In 1972, three NASA astronauts were heading to the moon. They caught a glimpse of a few continents, but all that land paled in comparison to the rest of what they saw. Over two-thirds of Earth's surface is ocean.
Life as we know it needs water, but scientists can’t figure out where Earth’s water came from. Answering that question is just one piece of an even bigger mystery: “Why are we here?”
This is the first episode in our new three-part series, Origins, about the beginnings and boundaries of life on Earth.
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