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Moon mysteries

Our solitary satellite has already told us a lot about life on Earth – and it has lots more to say

By Sharon J. Huntington / June 18, 2002

It was the moon that helped to tell us why dinosaurs disappeared. Scientists studied how impacts might have caused the craters on the moon. Their research helped others theorize how a huge rock crashing into the Earth might have wiped out many forms of life here, including the dinosaurs.

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Paul Spudis is a staff scientist and deputy director of the Lunar and Planetary Institute in Houston. He says he feels we still have a lot to learn from the moon.

"Exploring space means opening up thought and imagination," Mr. Spudis says. "We start thinking in new ways and finding solutions to problems here on Earth." He hopes we will decide to go back to the moon soon to learn more.

The moon has been associated with mysterious powers, "green" (unripened) cheese, romance, and alien invaders. Humans have long speculated about its nature and origin. Many early people believed gods lived on the moon or that the moon itself was a god. What else could explain the fact that we saw only one side of it?

The reason we see only one side is that the moon circles the Earth in the same amount of time it takes to rotate on its axis (29-1/2 days). But while the same side always faces us, all parts of the moon face the sun at different times. The moon does have a "far side," which we can never see from the Earth. But it does not have a "dark side" that never gets sunlight. (By the way, you can get a good look at a full moon on June 24.)

We see phases of the moon because sometimes the sunlit side is facing us (a full moon), sometimes only part of the side facing us is lit (gibbous and half moons), and sometimes the side facing us receives almost no light at all (new moon). (See diagram on facing page.)

When Galileo created his first telescope and looked at the moon in 1610, a better study of the moon's surface began. As telescopes improved, so did our maps and understanding of the moon's craters and its "seas" (or maria, in Latin). We know now that these aren't watery oceans but lava-filled plains. Our new knowledge helped refine theories about the moon's origin.

In his book, "The Once and Future moon" (1996), Spudis discusses some common theories and how exploration has helped us narrow down the possibilities.

Some thought the moon broke off from the Earth early in its formation and was trapped in orbit. Others said the moon was a galactic wanderer that came close enough to the Earth to be captured by its gravity. Another theory proposed that a huge rock crashed into the Earth knocking a chunk of it loose that formed into the moon. (This is sometimes called the "big whack" theory.)

When the Apollo astronauts went to the moon, we learned a lot more about its composition. The astronauts left seismographs to measure "moonquakes" and laser reflectors that are still in use. They bounce back laser pulses sent from Earth.

The rocks the astronauts brought back helped determine the age of the moon. They also hinted that the moon had an ocean of magma early in its history. These and other discoveries helped point scientists toward the "big whack" model. More research is needed to say for sure. Lunar research has also given us insights into the Earth, the solar system, and the universe.

So when are we going back to the moon to learn more? Will there ever be colonies there? NASA has no specific plans for moon missions, but it is exploring many possibilities. One is a lunar outpost where scientists could study the moon and the universe and possibly mine elements needed on Earth.

How would you design such an outpost? Consider these factors:

Air: The moon has no air. If you want to breathe, you'll have to bring a supply of air or manufacture it from elements on the moon. It's very expensive to fly anything from Earth, so you'll probably want to find a way to make your own air on the moon.

Food: There's no food on the moon either. But there are basic elements that make up food, including nitrogen, carbon, oxygen, and potassium. Could they be used to supply nutrition or breathable air?

Water: The only water on the moon is in the form of ice. Ice has been detected near both lunar poles. Oxygen could be manufactured from water.