The usual theory of the formation of planet Earth describes an
incandescent aggregation of matter which eventually cools down to a
state which permits the existence of life forms. Plausible, for we
know the Earth's core is still very hot. So: whatever the origin of
the hydrosphere (some say it is from extraterrestial sources, such as
comets), where did the oxygen in good old H2O
come from? It could not have existed in a fiery ball, or could it?
Most descriptions of planetary atmospheres ( excepting Earth) posit
hydrogen, methane, ammonia, but never oxygen. Outer space contains
hydrogen. What gives?
monroe22-ga

Hi monroe22!!


This is the brief story:

The very first Earth's atmosphere probably consisted of helium,
hydrogen, ammonia and methane.
Then the Earth's atmosphere was changed its composition by the
offgassing of the Earth's mantle, the process in which gasses were
expelled from the earth's interior (volcanoes).
If we assume that volcanoes five billion years ago emitted the same
gasses as they do today, the earth's atmosphere probably increased the
amount of water vapor, carbon dioxide, and nitrogen with time. No
molecular Oxygen was present!!.
Due the absence of molecular oxygen, the early Earth's atmosphere is
called a reducing atmosphere.
The vast amounts of water vapor expelled by the volcanic earth
resulted in the formation of clouds which, in turn, produced rain.
Over a period of thousands of years, the rain accumulated as rivers
and lake and ocean basins.
 
From this scenario the main source of molecular oxygen was the water vapour:
Water vapour is dissociated by ultraviolet radiation in the upper
atmosphere to give hydrogen, most of which escapes into space, and
oxygen which is retained by the earth's gravitational field:
2H2O (+ UV) ?-->  2H2 + O2  !!

A second important mechanism for the production of oxygen is
photosynthesis by living organisms:
Photosynthesis is the process by which water is converted, i.e.,
oxydized, into molecular oxygen (and by which carbon dioxide is
subsequently reduced to form carbohydrate).
Note that due oxygen ractivity life cannot evolve in an atmosphere
plenty of oxygen because the presence of molecular oxygen would be
expected to destroy (oxidize) the many reduced organic compounds used
by and making up life.
The  invention of photosynthesis did not lead to a rapid increase in
the molecular oxygen content of the atmosphere: the presence of vast
reserves of reduced elements in the Earth's crust served as molecular
oxygen sinks. It wasn't until all of these reduced elements had been
fully oxidized that molecular oxygen would stably exist in the Earth's
atmosphere. Affortunately for us, this process gave to the new living
organisms the necessary time to develop the defenses against the
poisoness consequences of prolonged exposure to molecular oxygen.
The rate of oxygen production by photosynthesis is extremely high, and
it is estimated that at the present time all the oxygen in the
atmosphere passes through the photosynthetic cycle in 2000 years, and
all the carbon dioxide in 300 years.
 

Sources:
"History of Earth"
http://www.mansfield.ohio-state.edu/~sabedon/biol1010.htm 

"Walton, J. C. --- The Chemical Composition of the Earth's Original Atmosphere"
http://www.grisda.org/origins/03066.htm

----------------------------------------------------------

Additional references:

"History of Life - How did chemisty and oceans produce this?":
http://darkwing.uoregon.edu/~bsl/astronomy/

"Surviving With - and Without - Oxygen "
http://www.astrobio.net/news/article878.html

"When Did Earth's Oceans Become Oxygenated?":
http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=280

"Science & Technology at Scientific American.com:
 Where did the earth's atmospheric oxygen come from? If it was
generated by plants via photosynthesis, then where did all the reduced
carbon go (the fossil-fuel reserves don't seem nearly large enough)?
Could some of the oxygen have come from water that was split by
ultraviolet rays?"
http://www.sciam.com/askexpert_question.cfm?articleID=000E9FDF-CBC1-1C71-9EB7809EC588F2D7&catID=3&topicID=10

"Nobel Display-Origin of Oxygen in the Atmosphere"
http://www.gustavus.edu/oncampus/academics/geology/nobel_display/nobel_bif.html

-----------------------------------------------------------

Search strategy:
origin "oxygen come from"
origin oxygen atmosphere


I hope that this helps you. Please feel free to request for a
clarification if you need it, I will gladly respond to your requests.


