Moon's Symbol

The Moon: Earth's Satellite


Boy with map


A crater containing a pond of ice was recently discovered on the dark side of the Moon. The crater is believed to be twice the size of Puerto Rico and deeper than Mt. Everest is high! The ice is believed to be a remnant of a comet which crashed into the Moon 3.6 billion years ago.

The Moon travels around Earth in an oval orbit at 3680 kilometers per hour. The Moon does not have an atmosphere, so temperatures range from -184 degrees Celsius during its night to 214 degrees Celsius during its day except at the poles where the temperature is a constant -96 degrees Celsius. The Moon is actually a little lopsided due to the lunar crust being thicker on one side than the other. When you look at the Moon, you will see dark and light areas. The dark areas are young plains called maria and are composed of basalt. The basalt flowed in and flooded the area created by a huge impact with an asteroid or comet. The light areas are the highlands, which are mountains that were uplifted as a result of impacts. The lunar surface is covered by a fine-grained soil called "regolith" which results from the constant bombardment of the lunar rocks by small meteorites. Scientists theorize that the Moon was the result of a collision between Earth and an object the size of Mars. One theory states that the debris from the impact was hurtled into space where, due to gravity, it combined. This resulted in the formation of the Moon. The gravitational pull of the Moon on the Earth affects the ocean tides on Earth. The closer the Moon is to Earth, the greater the effect. The time between high tides is about 12 hours and 25 minutes.

The Moon (seen from Apollo 17)
The Moon
The phases, or changing appearance, of the Moon depend on its position relative to the position of the Sun. When the Moon is between the Sun and the Earth, the side of the Moon facing the Earth is dark. This is called a "new moon". As the Moon travels eastward in its orbit, more of its sunlit side becomes visible to Earth and the Moon is said to be "waxing". More specifically, the phase after a new moon is called a "waxing crescent" because we can see no more than a quarter of the Moon at this point. As the Moon continues eastward, the Sun, Moon, and Earth form a 90 degree angle and the Moon appears half dark and half light to us here on Earth. This is a "first quarter" phase. After the first quarter phase, more than a quarter of the Moon is visible to us, so it is now in a "waxing gibbous" phase. As the Moon continues its revolution around Earth, the Sun, Earth, and Moon align with the Earth in the middle. The side of the Moon facing Earth is now fully lit. This is called a "full moon" phase. As the Moon travels further around in its orbit, the lit portion of the Moon visible to Earth becomes smaller, so the Moon is now said to be "waning" as it enters the next phase. After the "waning gibbous" phase, the Moon enters the "third quarter" phase where once again the Moon appears half dark and half light from Earth. As it completes its revolution around Earth, the Moon enters a "waning crescent" phase just prior to starting the cycle again as a new moon.

StarTell me more about the phases of the Moon!

A Question

When we look at the Moon, it has light and dark areas which give it the appearance of a man's face. In actuality, what are the light and dark areas?

Girl using telescope

The Facts
The Facts

DId you know?
Did you know?

The Answer
The Answer


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StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Curator: J.D. Myers
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