Where Did Earth Get Its Oceans? Maybe It Made Them Itself. | Quanta Magazine

At first, scientists thought Earth’s water came from comets. Then, asteroids. Now, they wonder if Earth’s water is homegrown.

Introduction

At this moment, a spacecraft is headed from Earth to Europa, an ice-veiled moon of Jupiter thought to contain an ocean similar in some ways to one of our own. NASA engraved a metal plate affixed to the spacecraft with a poem, commissioned from Ada Limón during her time as poet laureate of the United States. It reads, in part:

And it is not darkness that unites us,

not the cold distance of space, but