Not even going to attempt the math,
But I'm guessing the number comet to bring water is: "one helluva lot of them". Still, the theory might explain the deuterium or at least some of it.
Data from Europe's comet-chasing Rosetta probe has cast further doubt on the theory Earth's oceans were seeded by icy space rocks pummeling our planet. In its ten-year game of catchup with Comet 67/P, the craft has been using its Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) to sample stuff flying off the …
Why is it that these bloody canned statements always leave out the obvious, like 'what's different about this test subject (the comet) and the premise we are trying to prove (4 billion years ago, comets like the test subject brought water to Earth). Most people would be stunned if the chemical composition (deuterium to H2O ratio) of this comet remained constant over its 4 billion year life! If there is an argument to say that the current chemical composition of this comet should be identical to what it was like 4 billion years ago, then STATE THAT in the report!
...the assumption that just because the earth was "too hot for water to exist in a liquid state", that all the water would therefore disappear completely from the planetary aggregation, and need replacing from some other source like comets. Assuming that the original matter from which the earth accreted did contain water (would that be the case?), then as the planet was (or became) too hot for that water to be liquid, the water would vapourise - but if the earth's mass was roughly the same as it is now, surely the vapour would simply have hung around in an atmosphere within the planet's gravity well, rather than disappearing off into space - just as water vapour stays within the gravity well now, because only hydrogen and helium are light enough to disappear off into the great black yonder.
And then when the planet cooled down again, the water vapour in the extended atmosphere would have condensed into liquid on the surface, and formed the oceans.
Any astro-boffins out there care to explain why this shoudn't be the case? Genuinely interested...
Related point: don't terrestrial lavas have fairly quantities of water and other volatiles, up to several percent? As I understand it, water significantly affects the violence of a volcanic eruption, with more water in the lava causing more violent explosions, and water is the primary component of volcanic gases.
That implies (to me) that water can survive and be trapped in very hot, forming planetismals (sp).
When the Russians drilled why worlds deepest well at Kola Peninsula they discovered water at +40,000 feet deep at +350F temperature and 2500 Pa. The only explanation is that water is a fission byproduct, of either elemental Hydrogen and Oxygen, or the outgased H2 & O2 from fission vaporized rocks in the mantle. Like all of the Inert Gases that cannot form natural Earth compounds and can only be from elemental origins. Helium has a Specific Heat of 0.6 and Radon has a half life of 3.8 days. For any of these to exist after four billion years, they must be in constant production, so to is water. For more info see....
"Earth's Missing Geothermal Flux" at the FauxScienceSlayer site. Find and share Truth.
The extraterrestrial sample size is very small.
There are a number of other bodies in the solar system that have water in one form or another. It will be interesting to find out how the water that is eventually found on the Moon, Mars and so on compares with the Earth's and this comet (assuming it is in fact discovered and surveyed, of course).
Allthough it seems te be a lot, the complete amount of water on earth is less than what minor planet Ceres or Jupiter moon Europe holds.
I think it was here all the time, in some form, either bound or free. I can live with the assumption that our infant cooking earth was covered with a thick, damp, cosey water blanket.
Everything agglomerates one way or another when you are sweeping up a primordial disk of dust and gasses. Once 'separated out' into "bands" the agglomerates are still not well-behaved, they still keep on bashing into each other and slipping into each others backyard.
If near Oort objects fall sunward obliquely they are quite likely to end up orbiting in the Kuiper belt for a while before being hit on by something else in the crowd and so be shoved further inward. Not to mention that they are so slushy that they probably have been exchanging bodily fluids for a few hundred million years while there and are quite mixed up by the time they get picked up and get a going over by Rosetta and her future decendants.
Surely, isotope ratios must depend upon specific histories of specific objects, especially in a system that is driven by nuclear interactions and characterised by large but varying distances and over an immense period of time. Oort may not be representative of the original solar disk that condensed out the sun and all the other bits. It seems reasonable, given planetary composition variance with distnace from the sun, that it is a distillation of the lighter elements and compounds thereof. Kuiper less so, and so on back in toward us rocks sitting in the sun's highly irradiated atmosphere. Other objects even further out than us are not protected as well from alot of that irradiation. What do we know of how that effects all the assumptions the good doctor from Rosetta? Just because we have no data doesn't make a factor a negligible given. BTW: my STATS01 course suggested that a minimum decent sample size for saying anything about a population is at least 40. The sample of 12 referred to reminds me of a typical macro economic model built upon a set of 12 years of National Accounts (anything longer and the behavioiral game has changed for sure!) accepted used by gullible polticians to justify a major policy shift demanded by their commercial sponsors. :-)
Lets not allow cosmology and space science become another 'dismal science' for want of thinking a bit more deeply before adding to misguided premature debates about things being this way or that way when we are still in the data collection phase.... journalistic demands for 'statements' and desires for '15 minutes of fame' not withstanding.
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