It used to be thought that the unusual amount of water on our planet was the result of a giant collision between proto-Earth and a dwarf planet or planetoid called Theia. I recently heard of some oxygen isotope research which indicates that the giant impact hypothesis wasn't necessary to explain the oceans. So is the giant impact hypothesis still alive, modified or dead?
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The giant impact hypothesis was not formulated to address the issue of how the Earth acquired its waters. At the time the giant impact hypothesis was formulated, the dominant theory for how the Earth acquired its waters was impacts by comets and wet asteroids during the late heavy bombardment.
The giant impact hypothesis was instead formulated to address the issue of how the Earth acquired its very large moon.
answered Dec 15, 2015 at 13:37