Lunar Maria

When you look up at the Moon, you can see dark patches. These dark spots are called lunar maria. The word maria means seas in Latin. They are not really seas, though. They are flat plains made of old hardened lava.

Oceans of Lava

Long ago, the Moon had volcanoes. Hot lava flowed out of huge cracks and filled in low spots. When the lava cooled, it became smooth dark rock. People long ago thought these dark areas looked like oceans, so they called them seas. Today we know they are made of a dark rock called basalt.

Where They Are

Most lunar maria are on the side of the Moon that faces Earth. The far side of the Moon has very few of them. One famous mare is the Sea of Tranquility. That is where Apollo 11 astronauts landed in 1969. They took the first human steps on the Moon there.

Fun Facts

• The word 'mare' is said like 'MAH-ray'.
• Lunar maria cover about 16 percent of the Moon's surface.
• The dark color of maria comes from iron in the rocks.

Did You Know?

People used to think the dark areas of the Moon really were water, but space missions showed they are dried lava.