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1. How are they different?
By the Lunar and Planetary Institute
For use in teacher workshops
Moon Formation / Processes
2. Earth
12,756.3 km diameter
23 degree axis tilt (seasons!)
Surface temps –73 to 48 C
Thick atmosphere, mild
greenhouse effect
Liquid water – lots! - at
surface
3476 km diameter
7 degree tilt (~no seasons)
Surface temps - 107 C to –
153 C
No atmosphere
No liquid water … Ice at
poles in shadows?
Moon
5. A few data to ponder ….
Lower density – “lighter” -
relative to planets
Less iron than whole Earth,
more aluminum and
titanium
Moon’s chemical signature ~
Earth’s mantle
6. 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.
17. Highlands - light,
rough (Terrae)
Mostly anorthosite
(plagioclase feldspars -
lots of calcium and
aluminum)
“In place” rocks are 4.5
to 4.3 billion years old
BIG Dark areas?
Lunar Geologic History
18. Lunar Impact Basins
Imbrium Rim Orientale Basin
Big, frequent impacts until 3.8 billion years ago
Impact events continue on all moons and planets today
24. Lowlands – dark, smooth
Maria (16%)
Basalt – fine grained dark
igneous rock rich in iron
and magnesium (stuff
that sank in magma
ocean)
Few hundred meters thick
Ro cks are 4.3 to 3.1 billion
years old … volcanic
flows as recently as 1
billion years ago!!
Lunar Geologic History
29. How are they different in terms of
geologic processes?
And WHY?
30. Earth
Active wind/water erosion
Impacts
Active volcanoes
Earthquakes
Active magnetic field
Few craters
Geologically Active!
Moon
NO Active wind/water erosion
Impacts
NO active volcanoes
Small moonquakes
NO active magnetic field
Buckets of craters
Geologically Inactive!
33. What’s Our Plan for Space?
• Fly the shuttle as safely as
possible until 2010
• Complete the ISS – 6-person
crew by 2009
• Align science, exploration, and
aeronautics to support human
space flight
• Bring the new Crew
Exploration Vehicle – CEV -
on line
• Establish a lunar program that
informs future missions to
Mars and other destinations
34. Why?
• Set up, for the first time, a full-fledged habitat on
another world.
• Test advanced spacesuits and rovers.
• Try out methods for protecting explorers from deadly
radiation.
• Learn to operate crucial life support and power
needed on Mars.
• Gauge the effects of the absence of normal gravity
on the body.
• New technology.
35. Return to the Moon
Chandryaan – 2007!
LRO – 2008 !
Identify Resources
Map the Surface
36. Return to the Moon!
• 2012 – Develop and test
technologies for resource
utilization, communications,
power
• 2014 – CEV, Ares launch
vehicle
37. • 2018 – Humans for week-long stays
• Next: 45-day stays at outposts
Notes de l'éditeur
The Earth-Moon SystemDate: 12.16.1992Eight days after its final encounter with the Earth, the Galileo spacecraft looked back and captured this remarkable view of the Earth and Moon. The image was taken from a distance of about 6.2 million kilometers (3.9 million miles). The picture was constructed from images taken through the violet, red, and 1.0-micron infrared filters. The Moon is in the foreground, moving from left to right. The brightly-colored Earth contrasts strongly with the Moon, which reflects only about one-third as much sunlight as the Earth. Contrast and color have been computer-enhanced for both objects to improve visibility. Antarctica is visible through clouds (bottom). The Moon's far side is seen; the shadowy indentation in the dawn terminator is the south pole Aitken Basin, one of the largest and oldest lunar impact features. Image Credit: NASA
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=1879
A cross section view of the Moon’s internal structure. The outer, rocky crust averages about 60 km thick. Most of the Moon is the mantle, which is also rocky but of somewhat different composition than the crust (more magnesium, less iron and aluminum). There is probably also a small, iron rich core, a few hundred km in size at the center of the Moon.
http://photojournal.jpl.nasa.gov/catalog/PIA00094
http://photojournal.jpl.nasa.gov/catalog/PIA00405
The moon is enriched in Titanium, Aluminum, and related elements and depleted in iron and volatile elements (and compounds - DRY!)
The moon (~3.3) has a low density compared to earth (~5.5)
Earth/moon has anomalously large amount of angular momentum compared to other planets - conservation of momentum. Angular momentum is the measure of rotation in a system.
The combined momentum of these two closely related bodies must stay the same over time. If moon closer earlier, then earth must have been rotating faster (shorter days).
Momentum = mass x velocity
Angular momentum = mass x velocity in a circle
Earth’s high because earth + moon + impact = higher momentum
Old highlands (cratered), young basalt “seas”. 4.5 billion years ago.
