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Apollo 11 Lunar Samples

Apollo 11 regolith and breccia samples.

Left:  Apollo 11 basalt 10049. This sample has a mass of 193 grams. The ruler scale is in centimeters. Right:  Apollo 11 breccia 10018. This sample has a mass of 213 grams and is up to 8 centimeters across.

Apollo 11 carried the first geologic samples from the Moon back to Earth. In all, astronauts collected 21.6 kilograms of material, including 50 rocks, samples of the fine-grained lunar regolith (or "soil"), and two core tubes that included material from up to 13 centimeters below the Moon's surface. These samples contain no water and provide no evidence for living organisms at any time in the Moon's history.

The overall set of lunar samples collected during the Apollo program can be classified into three major rock types, basalts, breccias, and lunar highland rocks. Apollo 11 mainly collected basalts and breccias. However, small but important fragments of the Moon’s highland crust were found in some Apollo 11 breccias and were interpreted as evidence for an early “magma ocean” on the Moon. This was one of the major scientific findings of the Apollo 11 mission.

Basalts are rocks solidified from molten lava. On Earth, basalts are a common type of volcanic rock and are found in places such as Hawaii. Basalts are generally dark gray in color; when one looks at the Moon in the night sky, the dark areas are basalt. The basalts found at the Apollo 11 landing site are generally similar to basalts on Earth and are composed primarily of the minerals pyroxene and plagioclase. One difference is that the Apollo 11 basalts contain much more of the element titanium than is usually found in basalts on Earth. As a result, the mineral ilmenite is abundant in Apollo 11 basalts. Another titanium-bearing mineral, armalcolite, was first discovered in the Apollo 11 samples and was named for the first syllables of the last names of the three Apollo 11 astronauts. The basalts found at the Apollo 11 landing site range in age from 3.6 to 3.9 billion years and were formed from at least two chemically distinct magma sources. Prior to the lunar landings, some scientists thought that the Moon might have always been a cold, undifferentiated body. The discovery of basalt, which was once molten magma, disproved this hypothesis.

Breccias are rocks that are composed of fragments of older rocks. Over its long history, the Moon has been bombarded by countless meteorites. These impacts have broken many rocks up into small fragments. The heat and pressure of such impacts sometimes fuses small rock fragments into new rocks, called breccias. The Apollo 11 samples are referred to as regolith breccias because they formed by fusing material from the lunar regolith at the landing site. Many fragments can be seen in the breccia photograph shown above. The rock fragments in these breccias can include both mare basalts as well as material from the lunar highlands.

The lunar highlands are primarily a light-colored rock known as anorthosite, which consists primarily of the mineral plagioclase. It is very rare to find rocks on Earth that are virtually pure plagioclase. On Apollo 11, small fragments of anorthosite were found in some of the breccias. On later missions, the crews were specifically trained to look for large samples of anorthosite, with important samples being returned by Apollos 15 and 16.

On the Moon, it is believed that the anorthosite layer in the highland crust formed very early in the Moon's history when much of the Moon's outer layers were molten. This stage in lunar history is now known as the magma ocean. The plagioclase-rich anorthosite floated on the magma ocean like icebergs in the Earth's oceans. The magma ocean hypothesis of an early, molten Moon was first developed from studies of the chemistry of Apollo 11 samples, although the term “magma ocean” was not actually used until a few years later. The magma ocean stage occurred 4.3 to 4.5 billion years ago, during the Moon’s initial formation. After the Moon cooled and solidified, small portions of the Moon remelted to form the basalts found at the Apollo 11 landing site and other parts of the Moon, in some cases more than a billion years after the Moon formed.

 Return to Apollo 11 Mission Overview

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