Posibly duplicate from Water on Mars and Earth

I remember well a hydrology course where our teacher made some calculations of the total flux of water from Mantle ejections in Earth's history. He said the result gives you the total amount of water presently in the oceans.

Then I started to hear theories about water coming from meteorites, and I wonder how much water has truly come from each source?

  • $\begingroup$ I think I get what you're asking well. But really not sure what "has sloped while degassing" is supposed to be. Can you try different wording perhaps to help us understand better? :-) $\endgroup$ May 29, 2018 at 0:04
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    $\begingroup$ The word migth be flux? The teacher told us as mantle looses water because of geological proccess something like 1 million hectometer year x 4.500 my gives the amount of present ocean. $\endgroup$
    – user12525
    May 29, 2018 at 0:17
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    $\begingroup$ Related, if not a duplicate: Water on Mars and Earth. This question has also been asked at the Astronomy.SE sister site: How did water get on Earth. $\endgroup$ May 29, 2018 at 18:06
  • $\begingroup$ The marcked answer is also valide here and the question is similar. $\endgroup$
    – user12525
    May 29, 2018 at 18:31
  • $\begingroup$ @DavidHammen I don't see the Mars question as really helping with this one... it goes into very limited detail suggesting it's a debate that goes back and forth. Is that all there is to it? Even if so, detail/sources/etc would answer this direct question better. $\endgroup$ May 31, 2018 at 2:01

1 Answer 1


The answer of this post clarifies also this related question: Water on Mars and Earth

If water on Earth came from meteorites, why doesn't Mars have substantial water?

First off, that's a conjecture regarding the origin of the Earth's water rather than a known fact. A few times a year or so, a new journal article will appear that argues that the Earth's water is primordial, then another arguing that it came from comets, then yet another arguing that it came from asteroids.

If the Earth's water is mostly primordial, most of it is over 4.5 billion years old. If it came from asteroids or comets that collided with the Earth after the Earth had formed, it's still very, very old. Regardless of the source, almost all of the Earth's water has been here for at least 3.8 billion years old, since the end of the late heavy bombardment.

Mars and Earth are both rocky planets. If the water was there, at Mars or at the Earth on Archaic, then I guess degassing of Mantle was more quick than I thougth and what my hydrology teacher told us had not a lot of sense. "Regardless of the source", so then water came from both sources but probably meteorites are not the main source.


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