Formation of the Moons's geosphere
(fig p179 McSween) The moon too developed a magma ocean during its formation due to the same sources of heat, impact, internal compression, radiogenic decay and gravitational tides. We know this because when the first moon rocks were brought back to Earth during the Apollo program they were composed almost entirely of one mineral -- Feldspar. The only way to form such a rock (called Anorthosite) is to precipitate crystals from a molten lava and then separate the cystals according to differences in density -- a process known as fractional crystallization. This would happen if feldspar crystals intially crystallized with other minerals but then floated to the surface of a large magma ocean. The denser minerals would sink and the less dense minerals would float. Eventually, when the magma ocean cooled and solidified the crustal surface would be dominated by feldspar and the rock would be Anorthosite. This separating out of minerals of different density is known to occur in magma chambers within the continetal crust on Earth, but the planetary scale of this process on the moon is mind-boggling.
(fig p178 Mc Sween) Estimates of the thickness of the Anothosite crustal layer on the moon indicate that it is ~20 km thick. To separate out a 20 km thick layer of feldspar from a molten magma requires a magma ocean that was at least 1000 km thick. So far measurement of radiometric ages of the Anorthosites indicates that the lunar crust solidified 4400 Ma ago, only 200 Ma after the formation of the solar system.
http://www.psi.edu/projects/moon/moon.html
The moon is a sister world that formed in orbit around Earth as the Earth formed. This theory failed because it could not explain why the moon lacks iron.
A second early idea was that the moon formed somewhere else in the solar system where there was little iron, and then was captured into orbit around Earth. This failed when lunar rocks showed the same isotope composition as the Earth.
A third early idea was that early Earth spun so fast that it spun off the moon. This idea would produce a moon similar to Earth's mantle, but it failed when analysis of the total angular momentum and energy involved indicated that the present Earth-moon system could not form in this way.
These were the three main models for the formation of the Moon at the time of the Apollo program. It turns out that each fails to explain some major observation about the Moon. For more about these models, see the Scientific American article by Jeff Taylor cited in the notes for slide 2. Artwork is from Taylor’s article.
Fission – 10 hour rotation worked out for E + M … to spin Moon off would have to be rotating every 4 hours
1) Moon / Earth accreted as two-planet system.
Problem: Dissimilar compositions.
2) Moon accreted separately, captured by Earth.
Problem: mechanics of orbital capture.
3) Moon spun off from Earth during Earth’s differentiation. Pacific Ocean is hole left by Moon.
Problem: Moon could not reach escape velocity.
Okay and the Pacific thing doesn’t work on fist blush - plate tectonics ...
4) Impact by a Mars-sized protoplanet bounced Moon off Earth (after Earth’s core partially formed.
Explains difference in composition, relative sizes.
http://www.psi.edu/projects/moon/moon.html
http://photojournal.jpl.nasa.gov/catalog/PIA00405
Of course, history is more complex
Lunar highland rocks can be divided into those that are slightly iron rich (formed soon after Moon formed – oldest is 4.5 billion years) and those that are magnesium rich and range in age from 4.5 to 4.3 – indicates different magma sources
Cooled by about 4.3 – KREEP rocks – consistent in mineralogy but scattered across highlands (potassium, rare earth elements, phosphorous)
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.
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.
The lunar magma ocean cooled and crystallized, forming a crust about 60 kilometers thick. Asteroids continued to bombard the Moon, leaving impact craters.
Photo Credits: NASA
http://www.nasm.si.edu/exhibitions/cchoice/moonrocks/moonrocks6.htm
http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html
http://curator.jsc.nasa.gov/lunar/compendium.cfm
These are two examples of rocks that crystallized from the lunar magma ocean. Both are made primarily of the mineral plagioclase, which gives the lunar highlands its light gray color. The troctolite also contains some greenish olivine grains (troctolite may be later intrusion).
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.
http://photojournal.jpl.nasa.gov/catalog/PIA00405
Of course, history is more complex
Lunar highland rocks can be divided into those that are slightly iron rich (formed soon after Moon formed – oldest is 4.5 billion years) and those that are magnesium rich and range in age from 4.5 to 4.3 – indicates different magma sources
Cooled by about 4.3 – KREEP rocks – consistent in mineralogy but scattered across highlands (potassium, rare earth elements, phosphorous)
NASA/LPI
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.
http://photojournal.jpl.nasa.gov/catalog/PIA00405
NASA / LPI
This image clearly shows both the central peak and terracing in the walls of Tycho. Tycho is in the lunar highlands, and the terrain surrounding the crater is quite rugged. The crater floor is also fairly hummocky. Multispectral images obtained by the Clementine spacecraft show that the central peak has a different composition than the surrounding material, presumably because the central peak is composed of material that originated at greater depths in the Moon's crust. (Lunar Orbiter image V-125M.)
