Presentation on theme: "Moon rocks, dust and lunar meteorites Key Features of the Moon: pages 156 - 164 and 172 - 192."— Presentation transcript:
Moon rocks, dust and lunar meteorites Key Features of the Moon: pages 156 - 164 and 172 - 192
Physical parameters for the Moon * * * * * 1/6 th the Earth’s
Why study the Moon? The Moon is ancient and preserves an early history (the first billion years) that is common to all terrestrial planets. Active geologic forces, including plate tectonics and erosion, continuously destroy the oldest surfaces on Earth, whereas old surfaces persist with little disturbance on the Moon. Provides a key for unraveling time scales for the geologic evolution of Mercury, Venus, and Mars based on their individual crater records. Photogeologic interpretation of other planets is based largely on lessons learned from the Moon.
The Moon’s face The highlands (terra) are brighter and have more craters than maria (pl: mare). What caused these differences?
The astronaut’s footprint in the lunar soil (regolith) will last for millions of years, until wiped out by impacts of meteoroids from space.
This lunar soil, recovered by Apollo 11 from Mare Tranquillitatis, was cleaned with acetone to remove ultra- fine dust. It consists of impact-produced glass spheres < 1 mm in diameter, brown pyroxene (an Fe,Mg silicate), white anorthite (a calcium-aluminum silicate), and various rock fragments.
Mare basalts Maria –Dark –Low in aluminum –High in iron –Poor in plagioclase –High in pyroxene & olivine –Exhibit younger isotopic dates (4.1- 3.1 Ga) –Have fewer craters
Thin section photomicrograph in transmitted polarized light of an Apollo 15 fine-grained pyroxene-phyric mare basalt
Thin section photomicrograph in transmitted polarized light of an Apollo 15 Medium-grained pyroxene-phyric mare basalt
Thin section photomicrograph in transmitted polarized light of an Apollo 15 Coarse-grained pyroxene-phyric mare basalt
Explosive volcanism: Fire fountaining at Pu’u O’o, Hawaii, on June 2, 1986.
The famous “orange soil” glass spheres from the Apollo 17 landing site. They are thought to have formed by explosive volcanism (fire fountaining). The spheres are < 1mm in size.
The first lunar meteorite ever recovered on Earth!
Thin section photograph of the first lunar meteorite recovered on Earth, ALHA 81005, a lunar regolith breccia (~ 2mm in diameter).
For comparison, this is a photograph of an Apollo 14 regolith breccia, which clearly shows the similarity in texture to the lunar meteorite, ALHA 81005.
The abundances of certain chemical elements (here La and K) in rocks are “finger prints” for their origin on a particular planet. Shergottites, nakhlites, chassignites = Mars; Eucrites, howardites = asteroid Vesta. ALHA 81005 clearly plots with analyses of Apollo Moon rocks!!!
The value of the ~ 30 known lunar meteorites is that they, most likely, do not come from the sites were the Apollo missions landed. Thus, they provide us with rocks from new, previously not visited sites on the Moon.
Ice at the Poles 60 - 70% 20 - 30% 1 - 10% 50 - 60% % time in shadows at S. Pole region