Billions of years ago, another planet smashed into Earth. An event of this epicness could have created our Moon. It also could have brought alien life to our planet. What evidence of this planet still exists on Earth today?

As I found while working on my own novel, writing about aliens can be strangely helpful in this pursuit. Just as astronomers use telescopes to examine celestial objects light-years away, novelists can invoke imagined civilizations to reveal truths closer to home,

Scientists are listening in on sperm whale conversations and studying Earth's strangest microbes to prepare humanity for first contact with extraterrestrial life.

To travel between solar systems, a spacecraft would need extremely sophisticated – if not impossible – technology.