Best regards.
livioflores-ga

---

Request for Answer Clarification by monroe22-ga on 29 Aug 2004 11:32 PDT

livioflores-ga: Very nice, but I've read variations of that scenario
many times. Allow me to repeat the question: How did the oxygen
originate in the red hot ball that became Earth? If you reply: It was
chemically bound as silicates in the primordial rocks in the
proto-solar system, that would be dodging the issue; how did the
primordial rock acquire oxygen? If volcanoes expelled water vapor,
where did the water come from? After all outer space seems not to
contain oxygen. If the ultimate answer is: Well, all elements were
created by the big bang, one may as well say God created everything.
So , once more, where did the primordial elemental oxygen originate,
and when and where did it bind to hydrogen to form H2O. (P.S.: I am a
chemist, so get as technical as you please.) Thanks, monroe22

---

Clarification of Answer by livioflores-ga on 29 Aug 2004 22:23 PDT

Hi monroe22!!

Ok, you feel that my answer is not good enough, I can accept that. But
I will use this feature to try to give you a better answer about this
topic.

First of all my apologizes forthe error that you found in the
www.gustavus reference, but I am not a chemist (only a web researcher)
so I did not noted such mistake. Note that the answer did not use this
reference, I only post it as additional for further reading.


Now the new answer:

Despite my low level knowledgement, after research for this comment I
must disagree with the opinion that the presence of oxygen and water
in the Earth and the Universe (interstellar space) cannot be explained
by today sciencist.


Here is exposed my position about this:

Shortly after the Big Bang nuclear reaction produced almost Hydrogen
and Helium of the Universe, but almost none of the heavier elements.

Some regions of the young universe would have had slightly higher
densities than others. The gravitational attraction in those regions
have promoted the formation of galaxies and stars by collapsing their
extra matter, starting from about two billion years after the Big
Bang. Some of the early stars would have been more massive than our
Sun, with enough mass to burn the original hydrogen and helium, into
heavier elements, such as carbon, oxygen, and iron. This could have
taken only a few hundred million years. After that, some of the stars
would have exploded as supernovas, and scattered the heavy elements
back into space, to form the raw material for later generations of
stars.

After hydrogen fusion, stars heavier than eight times the mass of the
Sun can go on to convert helium into carbon and oxygen, followed by
the formation of magnesium and silicon and ultimately iron.

"A star the size of the Sun will burn hydrogen into helium until the
hydrogen in the core is exhausted. At this point, the core of the star
contracts and heats up until the fusion of three He nuclei into C can
begin. Stars in this stage of evolution are known as red giants. Low
mass stars such as our Sun will then evolve into a compact object
called a white dwarf. All nuclear reactions in a white dwarf have
stopped. Higher mass stars have internal temperatures (10^8ēK) that
allow the fusion of carbon with helium to produce oxygen nuclei and
energy. For very massive stars, the exothermic fusion of low-mass
nuclei into successively more massive nuclei can proceed all the way
up to nuclei in the iron region."
From "Origin of the Elements":
http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap10.pdf


Elements heavier than iron are formed during the explosion of a
supernova:   When a large star's has consumed all its "atomic fuel"
finally collapses, then explodes and propells almost its matter into
space and also produces neutrons. This neutrons collide with the
elements from the star, building heavier elements, which are also
propelled into space by the force of the explosion.
The elements formed by nucleosynthesis in the red giant and during the
supernova become part of the interstellar dust.
Our Solar System was formed from one of this clouds of intestellar
dust about 4.6 billion years ago. This cloud had almost all the
elements that we find today in our solar system including oxygen.

"A region of the interstellar dust became progressively denser due to
gravitational attraction between the particles. Ultimately, it became
dense enough so that collisions produced larger and larger and larger
bodies (planetesimals) and ultimately, the sun and planets.
Once the formation of larger bodies commenced, the solar system formed
rapidly, probably within a few million years.
In our solar system, about 99% of the mass of the nebula went into the
sun.   The sun's composition is therefore very close to that of the
original nebula, mostly hydrogen and helium.
When the sun ignited (became dense enough so that fusion of hydrogen
to helium began), it released intense radiation (solar wind) that
swept most of the volatile, or gaseous, elements out of the inner
solar system.
The "lost" elements included most of the hydrogen and helium, plus
much of the carbon and oxygen. H, He, C, O.
The elements remaining to form the Earth were mainly oxygen (bound to
metals), silicon, iron, aluminum, calcium, magnesium, sodium, and
potassium. These make up most of the rocks on the Earth today. O, Si,
Fe, Al, Ca, Mg, Na, K."
From "MSL111: Notes: The Origin of the Oceans"
http://www.sfos.uaf.edu/msl111/notes/origin.html
  

Note that you have interstellar clouds with hydrogen and oxygen, water
is formed in this interstellar medium.

