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Eventually the ocean began to form. As as soon as the temperature fell to about room temperature, then rain could begin. The presence of running water made some of the gases in the atmosphere, like carbon dioxide, dissolve into the forming ocean. Scientists think that the Earth's secondary atmosphere may have come to be dominated by nitrogen because it alone of all the gases comprising the secondary atmosphere does not easily dissolve in water.
Life may be begun on Earth in this early ocean. The ocean also may be become the earliest "dump" for the waste products of the activity of early life on Earth. Such waste products included iron.
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