at 3.5)
Fissure eruption -- Fissure eruption generating a "curtain of fire" on the Kilauea volcano, Hawaii in The Pu'u O'o volcano is located just beyond the photograph to the lower left. Courtesy of USGS.
Model
Example from Hawaii

14. Other Examples of Lunar Volcanism
Rare volcanic domes
Rilles – lava channels
Volcanism finished by 1 billion years ago
These images from orbit around the Moon illustrate some other areas produced by volcanism. Both would be interesting areas for future exploration.
Although eruption of most mare basalts did not produce volcanic mountains, there are a small volcanic domes in a few places. This shows the Marius Hills, a collection of relatively low domes. Rilles (sinuous lava channels) are also visible, one of which cuts across a mare ridge. (Lunar Orbiter V-214-M)
11. Marius Hills, Moon
Although most lunar volcanism produced the broad lava flows that infill the lunar maria, in a few places, such as the Marius Hills (14°N, 56°W), it is possible to find volcanic domes. In this scene we can see several lunar domes. Some of these domes are quite smooth and low, while others are more rugged and heavily cratered. Two large sinuous rilles similar to Hadley Rille (slide #12) can also be seen cross-cutting a mare ridge.
Aristarchus Plateau
Marius Hills

15. Teen Moon Rocks: Lunar Basalts
15555
3.3 billion
years old
15016
These rocks are typical of lunar volcanic rocks. Collected on Apollo 15, both are 3.3 billion year old basalts, similar to those produced by volcanos such as Hawaii on Earth. The lower image (sample 15016) contained some type of gas, possibly carbon monoxide, which formed the round holes known as vesicles.
Younger than
rocks found in
lunar highlands

16. Teen Moon Produced Dark Areas: The Lunar Maria
Dark, smooth
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 … flows as recently as 1 billion years ago
Basalts also unusually high in titanium – 10x more than on Earth
Basalts on Moon formed in mantle – devoid of water – no hydrated minerals
Lots of volcanic glass beads – fire fountains of Hawaii – magma spewed into space and cooled immediately before any crystalline structure could form.

17. Adult Moon: The Moon We See Today
Period of ongoing impacts, human and robotic exploration
Layer of fine, dusty regolith accumulating
No atmosphere, water, or life to disturb surface
Footprints of 12 astronauts who visited the Moon between will be preserved for a long time!
Basalts also unusually high in titanium – 10x more than on Earth
Basalts on Moon formed in mantle – devoid of water – no hydrated minerals
Lots of volcanic glass beads – fire fountains of Hawaii – magma spewed into space and cooled immediately before any crystalline structure could form.

18. Evolution of the Moon Video
From NASA
Moon Evolution Video

19. Current Mission: The Lunar Reconnaissance Orbiter
Diviner (top L), LOLA (bottom L), and LROC (bottom R)