"Cosmically, water is not uniformally abundant, its incorporation into
Earth-sized planets not necessarily constant, nor is its planetary
manifestation as aquatic habitats suitable for life a given. The
search for life in the universe must account for these variations and
the uncertainties that
accompany them. Water is formed in the interstellar medium and in the
denser molecular clouds that give rise to star-forming regions.
Differences in elemental abundance, gas-phase chemistry, and grain
chemistry will result in measurable variation in the abundance of
water in those regions. Water is a significant source of infrared
opacity in collapsing cloud cores and protostellar disks; the
efficiency at which the collapsing gas cools may control the stability
against gravitational fragmentation and the formation of binary or
multiple systems (including brown dwarf companions). The abundance of
water in protoplanetary disks is a sensitive function of the oxidation
state of the nebula and, to first order, the elemental ratio of carbon
to oxygen: the C/O ratio has been observed to vary significantly from
star to star, implying that there may be very ?wet? as well as ?dry?
planetary systems. Furthermore, the cosmochemical record in meteorites
shows that a large range in oxidation states and water abundance
existed in the early Solar System, perhaps as a result of removal of
water from the warm interior of the primordial nebula and its
condensation at greater distances. Presumably, planets formed from
different mixing ratios of this primitive material would be endowed
with different initial inventories of water. The total planetary
inventory of water may also depend on the presence of giant planets
and the efficiency of its dynamical transport as icy bodies from the
outer regions of a planetary system."
From "Water and Life in the Universe" from Institute for Astronomy at
University of Hawaii:
I suggest you to read this document.
http://www.ifa.hawaii.edu/UHNAI/Intro.pdf


Additional references:
(If one of them has a mistake, please forgive for that, thank you)

"Origin and Chemical Evolution of the Elements"
http://origins.colorado.edu/uvconf/white_final/node5.html

"Origin and Chemical Evolution of the Elements - Figure 7: Central
regions of the oxygen-rich supernova remnant"
http://origins.colorado.edu/uvconf/white_final/node5.html#N132D


"Water in the Universe"
http://www.farmweb.au.com/h2o/h2universe.html

"Water in the Solar System"
http://www.farmweb.au.com/h2o/h2solar.html


"Life in the Universe" at Professor Stephen W. Hawking's web pages:
http://www.hawking.org.uk/lectures/life.html


"The Atmosphere (& Hydrosphere)" by Dr. Rick Behl:
http://seis.natsci.csulb.edu/rbehl/300i-L06.htm


"Volcanic Gases and the Origin of the Atmosphere":
http://volcano.und.edu/vwdocs/Gases/origin.html

-------------------------------------------------------

I hope that this helps in clarify this answer.


Best regards.
livioflores-ga

http://www.sciencedaily.com/releases/2004/06/040617081017.htm might
answer this question...

If we can assume that our science teachers have told us correctly that
comets are mostly ice.

For monroe22, what can possibly answer your question? Even if comets
provided the water for earth, that just moves the question to the
origin of the comets, doesn't it?

crythias-ga: You are absolutely correct. I suspect the origin of water
is a mystery which irritates scientists.
Thanks,
monroe22

livioflores-ga: One of the references you listed (www.gustavus) is so
grossly in error I am surprised that it was quoted. It states ferric
ion as the reduced state and ferrous ion as the oxidized state. High
school chemistry students know otherise.
Regards, monroe22

Monroe22,
In regards to your statement that outerspace seems not to contain
oxygen, please check this website:
http://www.cv.nrao.edu/~awootten/allmols.html

You will see a number of oxygen containing compounds which have been
detected in space.

livioflores: Many thanks for the voluminous additional research. It
answers after a fashion my curiosity about the origin of oxygen and
water. I say after a fashion because the theories of astrophysicists
(or speculations, as I prefer to call them) are impossible to refute
unless you are one of them, and who is?
My scientiic background in research is very low level compared to the
giant intellects residing in universities, e.g., Hawkins. Yet, there
is something which I find uncomfortable in their arcane theories of
what occurred billions of years ago. Something like the ancient
priesthood that hoodwinked the ignorant.
Regards, monroe22

