Earth didn’t always have a moon. In the beginning of the solar system, when the planets were still forming, something happened that would change Earth’s night sky forever: The Moon was created!

How did it happen? This episode, co-host Regina G. Barber searches for answers with planetary scientists. With co-host Emily Kwong, they discuss how the moon was likely made, how scientists know and what that might mean for where Earth’s water came from.

Check out Regina's reporting on hydrothermal vents.

Interested in more planetary science? Email us your question at shortwave@npr.org.

Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.

A previous version of this episode mischaracterized a scientific hypothesis. The episode incorrectly said the idea is that hydrothermal vents may have been the origin of water on Earth. In fact, the hypothesis is that life may have come from hydrothermal vents.

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Where did our moon come from?

Short Wave

Where did our moon come from?