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Moon Rocks

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When the astronauts visited the moon, they brought rock samples back to the Earth. Over thirty years later, what is known about them?

From 1969 to 1972, six Apollo missions returned to Earth with 382 kilograms (842 pounds) of lunar rocks, core samples, pebbles, sand and dust. The 842 pounds of rock are actually 2200 separate samples from six different lunar sites.

How were the samples collected? Collecting moon rocks illustrates how the rocks were collected, the sampling procedure used and how they were stored for shipment back to Earth. Once back on Earth, the samples had to be stored. The Lunar sample laboratory facility became the new home for the moon rocks. Take a tour of the various areas.

Samples were collected by Apollo missions 11 through 17 (Apollo 13 did not land on the moon). This collection of web pages (the Apollo missions) gives an overview of the rocks collected and the sites.

All rocks collected are igneous - formed by cooling lava. The mission failed to find any sedimentary rocks - those deposited by water - on the moon. The moon rocks were found to contain no water and were formed in an environment lacking free oxygen. Iron then occurs as crystals of metallic iron. Exposure to Earth's atmosphere would result in the rocks rusting. A new mineral, Armalcolite, was found by the Apollo 11 astronauts. It was later discovered on Earth.

Some of the samples collected were identified as basalts. Basalts were collected from two areas: the darker surface of the moon called "maria" or sea - smooth, level, mostly crater free areas and the lighter surface of the moon called highlands - higher in elevation and heavily cratered areas. Maria rocks are estimated to be between 3.1 to 3.9 billion years old. Highland rocks are estimated to be 4.0 to 4.3 billion years old.

One particular well-known sample is the "genesis rock". The genesis rock was collected during the Apollo 15 mission. It is a white anorthositic rock. Anorthite is a mineral. It is calcium rich plagioclase feldspar, plentiful in the lunar crust, but not commonly found on Earth. Scientists determined that the genesis rock was about 4 million years old - nearly as old as the moon itself.

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