What if we dropped the "terrestrial" from "extraterrestrial"? Scientists recently explored the intriguing possibility that alien life may not need a planet to support itself.

At first glance, planets seem like the ideal locations to find life. After all, the only known place life is known to exist is Earth's surface. And Earth is pretty nice. Our planet has a deep gravitational well that keeps everything in place and a thick atmosphere that keeps surface temperatures in the right ranges to maintain liquid water. We have an abundance of elements like carbon and oxygen to form the building blocks of biological organisms. And we have plenty of sunlight beaming at us, providing an essentially limitless source of free energy.

It's from this basic setup that we organize our searches for life elsewhere in the universe. Sure, there might be exotic environments or crazy chemistries involved, but we still assume that life exists on planets because planets are so naturally suited to life as we know it.