What caused the water to apear on Earth?

That's nice. I BELIEVE it's the droppings from undiscovered intergalactic space cows.

 

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There are a few hypotheses as to where the water on earth came from. We can speculate it came from somewhere else in the form of comets, but that doesn't explain where the water originally came from.

We can also speculate it came from earth itself.

When the earth was cooling, water vapor formed and condensed, clouds formed and for millions of years, continued to rain until the earth was an ocean planet.

 

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An alternative theory to earth's origin has proto-earth as a large gas-giant planet, similar to Jupiter only smaller. It had a rocky/metallic inner core [like Jupiter], surrounded by a thick blanket of gas [like Jupiter]. The inner core formed when the early gases cooled to below the boiling point of the solids/metals and they rained out from the gas-ball giant, forming an inner liquid rocky/metallic core, which gravitationally differentiated into our present-day stratification.

The gas blanket was mostly hydrogen/helium [H/He], but other gases as well, including the much heavier H2O, which settled below the H/He outer blanket.

Under this theory, other stars formed in the vicinity of our Sun, in a "stellar nursery" like we nowadays see elsewhere in our galaxy. These were hot OB stars, much closer to our sun than they are nowadays, and they eventually boiled away [at about 1 foot/year of depth for a half billion years] the H/He blanket on proto-earth, leaving behind the much heavier H20. On Jupiter and Saturn, much of the original H/He blanket boiled away, but not all, leaving a distorted H-1/H-2 ratio. Likewise the murky interstellar clouds were driven off by the intense UV of the OB stars, and those stars eventually drifted away from our Sun, leaving us in our current condition.

One of the advantages of this theory is that it posits the formation of the moon along with earth from the same proto-cloud that gave rise to proton-earth, with a resultant moon in orbit about earth as the same orbital plane about the sun; a difficulty with the old planetoid striking earth and ejecting the moon idea. While the kinetics are difficult to explain in a short treatise, such a formation would also generate an enrichment in proto-earth of the heavier elements, and a deficiency in the moon. Thus, one would expect the moon to have relatively much less iron/nickel than earth, compared to the lighter elements [Aluminum, Oxygen, Silicon].

Thus, under this theory, the water has always been here since formation of proto-earth; no need to invoke comets striking the earth [which seems to be far too little, anyway].

 

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The Earths formation is fairly well charted.

"abundances of elements in Lunar and Terrestrial material are sufficiently different to make it unlikely that the Moon formed directly from the Earth"
http://csep10.phys.utk.edu/astr161/lect/moon/moon_formation.html

The best theory is that a mars sized planet collided with eh the protaearth to form the moon.
The early solar system could have had as many as a 100 planets; most of which were expelled from the proto solar system.

The sun could well have formed in a stellar nursery and there is evidence that the solar system may have experienced the shockwaves of a supernova. The solar wind would have forced the lighter materials outwards. But even by that date the solar disk and protoplanets would have already formed. So it is possible that the water, and a thick atmosphere, was formed from out-gassings on the early molten earth.

But it should be said that the evidence from the number of impact scars on places like the moon show that the transportation of water by comets and asteroids is possible and sufficient to provide at least a good proportion of the Earths water.

 

Traces could be left by whatever what about real presence of ice its found anywhere else than europa?

Yes same question, if it comes from comets how it gets on them, what are comets/asteroids/meteors?

 

How much water (ice) moon has comparing to earth e.g. earth has 50% of surface filled with water, what about moon?

How long does moon exists?

Moon does not have atmosphere is it? It ever had one? What are other planets that dont have it?

 

There is very little left but there will be deposits near the poles and primordial gas trapped within the moon.

The moon is near enough the same age as the Earth.

The moon may have had a atmosphere for a very brief period after the late heavy bombardment stage (say 3.9 billion years ago); however it would have been lost very quickly; almost as quickly as it formed. It would be interesting to look for evidence to see if any `seas` could have briefly formed. Today the moon retains a very, very, thin atmosphere; (the main reason why the moon lost it`s atmosphere is because of the moons low mass and lack of a magnetic field).

 

[/QUOTE]Today the moon retains a very, very, thin atmosphere

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No. The moon has ZERO atmosphere - it's a vacuum as good as the vacuum between the planets.

Yes, the moon is distinctly different from the Earth in relative abundance of the elements - being relatively enriched in the lighter elements compared to the heavier. While some have suggested that implies a goodly portion of earth's "mantle" material was ejected [by planetoid impact] and then re-formed into a sphere, and underwent subsequent stratification, there is no plausible mechanism for such, and the likelihood of this occuring in the same plane as the earth's orbit about the sun is remote.

Conversely, if there were two centers of gravitational concentration orbiting about each other in the proto-cloud of hot gases that would have given rise to our earth/moon system, advanced dynamics suggests that the more massive one would become enriched in the heavier elements, while they were still in the gaseous phase. After they cooled to boiling and rained out, there would be no more intermingling of the materials between the two, and two separate planets would have been borne in orbit about each other, each having a thick sea of hot liquid H/He surrounding their liquid inner cores. The less massive one would have been relatively depleted in Iron/Nickel and the heavier elements, compared to the lighter Al, Si, etc., in which they would have been relatively enriched. While the lighter one [moon] would eventually have all of its H/He and other gases volatilized, leaving it airless, the heavier one [earth] would have lost all of its H/He, but some, if not most, of the heavier gases would have remained behind [H2O, SO2, CO2, NH3, etc.], though most would have reacted with other materials to form solids. Much of those gases would also have been entrained during the 'rain-out' phase of the liquid Fe/Ni and liquid Si/Al/O, where they still remain in the mantle region, though outgassing during volcanic eruptions.

