Two papers are coming out this week that radically change our conceptions of early oceans on Earth. Both papers are being published in Nature which gives them a lot of credibility.
In one paper, two Stanford University researchers have concluded that the planet's oceans cooled a billion years earlier than previously thought. Instead of having oceans around 85c around 3.4 billion years ago, Michael Hren and Mike Tice have postulated, based on the hydrogen and carbon ratios, that the oceans were actually no more than 40c. That's a change from near boiling hot to just warm bathtub water.
One of the reasons for this change in analysis is that traditionally researchers just use the oxygen isotope ratio to determine temperature and they assume that the oceans of yesterday (and 3.4 billion years is a lot of yesterdays) had the same chemical composition as the ocean do today. Hren and Tice, on the other hand, decided to challenge that assumption and their analysis shows that there's been a dramatic change in those billions of years. Atmospheric and oceanic. This creates quite a different environment for the early one celled organisms that were alive at the time.
The second paper concludes that Earth's oceans are made from extraterrestrial material. Ice from asteroids, presumably.
Francis Albarède, the author of the study, concluded that this happened 4.5 billion years ago.
According to the textbooks I read when I was in school, the ocean and the atmosphere were formed from volcanic gases around a billion years after Earth was formed. The Earth's interior was the source of these volatile elements. But this never made a lot of sense because the rocks of the Earth's mantle are deficient in water and couldn't have provided anywhere near enough water for that to occur. Giving credit for that watery event to the asteroids is neat. Maybe they'll be rewriting a few textbooks soon. Hell, they need to take