Sunday, October 11, 2009

The Moon Is A Rosetta Stone Of The Planets And Is The Closest One To The Earth.

The moon is one of thirty-two satellites that circle about the nine planets of the solar system. It is a quarter the size of the earth, weighs one-eightieth as much, and moves in a nearly circular orbit at a distance of a quarter of a million miles from us.

The moon is undistinguished among its sister satellites in nearly every respect. Lacking an atmosphere and oceans, it is a poor piece of real estate and a most unlikely abode for life. Yet, the very features of the moon which make it undesirable for colonization also endow it with a unique scientific value.

The moon has preserved the record of its past for an exceptionally long time; it holds clues to the early history of the solar system which are unavailable on any other neighboring body. On the earth, the atmosphere and the oceans wear away surface features in 10 to 50 million years, and mountain-building activity turns over large areas of the surface in about the same time. There is little left on the earth of the features that existed several hundred million or a billion years ago.

But on the moon there are no oceans and atmosphere to destroy the surface, and there is relatively little of the mountain-building activity which rapidly changes the face of the earth. Over large areas of the moon, the materials of the surface are as well-preserved as if they had been in cold storage.

Many craters are circled by ramparts ranging up to 10,000 feet in height. Some of these ramparts must be a billion years old or more, yet photographs taken with a telescope clearly indicate that they have been preserved almost unchanged, with little of the original material worn away. On the earth, a mountain 10,000 feet high is worn away in the relatively short time of 100 million years.

Why does the moon lack air and water, which are abundant on the earth? The answer is connected with the small size of the moon and the weak pull of gravity at its surface. The atmosphere of any moon or planet quickly drifts away into space if it is not held in place at the surface by the force of gravity. Even with gravity there is always a steady leakage of gas from the atmosphere into space.

The smaller the planet, the less the pull of its gravity, and the greater the leakage rate. The moon is so small that all the gases originally present in its atmosphere, including water vapor, escaped quickly when it was still very young. If no life exists on the moon, what is the scientific interest of lunar exploration? A large part of the answer is connected with the excellent state of preservation of the moon.

The piece of rock that the astronauts bring back to the earth will almost surely contain no life; it will probably contain no gold or silver; but, nonetheless, it will be scientifically priceless because of the revelations it can offer regarding the history of the solar system. Alan Benson


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