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Pristine Sample Laboratory Display Cabinet

A display cabinet is located at one end of the Pristine Laboratory. It contains one Apollo 16 and two Apollo 15 samples which are representative of the rocks in the lunar sample collection. Note that this cabinet represents one exception to the rule that samples from different missions are not housed in the same cabinet at the same time. The Lunar Sample Curator discusses aamples in the display cabinet with a visiting scientist.

Image of lunar rock 15459
15459, a 5.9 kg rock, was collected just inside the rim of a 100-meter diameter crater on the foot of the mountains overlooking the Apollo 15 landing site. The rock is a tough, coherent regolith breccia - composed of rock fragments and other soil components such as small glass spheres and glass shards bonded together in a glassy matrix. Breccias such as 15459 are formed in ancient regoliths by meteorite impacts in which heat and pressure bond rock fragments and soil particles together. Impacts not only fuse rocks from regolith particles, but break rocks into small fragments and fling these fragments and blobs of molten glass some distance into the surrounding area. Rock fragments, called clasts, found inside breccias like 15459, can represent material thrown from the surrounding areas by prior impacts. Clasts in 15459 are diverse; some are mare basalts from the lava-filled plains and others are from the older highlands. One basalt clast crystallized 3.3 billion years ago, although the age of formation of the breccia now called 15459 might be as recent as 500 million years ago or less.

15556, a 1.5 kg rock, was plucked from near the rim of Hadley Rille at the Apollo 15 site. From the rim of Hadley, astronauts could see layers of basalt exposed in the wall of the rille, which is interpreted as an ancient lava channel. This medium grained, extremely vesicular basalt is 3.4 billion years old. Since the Moon is so very dry, the volatile gas causing the vesicles (bubble cavities) in this rock and other rocks probably was a mix of oxides of carbon and sulfur dissolved in the molten rock. 15556

Image of lunar rock 61016
A close-up view of 1 milimeter diameter zap pits on Apollo 16 sample 64455 shows craters lined with black glass surrounded by a white halo of shocked rock.
61016, at 11.7 kg, was the largest rock collected during the Apollo missions. It was nick-named "Big Muley" after one member of the geology support team. Apollo 16 landed in the light-colored highlands of the Moon. These highlands regions are generally higher in elevation and composed of older rocks relative to the volcanic plains. These rocks are rich in aluminum and calcium, two of the elements found in the plagioclase mineral anorthite. This specimen is comprised of four different rock types: 1) material of basaltic composition melted during an impact; 2) an impact-shocked anorthosite, thought to be from ancient lunar crust; 3) an impact shock-melted glass rich in aluminum and calcium; and 4) a darker glass coating. Some components in this rock may be as old as 4.5 billion years. Zap pits, or tiny craters created by micrometeorites striking the lunar surface at very high speeds, are prominent on one side of this rock, but absent on the other. Since the pitless side was facing up when the astronauts found the rock, it must have only recently been turned over by natural processes.

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