Earth has a moon. Its 'twin' doesn't; Scientists think they know why

Venus and Earth are similar in size and composition, yet Venus lacks a moon while Earth has one. A UC Riverside study suggests Venus may once had a moon, but its slow 243-day rotation pulled it inward to crash into the planet, unlike Earth's Moon which moves away at 4 cm yearly.

When I made this discovery, I was shocked. I thought surely the broad range of scenarios I was exploring would lead to a variety of results. But it all went pretty much in the same direction.