I didn't read over the answers all that carfully, but they questioner
seems to want to know the astrophysical orgin of the oxygen itself,
and I didnt see in the responses anything about the C-N-O chain.
Oxygen is formed in stars by a fusion process. The CNO chain is the
second most common stellar process after the P-P chain which converts
H to He. So, thats where the oxygen comes from... stars. And, given
that its a fairly common and reactive element, you'd expect it to be
bound up in molecules pretty quickly.

nanoalchemist-ga:  C-N-O formation certainly is an explanation as a
source of oxygen. What puzzles me, as a non-astrophysicist, is how and
where primeval water was formed, how it got from there to Earth.
monroe22

I think that the answer is clear:
Hydrogen was formed short time after big bang.
Oxygen was formed in the first generation of huge stars, and probably
is still forming.
Supernova explosions send oxygen and other heavy elements to space and
form interstellar clouds.
You have oxygen and hydrogen (with a lot of other elements), put this
atoms or molecules together and you will get WATER!!
Next generation of stars (including our Sun) used these clouds (that
contains hydrogen, helium, carbon, oxygen, iron, water, etc, etc, etc)
to form itself.
This is the origin of our oxygen and water (and nitrogen, and iron,
and carbon, and uranium, etc.).
The rest of the story is in my answer, or just read the following
documents (links including in my answer):
"MSL111: Notes: The Origin of the Oceans"
http://www.sfos.uaf.edu/msl111/notes/origin.html

"Water in the Universe"
http://www.farmweb.au.com/h2o/h2universe.html

"Water in the Solar System"
http://www.farmweb.au.com/h2o/h2solar.html
 
Believe or not these newer is a personal decision, but if I cannot
believe that the water was formed in interstellar clouds, why I must
to believe that the Sun is mostly formed by hydrogen and helium.
If only one scientist tell me that, ok I can have a retional doubt,
but if almost them tell me the same...

Interesting thread.  The basic answer to your question has already
been answered, but it seems you are not looking for (or are not
comfortable with) a scientific explanation.  Anyhow, it seems that you
are basically asking why Earth has water--where did it come from. Much
of the comments have neglected the importance of the earth's position
in the solar system, it's tilt, and other environmental issues that
are significant--these factors all play a part in the emergence of
water on earth.

By the way, recent research on comets suggests that they are not
entirely cold and composed of ice, but are hot and flaming (after all,
they are flying through space at very high rates of speed).  You'd be
hot too! Just an interesting aside..check it out.

One small point in your original question / statement regarding
?incandescent aggregation of matter which eventually cools?. About a
century ago, Lord Kelvin determined the age of the Earth based upon
thermodynamic calculations. He arrived at 100 million years (though
others arrived at lower figures). It is of course somewhat older than
this, but he didn?t know about natural radiation. It is the power
source which keeps things hot, drives plate tectonics, causes
earthquakes, volcanoes and mountain building.

Best

In my opinion, nanoalchemist gave the best answer. The oxygen when
first formed was very hot and was likely the oxygen nucleus. Free
electons were also produced and made the shells of electrons for the
oxygen nuclii when they cooled below plasma temperatures. The abundent
hydrogen then combined chemically with the oxygen making water.
Smaller amounts of oxygen combined with carbon to make carbon dioxide,
carbon monoxide and many other oxygen compounds. Some of these
chemical reactions occured in the nebula, the disk that surounded our
proto sun and the reactions are still occuring in many locations
including our Earth. Photo synthesis is the main thing that made our
Earth different. Free oxygen is a byproduct of photosynthesis.
 I have not heard a good explantion of why the Sun and gas giant
planets got only trace amounts of the comparatively rare elements such
as oxygen.These heavy elements concentrated in the inner planets,
while water including the attached oxygen mostly went to the comets,
farther from the Sun than any of the planets. We don't know for sure,
but we presume other solar systems are specialized somewhat as ours
with the heavy elements in the inner planets.   Neil

neilzero and all others: I appreciate your inputs, but all, including
the learned dissertations from the leading scientists in cosmology, if
that is the right word, involve speculations, AKA guesses, about the
physics of billions of years ago. I have no objection to
speculations...I indulge in those everyday.
  My question is not answerable...which is why I posted it...it leads
to interesting thoughts. Anyway, I am puzzled by what is the mechanism
in which a ball of molten iron and silicon ( I think ) attracts water,
not to mention other volatiles. Couldn't be God, could it? God forbid.
By the way, I am an agnostic.
monroe22