 

superluminal. Water has been found on ONE planet 150 light years away. I know there are clouds of water ice crystals in space but of no use to us as they are far too rarified.

I mentioned a few places in the solar system in passing. There is no need to use your normal PIG manners to try and score points on the matter. I did not say there was none elsewhere. Certainly there is water on comets, if you don't mind some cyanide and such mixed in.

So if water is everywhere, show where it is on Mercury? Or maybe the gas giants where ammonia would instantly soak up all traces of water and so make it useless. Or how about Venus at near 400.C . Where's the water you say is everywhere? Perhaps you'd like to list those dozens of worlds since I don't know about them?

Go back to sleep. You're a waste of space.

 

kaneda,

What you are personally ignorant of is not important, kaneda. Every planet, and many moons, in our solar system contains at least small amounts of water in one form or another. Venus is thought to contain very little at the present time in its evolution, as almost all has been lost as hydrogen due to its high heat. As a counter example, the scientific consensus is that there is a liquid ocean under the icy crust of the moon Europa, a huge amount of water.

Water has only been verified on one extra-solar planet, but it is thought to exist on most of the discovered worlds as a vapor. The problem is that most of those newly discovered planets are very distant from us and close to their parent stars, making accurate analysis of their spectrums for water vapor very difficult.

 

i believe you are not aware of all the facts.

"The Moon has an atmosphere, but it is very tenuous.
Gases in the lunar atmosphere are easily lost to space. Because of the Moon's low gravity, light atoms such as helium receive enough energy from solar heating so that they escape in just a few hours."

Read more

"Composition of the tenuous lunar atmosphere is poorly known and variable,
these are estimates of the upper limits of the nighttime ambient atmosphere
composition. Daytime levels were difficult to measure due to heating and
outgassing of Apollo surface experiments."

Read more

 

Hum,
a nice article to bring people up to flank speed...

Read more

(Summery for lazy people - `could be primordial or asteroids or both; we don't know for sure`)

 

Blobrana:

I stand technically corrected.

It depends upon one's definition of an "atmosphere", I suppose.

On the moon, of course, there will be a continuous infusion of solar-wind particles, as well as some releases of atoms from the surface with the impact of micrometeorites, etc. Even tiny "cometoids" might bring in frozen gases.

Once delivered to the moon, those gasses will then escape. The "atmosphere" would be the 'steady-state' amount determined by the infusion rate, and escape rate.

I suspect that the methane molecules that were detected were from such "cometoids", and not from out-gassing from the moon's interior.

In any event, one could also say that there is an "atmosphere" between the earth and the moon, since with adequate instrumentation one would almost certainly detect some atoms of gasses.

However, the moon's gravitational well would apparently keep the concentration slightly higher near the moon's surface, and thus technically one might refer to that as an "atmosphere"

Nice links, thanks.

 

Some people believe that God put the water here. :shrug:

 

Hum,

"Earth-Asteroid Collision Formed Moon Later Than Thought
The moon was formed from fragments of Earth after a collision with a giant asteroid relatively late in our planet's formation, new tests of moon rocks show.
The finding upends many of the prior theories for how the moon came to be, researchers say."

Read more

 

Interesting. It looks almost like they are coming around to the idea that the earth-moon system continued to exchange material for quite some time [which under the theory I referenced above, accounts for an enrichment in the earth of the heavier elements]. They talk about exchange of material in the gaseous phase between both earth and moon - exactly the idea discussed by me earlier.

As they think about it more, they'll likely discard the need for an asteroid impact to eject the material, and instead recognize that if the earth-moon system formed like Jupiter and other gaseous planets, then the hot molten materials of the earth's interior were once slightly hotter, and in the gaseous phase, until they rained out forming a liquid ball in the interior of a dense [approximate density of 1.0] ball of hot liquid H/He.

You should do them a favor, and forward this link, as well as previous Sciforum postings of mine on the earth-moon formation, so they would have the benefit of this insight.

 

That was the explanation I read decades ago and I still see nothing wrong with it. The solar system is believed to have had a cold formation (ie: The sun did not ignite till later) which would have allowed light gases to form and mix near the centre of the solar system. When the sun ignited, the hard UV, charged particles, etc could have mixed the hydrogen and oxygen to form water.

 

Walter LW. The Earth-Moon system is thought to have formed around four billion years ago, so quite late. The impact would have meant a change of materials with gases and vapours/liquids mainly being pulled in by the more massive Earth.

The solar system is believed to have had a cold formation which explains the presence of lots of light gases close in to the sun. Internal planetary heat would have come later, through pressure of materials.

 

2inquisitive or is it 2rude? Someone made a statement to me which I believed was doubtful so I asked him to back it up. That is where you butted in with your irrelevances.

Water on Venus is where?

Europa is not a world but a moon. I would have thought that even you might have known this but:shrug:

I am of course aware of the problem with extrasolar planets as I think every other person on this board is.

 

Err... so?

And I beg to differ. It may not be a planet, but it certainly is a world.