Moon rocks, dust and lunar meteorites Key Features of the Moon: pages and

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?

Topography of the Moon S. Pole/Aitkin Basin

The types of soil and rock on the Moon

Mare soil (regolith)

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 ( 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.

Thin section photomicrograph in polarized light of a crystallized sphere of the famous “green glass” that is also thought to have formed by explosive volcanism (fire fountaining).

Highlands Crust Highlands –Bright –High in aluminum –Low in iron –Rich in plagioclase –Low in pyroxene & olivine –Exhibit old isotopic dates ( Ga) –Have lots of craters

A highlands breccia from the Apollo 16 landing site, consisting of comminuted anorthositic rocks.

Photomicrograph in transmitted light of one of the few unadulterated, pristine igneous rocks from the lunar highlands, a spinel troctolite.

Photomicrograph in transmitted polarized light of one of the few unadulterated, pristine igneous rocks from the lunar highlands, a spinel troctolite.

Search on the “blue ice” of Antarctica for meteorites, including those ejected by impacts from the Moon

Discovery on the “blue ice” of Antarctica of large numbers of meteorites, including some ejected by impacts from the Moon.

Antarctica is the best place to find meteorites on Earth, because the ice preserves them for 10 6 years, and because the movement of ice concentrates meteorites in areas of blue ice!

Flow of ice from center of Antarctica to the coast concentrates meteorites up-slope from mountains

Cross-section through the ice cap in Antarctica

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

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 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 % % % % % time in shadows at S. Pole region

Ice at the Poles from neutron data