Water isn't just delivered to planets by comets and asteroids — it can also be forged as worlds form, a new study finds.
For decades, scientists have debated the origin of Earth's water. One long-standing theory suggests that it was delivered by icy bodies from the outer solar system after Earth formed, while another proposes that the raw materials that make up our planet already held the ingredients necessary to generate water internally. Until now, however, this second hypothesis had never been tested under realistic laboratory conditions.
