When the Earth was young, it was a hot mess. The ground was molten lava and volcanic eruptions filled the air with poisonous gases such as hydrogen sulfide, methane and carbon dioxide. The air was so thick that it acted like a blanket, raising the temperature to 230ºC (446°F) and completely blocking out the sun. Meteors, small and large, rained down constantly from space, splashing up lava and depositing hot metals onto the Earth.
One of these meteors, called Theia, was unusually large. It was about the size of Mars, on a fateful collision course with young Earth. When it smashed into the Earth, it knocked a huge chunk of our planet right into space. But Theia didn’t leave a crater because the Earth was still half-molten, and the lava…
