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SESK: Stuff Everyone Should Know · sesk.info/aero-moon-maria-lava

What are the dark patches you can see on the Moon?

Maria, huge basins filled long ago with lava.

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  1. Oceans of water
  2. Basins filled with old lava ✔
  3. Shadows of tall mountains

Why: Early astronomers thought the dark areas were seas, so they named them maria, Latin for seas. They are really giant impact basins that filled with lava billions of years ago. The light areas are highlands.

Huh, didn't know that: The lava that filled the maria flowed between about 4.2 and 1.2 billion years ago.

The dad joke
Why did the Moon go to the beach? To see its maria, but there was no water.
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References

Answer: Basins filled with old lava. Early astronomers thought the dark areas were seas, so they named them maria, Latin for seas. They are really giant impact basins that filled with lava billions of years ago. The light areas are highlands.

  1. NASA Science: Earth's Moon Facts science.nasa.gov/moon/facts
    The dark features, called maria (Latin for seas), are impact basins that were filled with lava
    Checked 2026-10-10.

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