[userulluipeste]

"Other scientists agree that some amount of water could have formed on Earth — but perhaps not nearly enough to produce its oceans." "Earth might have been a water factory for only a moment, but that moment may have been enough to forge oceans."

Well, our planet has magnetosphere and it also had life for a long time already. Although the magnetosphere reduces the influx of Hydrogen in form of solar wind proton bombardment, it also prevents the loss of Hydrogen that managed to get captured on Earth by not letting it be blown away from the upper layers of atmosphere. Life at one point, almost two and a half billion years ago, caused the Great Oxygenation Event, in which the entire atmosphere got Oxygen rich. This very special atmosphere (for all that time) made it possible for the incoming Hydrogen (be it from the Sun, other stars, or just as the most common form of dust in the universe blown in here from whatever direction and cause) to ultimately be collected as water. Two and a half billion years, that's a lot of time to accrue water. It ought to show, at some point. So it's at least one pair of factors that could have led to a surplus of water we see today, besides what might have existed from very beginning.

[chistev]

> Well, our planet has magnetosphere and it also had life for a long time already.

But life needed water as a requirement to arrive, right? So are you saying that there was a little bit of water for life to get started, before that same life caused the oxygenation event to create more water over millions of years?

Please explain, thank you.

[userulluipeste]

Well, yes -- some amount of water must have been in there from very beginning, plus what may have fallen in as icy bodies from outer space afterwards, this much is mentioned in the article itself. The question was not if there was water, but how much of it. Most of today's planetary body of water resides in deep depressions -- seas and oceans, which is very different to what must have been initially. Back then, the surface supposedly had very little relief, due to Earth's crust being much thinner at that time. That meant that, whatever water was there, it must have been shallow, spread to very large areas.¹ This condition was especially propitious for life, as it provided ample space for life to proliferate. The first organisms must have been at the bottom of this large, never drying shallow "ocean" or mesh of (at least often) connected seas. Deep enough to shield the emerging life from UV light, but shallow enough for light to reach the developing life, including the first unicellular algae. Even today, most of life lives on the shallow waters, where plants could find minerals and underwater sunlight, and thus the whole food chain above them could be sustained.

¹ Today's amount of water spread all over an Earth with no relief gives you a kilometers-depth ocean. Even with only some modest amount of relief (as it should have been at the beginning), if it didn't reached the water surface to produce shallow waters, then that's a non-starter for life. The life should have waited a lot of time for the Earth to cool down, for the crust get ticker and thus for a more prominent relief to appear in order for it to finally get any chance to emerge. Therefore, it was very important for life to encounter an environment with just modest amount of water.

[chistev]

Thanks for taking the time.

[rrgok]

Is this a chicken and egg like question?