>>12154816My oceanography class gave the argument that water was formed from the rocks. As the Earth cooled, chemical processes broke apart the molecules in the rock forming water from the hydrogen and oxygen.
My Historical Geology class argued it came from space. During the late heavy bombardment meteors brought water to earth in the form of ice crystals and seeded the earth with enough water to form the oceans. This one is problematic because evidence shows water was already on the Earth during the late heavy bombardment and Earth's isotope signature isn't the same as it is in the solar system. However the math is good, you CAN create the oceans from the expected volume of water from space and water is brought to Earth this way still to this day.
My introduction to climate class argued that it came from high end ultraviolet radiation from the sun breaking apart nitric oxide and methane in the atmosphere that recombined to form water vapor.
The isotope signature on Earth for water is unfortunately unique to Earth. It's likely a case of the first two arguments combined. The 3rd argument may account for some water in the atmosphere but is ultimately bonkers. The mechanism is just too slow.
