Lunar Maria

moon · space · geology · ancient

Dark volcanic plains. Lunar maria are huge, flat areas on the Moon that look dark because they're made of basalt, a dark volcanic rock rich in iron. This makes them much darker than the bright, rocky highlands surrounding them.

Created by ancient lava. Billions of years ago, enormous asteroids smashed into the Moon and created giant craters. Lava from deep inside the Moon flowed up and filled these craters like water filling a bowl, creating the maria we see today.

Mostly visible from Earth. The maria cover about 16% of the Moon's surface, and most of them are on the side facing us, which is why they're so easy to spot. The far side of the Moon has very few maria, and they're much smaller than the ones we can see.

Visible to the naked eye. Ancient people saw the dark patches on the Moon and called them 'maria,' which means 'seas' in Latin, because they thought they were oceans. We still use that name today, even though we know they're actually dry plains of rock.