The Concepts of Maria

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Yen-Shan Lim PTYS 395 October 16, 2008
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The Concepts of Maria
Maria dark, smooth, low plains (occupy 16 of
the lunar surface area)
Before space age, concepts for the models of
maria - Dried-up riverbeds - Huge bowls of
dust - Flow of volcanic ash - Melted
material ejected from basin
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The Face of the Moon (1949) Maria were
floods of basalt Basalts sample returned
(4.3 to 3.1 billion years old) - Oldest rocks
on Earth 4.5 billion years old)
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The two basic types of regions on the Moon a
smooth, dark maria on the left and a
heavily-cratered, light-colored highland region
on the upper right.
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Lunar Lava Flows
At close-up scales, small, lobe-shaped scarps
can be seen (common in the lava flows of basalt
found on Earth) Ranger 7 spacecraft returned
close-up pictures of the Moon - Scale of
impact cratering continues downward to the limits
of resolution - Maria are covered by the
regolith Lunar Orbiter spacecraft ?
landforms Surveyors 1, 3, 5 and 6 give a
close-up view of the surface of the maria
dark rocks covered with small holes
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Samples of maria (Apollo missions) ? basalt
Basalt - dark lava - Iron and magnesium
- Very fine (usually lt1mm) Lunar lavas ? small,
bubble-like holes (vesicles)
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Mare basalt
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Lunar lavas - devoid of water - depleted
in all volatile elements (very low bp.) 1st
basalts returned were from Mare Tranquilitatis
? large amounts of titanium Lavas (Moon)
contain minor minerals not found in
Earth rocks ? armalcolite
(another iron
titanium mineral) The viscosity of erupted
lunar lava depends on the composition and
temperature of the magma ? aluminum and
alkali, ? iron, ? temperature at extrusion ?
?viscosity of lavas
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Mare lavas tend to form low, broad structures
volcanoes Lavas from Apollo 12 (formed 3.1
billion years ago) - lower titanium than the
Apollo 11 basalts - 600 to 700 million years
younger - low in volatile elements, very rich
in irons Apollo 15 ? low-titanium basalts,
slightly older than those
from Apollo 12 (3.3 billion years ago)
Apollo 17 ? very high titanium basalts (3.7
billion years old) Conclusion Early eruptions
of high-titanium lavas and late
eruptions of low-titanium lavas
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How lava is formed? - The high density of
mantle is made up of olivine and pyroxene
- Radioactive, heat-producing elements made the
early mantle very hot - Some places are
partially melt - Blobs of melt coagulate deep
in a planets interior and slowly migrate
upwards - Force their way to the surface -
Extruded onto the surface as lava flow
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Fire Fountain
Small glass beads were found in abundance at
Apollo 15 and 17 sites ? clear emerald-green
glass (Apollo 15 site) ? black and orange glass
(Apollo 17 site) The surfaces of these glass
beads have small glassy mounds made up of a
variety of volatile elements (lead, zinc, and
halogens) Apollo 15 glasses (rich in
magnesium, low in titanium) Apollo 17 glass
(rich in titanium)
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The glasses ? products of a spray of
low-viscosity lava into
space Hawaii ? eruptions of lava are
accompanied by very large sprays
of magma from the vent Such spray
eruptions are called fire fountains ? ash
deposit around the eruptive vent Lunar
glasses products of fire fountains on the Moon
over 3 billion years
ago
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Large craters on the Moon have deformed and
fractured floors Along some fractures are small
irregular craters surrounded by a dark,
smooth material These craters ? volcanic vents
surrounded by ash deposits.
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Pockets of gas and other volatile elements
existed deep with the Moon Vesicles are
found in some samples of mare basalt
Composition of this gas phase ? not water
vapor (absence of water-bearing phase) ?
reduced chemistry of lunar lavas (gas
phase might be the carbon monoxide)
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References
Mare Basalt http//images.google.com/imgres?imgurl
http//pds.jpl.nasa.gov/planets/images/browse/ear
th/basalt.jpgimgrefurlhttp//pds.jpl.nasa.gov/pl
anets/captions/earth/basalt.htmh400w400sz22
hlenstart5usg__S3ND7NoLEUyrS1PAFy4ox9rrSv0t
bnidCYDXdySqeDWDaMtbnh124tbnw124prev/image
s3Fq3Dbasalt2Bon2Bthe2Bmoon26gbv3D226hl3D
en26sa3DG Tomography of Lunar
Spherules http//images.google.com/imgres?imgurlh
ttp//research.amnh.org/debel/tomo-aps/HI-firefou
ntain1cropLogo.gifimgrefurlhttp//research.amnh.
org/debel/tomo-aps/lunarOG1.htmlh561w742sz2
59hlenstart5usg__cQ-jFAo0pEWBztXrgYXTajcfWyo
tbnidtGw8tTQsv00CuMtbnh107tbnw141prev/im
ages3Fq3Dfire2Bfountain2Bon2Bthe2Bmoon26gbv
3D226hl3Den26sa3DG
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Meet the Neighbour http//images.google.com/imgres
?imgurlhttp//www.spacegazer.com/images/photos/ss
may05moon.jpgimgrefurlhttp//www.spacegazer.com/
may-2005-g.asph462w480sz38hlenstart14us
g__PAxFKqSz5IAOvDZEAqiK7gdYvDotbnidEgxDkeyU2Zd
lnMtbnh124tbnw129prev/images3Fq3Dmaria2B
on2Bthe2Bmoon26gbv3D226hl3Den26sa3DG http
//images.google.com/imgres?imgurlhttp//www.wind
ows.ucar.edu/the_universe/images/maria_5x5.gifimg
refurlhttp//www.windows.ucar.edu/tour/link3D/ea
rth/images/maria_5x5.htmlh504w431sz241hlen
start25usg__TfcTAraqK5RsXiOiRMcih0gPofctbnid
hlIRS2DcUESmgMtbnh130tbnw111prev/images3F
q3Dmaria2Bon2Bthe2Bmoon26start3D1826gbv3D2
26ndsp3D1826hl3Den26sa3DN Spudis (The
Once and Future Moon) Chapter 5