Yen-Shan Lim PTYS 395 October 16, 2008

1. Yen-Shan Lim PTYS 395 October 16, 2008

2. 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

3. • 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)

4. 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.

6. 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

7. • Samples of maria (Apollo missions)  basalt • Basalt - dark lava - Iron and magnesium - Very fine (usually <1mm) Lunar lavas  small, bubble-like holes (vesicles)

8. Mare basalt

9. • 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

10. • 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

11. • 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 planet’s interior and slowly migrate upwards - Force their way to the surface - Extruded onto the surface as lava flow

12. 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)

13. • 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

15. • 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.

16. • 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)

17. References Mare Basalt http://images.google.com/imgres?imgurl=http://pds.jpl.nasa.gov/planets/images/browse/earth/basalt.jpg&imgrefurl=http://pds.jpl.nasa.gov/planets/captions/earth/basalt.htm&h=400&w=400&sz=22&hl=en&start=5&usg=__S3ND7NoLEUyrS1PAFy4ox9rrSv0=&tbnid=CYDXdySqeDWDaM:&tbnh=124&tbnw=124&prev=/images%3Fq%3Dbasalt%2Bon%2Bthe%2Bmoon%26gbv%3D2%26hl%3Den%26sa%3DG Tomography of Lunar Spherules http://images.google.com/imgres?imgurl=http://research.amnh.org/~debel/tomo-aps/HI-firefountain1cropLogo.gif&imgrefurl=http://research.amnh.org/~debel/tomo-aps/lunarOG1.html&h=561&w=742&sz=259&hl=en&start=5&usg=__cQ-jFAo0pEWBztXrgYXTajcfWyo=&tbnid=tGw8tTQsv00CuM:&tbnh=107&tbnw=141&prev=/images%3Fq%3Dfire%2Bfountain%2Bon%2Bthe%2Bmoon%26gbv%3D2%26hl%3Den%26sa%3DG

18. Meet the Neighbour http://images.google.com/imgres?imgurl=http://www.spacegazer.com/images/photos/ssmay05moon.jpg&imgrefurl=http://www.spacegazer.com/may-2005-g.asp&h=462&w=480&sz=38&hl=en&start=14&usg=__PAxFKqSz5IAOvDZEAqiK7gdYvDo=&tbnid=EgxDkeyU2ZdlnM:&tbnh=124&tbnw=129&prev=/images%3Fq%3Dmaria%2Bon%2Bthe%2Bmoon%26gbv%3D2%26hl%3Den%26sa%3DG http://images.google.com/imgres?imgurl=http://www.windows.ucar.edu/the_universe/images/maria_5x5.gif&imgrefurl=http://www.windows.ucar.edu/tour/link%3D/earth/images/maria_5x5.html&h=504&w=431&sz=241&hl=en&start=25&usg=__TfcTAraqK5RsXiOiRMcih0gPofc=&tbnid=hlIRS2DcUESmgM:&tbnh=130&tbnw=111&prev=/images%3Fq%3Dmaria%2Bon%2Bthe%2Bmoon%26start%3D18%26gbv%3D2%26ndsp%3D18%26hl%3Den%26sa%3DN Spudis (The Once and Future Moon) Chapter 5