Scientists may have finally discovered the answer to a long-standing question about the origin of life on Earth.

For decades, the consensus was that Earth got its water from asteroids or perhaps from a collision that led to the moon's formation.

But by looking at moonrocks, scientists discovered something else.

According to a study published Monday in the journal Proceedings of the National Academy of Sciences, the abundance of water on Earth was either here in the first place or deposited by an extremely wet (nearly pure H2O) object in the past.

This is a gigantic step forward in the history of our planet's evolution and, in turn, the preconditions for life as we know it. But it also moves our estimates of the moon's age back substantially.

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