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Much of the water now on Earth arrived during its formation, in water-bearing rocks and planetesimals. Some of the rest arrived in comets, and an unknown amount of water was lost when the impact that formed the Moon occurred (assuming that the Big Splash theory of the Moon’s formation is correct).
There is a problem with water arriving in large quantities from comets, however; water from comets seems to have a different isotope composition from water on Earth. This may be explained by assuming that most of the water arrived on objects from the asteroid belt and environs, where the isotope ratio is correct. Alternatively the early Earth might have lost hydrogen more rapidly than the heavier deuterium, which might explain the isotope ratios.
No cite but there is a theory out there that the oceans formed due to massive and ongoing electrical storms in the early Earth’s atmosphere. Water is a type of ash. It results as a reaction of hydrogen and oxygen. That’s why H2O doesn’t readily burn. It’s what’s left over, like the ash in the fireplace.
Not being a chemist or a geologist the theory makes some sense to me.
Where would the free oxygen have come from? Free oxygen is very rare in the universe and usually created by life or from dissociation of water or ice.
No1 has mentioned if that’s a possibility or probabilty yet. I don’t see how salt water can be formed without acids and alkalines being involved at some stage.
Salt is formed through surface physico-chemical processes combining bases and acids or organic compounds and acids. Usually, it’s NaOH + HCl. You have a lot of ionized Na and Cl on the Earth’s surface.
I don’t have a cite, but I seem to remember a theory about Earth’s water and this impact-to-Moon theory. Seems the violence of the impact was enough to shake out the water of hydration in some of the Earth’s rocky materials. Doesn’t seem like it would be enough, but with comets and whatnot … maybe it all adds up.
njtt mentioned in post #9 that oxygen is one of the more abundant elements in the universe, and hydrogen is the most abundant … makes sense that water is fairly common. Looking around the solar system I’d say keeping the water is the bigger problem.
It looks like there is evidence for the existence of water in the early universe:
Well… I think you’re right on the one hand - in that almost every soluble substance is at least mildly acidic or basic - and wrong on the other hand - in that the salt in the oceans is certainly not the result of a giant acidic reaction like is described with Sodium hydroxide and hydrochloric acid.
For a simple example, take calcium carbonate. Carbon dioxide dissolved in water forms a mild carbonic acid, and this is sufficient to dissolve calcium carbonate. Sodium is similar to Calcium, but even more soluble. So while calcium is mostly turned into rock and shell, sodium stays in solution almost indefinitely. Sodium and chlorine are also the most common elements in their period on the periodic table.
In an incredible case of synchronicity, I read this article this morning.
Essentially, oxygen and hydrogen found in silicates, which are abundant throughout the solar system, can react with the solar winds which are rich in free protons (i.e. hydrogens). The silicates provide one oxygen and one hydrogen atom, and the solar wind the extra hydrogen. Water.
So the sodium chloride was already there b4 the water formed?
^
It probably needed water to form. The generally accepted theory was that the oceans were originally fresh water, that eventually caught all the salt formed and consumed on land.
would that not draw us back to the question of whether the land or oceans formed 1st and it’s generally accepted that the land formed 1st. Which would mean the sodium chloride had to be there b4 the water was formed unless there were acid/alkaline reactions involved in the creation of the oceans.
Earth IS land. You just have the low parts int he surface consisting of the denser basalt which is your ocean floor, and blobs of lighter granite that are your continents. But you’re right in that NaCl might already have been forming on the surface (both basalt and granite) before the waters collected into the oceans. At least, we know the earth’s crust cooled (age of oldest meteorites) before the oceans topped off (sedimentation.)
Tangentially related.
When the Moon was formed, why was it liquid enough to form a sphere but the Earth was able to form large basins for the oceans.
You have wide lows and dry seas on the moon. More to your point, both Earth and moon have masses in excess of what will make silica and other rocks behave in a plastic manner.
Here’s a five minute clip from the History Channel about How the Moon was Formed (cool animation starts at 1:10). They say the Earth was still semi-fluid at impact.
From our scale, the oceans are huge, but on the scale of the Earth, they’re incredibly shallow. The Earth is almost perfectly smooth.
http://blogs.discovermagazine.com/badastronomy/2008/09/08/ten-things-you-dont-know-about-the-earth/
Is it possible that in the aforementioned collision that helped form the moon, that the colliding body also delivered some of the water?
The present ocean basins date from billions of years after the formation of the moon. The cratons, the core parts of the continents, are older than 2.5 billion years but are much smaller than the present continents. The rest of the continental rocks have been added by volcanism, uplift, and sedimentation since.