Tycho Crater
Tycho Crater, about 85 kilometers across, is clearly visible on our Moon’s surface. The freshness of the crater and the rays of material radiating from it suggest that this is a young crater; there has been little time to erode it.
100 Ma
Clementine - http://antwrp.gsfc.nasa.gov/apod/ap961204.html
Equatorial escape velocity – 2.4 km/s vs 11.2 km/s on Earth
http://www.lpi.usra.edu/expmoon/Apollo15/A15_ImpMeltFS.gif
http://curator.jsc.nasa.gov/lunar/compendium.cfm
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.)
NASA / LPI
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)
Moon Becomes Geologically Inactive
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. 3.0 Ga
http://hvo.wr.usgs.gov/gallery/kilauea/erupt/24ds182_caption.html
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)
Moon Becomes Geologically Inactive
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. 3.0 Ga
Fissure eruption -- Fissure eruption generating a "curtain of fire" on the Kilauea volcano, Hawaii in 1992. The Pu'u O'o volcano is located just beyond the photograph to the lower left. Courtesy of USGS.
http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/Puuoorift_page.html
NASA / LPI
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.
http://curator.jsc.nasa.gov/lunar/compendium.cfm
http://curator.jsc.nasa.gov/lunar/compendium.cfm
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.
http://photojournal.jpl.nasa.gov/catalog/PIA00405
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.
http://science.nasa.gov/headlines/y2005/22dec_lunartaurid.htm
The blast was equal in energy to about 70kg of TNT and was seen near the edge of Mare Imbrium (the Sea of Rains).
The object that hit the Moon was probably part of a shower of "taurids" which peppered Earth in late October and early November.
Understanding lunar impacts could help protect astronauts when Nasa sends humans back to the Moon.
Meteoroids are small rocky or metallic objects in orbit around the Sun, or another star. One of the astronomers who observed the impact estimates that it gouged a crater 3m wide and 0.4m deep.
Rob Suggs of Nasa's Marshall Space Flight Center in Huntsville, US, was testing a new 10-in telescope and video camera assembled to monitor the Moon for space strikes.
On 7 November, his first night using the telescope, he observed one.
Renewed interest
"People just do not look at the Moon anymore," said Dr Suggs, of Marshall's engineering directorate.
"We tend to think of it as a known quantity; but there is knowledge still to be gained here."
Dr Suggs used commercial software to study the video he took, and spotted a very bright flash. The burst of light diminished gradually over the course of five video frames, each 1/30th of a second in duration.
The explosion can be seen in these video framesHe and Nasa astronomer Bill Cooke consulted star charts and lunar imaging software, and determined the meteoroid was probably a taurid, part of an annual meteor shower active at the time of the strike.
Like Earth, the Moon was peppered by taurids in late October and early November.
But unlike our planet, the Moon has no atmosphere to intercept and vaporise them, so they explode on the surface.
Since the Leonids of 2001, astronomers have not spent much time hunting for lunar impacts.
However, as Nasa plans to return to the Moon by 2020, the agency says it needs to understand what happens after lunar impacts in order to protect astronauts.
Dr Suggs said planetary scientists wanted to know how often big meteoroids hit the Moon and whether they only happened during showers like the taurids or were a more common occurrence.
Bill Cooke said that while the odds of a direct hit with a big meteoroid were almost nil for an individual astronaut, they might be shorter for an entire lunar outpost.
www.nps.gov/grsa/ resources/photos_dunes.htm
http://www.nps.gov/grca/photos/index.htm
Public Domain
The Earth-Moon SystemDate: 12.16.1992Eight days after its final encounter with the Earth, the Galileo spacecraft looked back and captured this remarkable view of the Earth and Moon. The image was taken from a distance of about 6.2 million kilometers (3.9 million miles). The picture was constructed from images taken through the violet, red, and 1.0-micron infrared filters. The Moon is in the foreground, moving from left to right. The brightly-colored Earth contrasts strongly with the Moon, which reflects only about one-third as much sunlight as the Earth. Contrast and color have been computer-enhanced for both objects to improve visibility. Antarctica is visible through clouds (bottom). The Moon's far side is seen; the shadowy indentation in the dawn terminator is the south pole Aitken Basin, one of the largest and oldest lunar impact features. Image Credit: NASA
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=1879
http://photojournal.jpl.nasa.gov/catalog/PIA00405
http://lunar.gsfc.nasa.gov/gallery/index.html
NASA Clementine
LRO - More / more detailed data: temperature, radiation, distribution of hydrogen (=water), ice, other elements, characterization of surface topography to 0.5 m, properties of lunar soil
http://www.nasa.gov/images/content/156337main_Orion_with_LSAM.jpg - Orion docked with a lunar lander in orbit around the moon. Photo credit: Lockheed Martin Corp.
http://www.space.com/news/050914_nasa_cev_update.html
WASHINGTON – NASA briefed senior White House officials Wednesday on its plan to spend $100 billion and the next 12 years building the spacecraft and rockets it needs to put humans back on the Moon by 2018.
