Oxygen is the third-most abundant element in the universe, because the universe contains a lot of stars.
About 21 percent of the Earth's atmosphere is oxygen. So where has it come from? Distant stars?! If this were the case, then all of the solar system planets should have oxygen of the same quantity, or in a very close percentage, because they are relatively close to each other.
Stars are all over the universe, but the amount of oxygen on Earth is not increasing. So the source cannot be any general stars, but a very special one! And that very special star must "not" be in existence today; otherwise the amount of oxygen will increase.
From the Rust on Mars, we can tell that the second sun was an oxygen-rich star, otherwise the rust wouldn't have formed. And we saw in that section that the second sun has produced large quantities of water vapor (H2O) mixed with iron particles in order to produce rust.
What makes the Earth different from the other planets in terms of the oxygen quantity is very likely the distance of Earth from the second sun and maybe also the Earth was orbiting between the two suns all the time, like the picture to the right!
In the beginning all of the planets were in a gas form, and most likely they were very close to each other (Solar System Formation). The stars formed first and ignited, but they were not very hot, because they were very new.
It is very likely the second sun stormed earth with water vapor when the planets were close to each other, for a very long period of time, and earth was orbiting in between, and when the second sun was "not" very hot.
Now regardless whether the way of oxygen and water transfer that we are
assuming here is correct or not, the point is that the source of oxygen and water is stars; and since there are signs
pointing to a second star once existed in the solar system that was capable of
producing oxygen and water, then that star must have been the source.
The Cambrian Explosion
An Artwork of Life in the Cambrian Period
Since life on Earth started only in the Cambrian period, we have to rule out the presence of water on the surface of Earth in any form, ice or liquid, before the Cambrian. Needless to say there is no physical evidence to show otherwise.
It looks like the water vapor received from the second sun at the time of formation has concentrated in a lower layer of the Earth's interior. Later on, after the Earth's crust solidified, and for some dynamic and/or chemical process, water vapor started to come close to the surface of Earth, specifically in the upper part of the Earth's mantle.
We have seen in the section about the formation of the solar system that the moon's initial position was the first planet near the Sun, and then shifted. It is very possible that the moon has come to orbit Earth at this time (in the Cambrian period) and caused the dynamic effects that forced the water to come close to the surface of Earth, in the upper part of the Earth's mantle.
When the water vapor came close to the upper part of the Earth's mantle, it started to come out from volcanic eruptions and forms clouds and then rain. And until this day, volcanoes produce water vapor that makes clouds and rain. More than 70% of the volcanic gases is water vapor.
Ice crater on Mars
The amount of water in Earth must have increased when the second sun entered its final period of life and started releasing huge amounts of water vapor. Large amounts of this water vapor must have frozen, and then fallen on earth in the form of ice. The evidence of ice is found in the ice craters on Mars.
The water on Earth is of a fixed quantity, but part of it seems to sink to
the mantle via cracks in one way or another, and then it is regenerated again in
the form of water vapor (H2O) via volcanoes
and cracks in the earth's mantle.
Water in the asteroid belt
Artwork of the dwarf planet (asteroid) Ceres
QUOTE: "Dwarf planet
may contain more freshwater
Ceres is an icy object; with a diameter of about 950 km; orbiting in the outer edge of asteroid belt; far away from the sun heat. It is very likely a rock with water ice building on it.
Every single object orbits in the asteroid belt in the present time gives an idea about an attribute of the original object that used to orbit there in the past, and Ceres is no exception. It is a leftover sign indicating that the object that used to exist in the asteroid belt was a generator of oxygen and water.