Rosetta’s Instruments Direct Scientists to Look Elsewhere for the Source of Earth’s Water
Illustration of a rocky planet’s being bombarded by comets. Earth may have appeared similarly early in its development. While indeed such comet impacts did occur, new in situ observations by Rosetta of comet 67P indicate that comets were likely not the primary source of water delivered to the Earth. (Image credit: NASA/JPL-Caltech)
Where did all of our water come from? What might seem like a simple question has challenged and intrigued planetary scientists for decades. So results just released by Rosetta mission scientists have been much anticipated and the observations of the Rosetta spacecraft instruments are telling us to look elsewhere. The water of comet 67P/Churyumov-Gerasimenko does not resemble Earth’s water.
Because the Earth was extremely hot early in its formation, scientists believe that Earth’s original water should have boiled away like that from a boiling kettle. Prevailing theories have considered two sources for a later delivery of water to the surface of the Earth once conditions had cooled. One is comets and the other is asteroids. Surely some water arrived from both sources, but the question has been which one is the predominant source.