The U.S. space agency now expects to roll out its lunar exploration plan to key Congressional committees on Friday and to the broader public through a news conference on Monday, Washington sources tell SPACE.com.
U.S. President George W. Bush called in January 2004 for the United States to return to the Moon by 2020 as the first major step in a broader space exploration vision aimed at extending the human presence throughout the solar system.
NASA has been working intensely since April on an exploration plan that entails building an 18-foot (5.5-meter) blunt body crew capsule and launchers built from major space shuttle components including the main engines, solid rocket boosters and massive external fuel tanks.
That plan, called the Exploration Systems Architecture Study, was presented by NASA Administrator Mike Griffin, his space operations chief Bill Gerstenmaier and several other senior agency officials Wednesday afternoon to senior White House policy officials, including an advisor to U.S. Vice President Richard Cheney and the president’s Deputy National Security Advisor J.D. Crouch.
NASA’s plan, according to briefing charts obtained by SPACE.com, envisions beginning a sustained lunar exploration campaign in 2018 by landing four astronauts on the Moon for a seven-day stay.
The expedition would begin, these charts show, by launching the lunar lander and Earth departure stage (essentially a giant propulsion module) on a heavy-lift launch vehicle that would be lifted into orbit by five space shuttle main engines and a pair of five-segment shuttle solid rocket boosters.
Once the Earth departure stage and lunar lander are safely in orbit, NASA would launch the Crew Exploration Vehicle capsule atop a new launcher built from a four-segment shuttle solid rocket booster and an upper stage powered by a single space shuttle main engine.
The CEV would then dock with the lunar lander and Earth departure stage and begin its several day journey to the Moon.
NASA’s plan envisions being able to land four-person human crews anywhere on the Moon’s surface and to eventually use the system to transport crew members to and from a lunar outpost that it would consider building on the lunar south pole, according to the charts, because of the regions elevated quantities of hydrogen and possibly water ice.
One of NASA’s reasons for going back to the Moon is to demonstrate that astronauts can essentially “live off the land” by using lunar resources to produce potable water, fuel and other valuable commodities. Such capabilities are considered extremely important to human expeditions to Mars which, because of the distances involved, would be much longer missions entailing a minimum of 500 days spent on the planet’s surface.
NASA’s Crew Exploration Vehicle is expected to cost $5.5 billion to develop, according to government and industry sources, and the Crew Launch Vehicle another $4.5 billion. The heavy-lift launcher, which would be capable of lofting 125 metric tons of payload, is expected to cost more than $5 billion but less than $10 billion to develop, according to these sources.
NASA’s plan also calls for using the Crew Exploration Vehicle, equipped with as many as six seats, to transport astronauts to and from the international space station. An unmanned version of the Crew Exploration Vehicle could be used to deliver a limited amount of cargo to the space station.
NASA would like to field the Crew Exploration Vehicle by 2011, or within a year of when it plans to fly the space shuttle for the last time. Development of the heavy lift launcher, lunar lander and Earth departure stage would begin in 2011. By that time, according to NASA’s charts, the space agency would expect to be spending $7 billion a year on its exploration efforts, a figure projected to grow to more than $15 billion a year by 2018, that date NASA has targeted for its first human lunar landing since Apollo 17 in 1972.
http://www.nasa.gov/mission_pages/exploration/main/index.html
http://www.nasa.gov/mission_pages/exploration/multimedia/vision_images_search_agent_archive_1.html
Set up, for the first time, a full-fledged habitat on another world. Test advanced spacesuits and rovers. Try out methods for protecting explorers from deadly radiation. Learn to operate crucial life support and power needed on Mars. Gauge the effects of the absence of normal gravity on the body.
http://photojournal.jpl.nasa.gov/catalog/PIA00405
Original Caption Released with Image:
During its flight, the Galileo spacecraft returned images of the Moon. The Galileo spacecraft took these images on December 7, 1992 on its way to explore the Jupiter system in 1995-97. The distinct bright ray crater at the bottom of the image is the Tycho impact basin. The dark areas are lava rock filled impact basins: Oceanus Procellarum (on the left), Mare Imbrium (center left), Mare Serenitatis and Mare Tranquillitatis (center), and Mare Crisium (near the right edge). This picture contains images through the Violet, 756 nm, 968 nm filters. The color is 'enhanced' in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision. The Galileo project is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory.
