People who write about water like to say that the liquid in our drinking glasses and toilet bowls has been with us since the age of dinosaurs, continually recycled through plants, animals (including us) and the atmosphere. But really, some of the water on (and in) Earth was here billions of years before T. rex terrorized Triceratops. And now, research released today shows that, nearly 4.5 billion years ago, Earth shared some of that water with the Moon.
It was around that time that a Mars-size object collided with Earth, or so the Giant Impact theory goes. Debris released from the impact object became locked in orbit around the planet, eventually coming together to form our Moon.
The theory also used to go that the Moon was originally dry, any water present during the collision wouldn't have survived impact. Water found on the moon would have had to come from ...
