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back to article Water like that of Earth's oceans found in comet

Ice found in a comet supports the theory that the earth's oceans were delivered to the planet in the form of crashing comets. It is thought that the Earth's oceans formed about 8 million years after the planet did, and scientists have long suggested comets as a cause. Many comets contain ice - unlike asteroids which are largely …

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Hmmmm

The D/H ratio is surely limited to a certain band of values and is hardly a signature like a DNA test. If that's the best evidence the theory has then it's a bit thin. Skits about ducks and witches are more convincing.

Filling the earth's oceans would need a whopping great comet or a few smaller - but still massive - ones or some millions of Hartley 2-sized comets. Hartleys 2 is not enough to fill 10x10km of the oceans.

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Anonymous Coward

also

Where did the comet's get their water from?

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Anonymous Coward

God of course. Day 2.

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Boffin

@Also

The hydrogen originated in the early stages of the universe after the big bang, and the oxygen (and most of the heavier hdrogen isotope deuterium) was produced by stellar nucleosynthesis in previous generations of stars, just like everything else in the Solar system heavier than helium (most of that too) and lighter than cobalt.

Heavier elements would have been produced by supernovae and more exotic objects, like quasars.

http://en.wikipedia.org/wiki/Stellar_nucleosynthesis

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Alien

From Water

"For they deliberately overlook this fact, that the heavens existed long ago, and the earth was formed out of water and through water by the word of God," 2 Peter 3:5

So, since the Earth was formed from water, so was everything else.

Incidentally, has anyone else noticed the correlation between the lack of evidence required to declare mobile phones a health hazard and the lack of evidence for Evolution?

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FAIL

What?

Lack of evidence to declare mobile phones a health hazard = why they haven't been.

If you think there's no evidence for evolution, you're wilfully ignoring it.

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FAIL

Time to put your head back up your ar$e.

Please keep the religious bullcrap to yourself.

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Alien

Evidence?

"If you think there's no evidence for evolution, you're wilfully ignoring it."

I often ask for some but all they give me is the interpretation of evidence.

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Dear Mr AudiGuy

Please try and keep your intolerance to yourself.

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FAIL

Sorry Sparky...

...can't do that.

Too any religious nut-jobs on the planet with nothing between their ears but Jello. ALL a very dangerous lot.

Seems like you might fit that category. Hmmm.

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Anonymous Coward

It is complex

but yes, water on this planet did come from off planet. it is hard to have water on a hot coalescing sphere that is cooling over time. Now, the problem. The existing water is being leached into space and has been for a long time from solar winds. We will need another comet rain at some point or the planet will end up like Mars. Scientists talk about how the earth will eventually meet a dismal end when the corona of the sun engulfs the planet. That is wrong, the Earth will become uninhabitable when the Sun's corona moves just a little closer to earth. "Death" may happen sooner if the Sun experiences increased amounts of coronal activity with huge ejections becoming the norm. This is serious stuff and the makings for quite a panic if everybody understood exactly what is going on. There is no question that we are doomed, the question is when? It is best to keep oneself busy praying so that the inevitable doesn't happen. There is no cosmic cavalry to come to the rescue and the truth is bleak shit, so deal with it.

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Anonymous Coward

"It is best to keep oneself busy praying..."

I was with you up to that point

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"quite a panic"

Seeing as cosmological events occur on a scale of hundreds of thousands of years, I hardly see the need for any panic yet....

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>"It is best to keep oneself busy praying..."

>I was with you up to that point

Even if I believed in God (which I don't) I wouldn't be praying to him. At least not in the traditional sense. I'd be berating him. Being under threat of species extinction is not something you thank God for.

For get "Oh thank you Lord for taking little Annie into your arms..blah..blah".

Instead try "Look for fucked up supreme being why the hell couldn't you get your head out of your arse and save my little girl?"

If Gods exist then it's high time we took the fight to them. No more Mr. Meek Guy :D

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Meh

Meh

Frankly with all of the ever present threats we get told about on a daily basis (Planet Destroying Asteroid, Super Volcano, Earths Magnetic Field Switching, Godzilla, Zombie Apocalypse, Khaaaaaan….) if I worried about the sun expanding and wiping us all from the face of the planet along with everything else I wouldn’t have time to do anything but cower in a foetal position and cry myself to sleep on a daily basis.

Frankly I’m much more likely to get killed driving to work and yet I still do that everyday, mores the pity.

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Go

@AndrueC

Hi, I remember you from Wednesday 7th September when you commented that "If you want to be rude and offensive then Prof. Dawkins is usually the man for the job. NB:I'm an atheist but I don't like his attitude."

Now, with your "No more Mr. Meek Guy" approach, you're taking the fight to God in a way that Dawkins would be proud of. Have you had a "road to Damascus" conversion in the last month? :-)

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Childcatcher

Since God doesn't exist I don't worry about offending him :)

It's a valid point though. In a discussion forum like this I wouldn't criticise Prof Dawkins' posts should he make any. My objection isn't about /what/ he says - it's /who/ he says it to. I've been contributing here long enough to know that we're a right bunch of bastards and all the weaklings have long been weeded out. If I cause offence to anyone they are quite capable of returning the favour.

No the problem I have with Prof Dawkins is that he seems to enjoy attacking people that didn't ask for it and challenging the core beliefs of people who are weak minded. That seems cruel to me. Funny...but cruel.

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Anonymous Coward

Numbers?

So how many comets does it take to fill the earth's oceans? Is it reasonable to expect that many dropping on earth in a mere eight million years? It seems a bit steep to me but then I didn't throw this idea out in the ocean. It does pose the question though, why aren't we drowning now in all that extra water that's come down in the last couple milliard years? Or why did it stop raining comets after the first couple million? Inquiring commentards want to know.

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Boffin

re: Numbers?

Why did it stop raining comets? Because they either all settled into independent orbits, retreated to the Oort cloud, or hit the planets (having been dragged in by their gravity wells).

See the "Late Heavy Bombardment" theory(s) for details.

PS nice pun on the "raining" comets.. :-)

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Anonymous Coward

So... How many do we have to steer into Mars to make it habitable?

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Boffin

@Numbers?

Current theory is that most of the water arrived on Earth during a period known as 'the late heavy bombardment' around 4 billion years ago and lasting about a quarter of a billion years.

Recent models of solar-system formation suggest that interactions between the planets in our solar system, and another gas giant planet led to this other panet being ejected from the solar system and the remaining planets ending up where they are now (it is thought that Jupiter originally formed much closer to the Sun).

In this process, the Oort cloud and Kuiper belt would have been perturbed, resulting in a large number of comets and asteroids entering the inner solar system. The results of this can be seen on the surface of the Moon, where most of the craters originate from this period. In this process, a large amount of rock and ice would have arrived on Earth and the other inner planets. The Moon, and Mercury are too small to have held onto the water vapour that would have resulted, but the Earth and Venus are not.

This also explains the abundance of some of the other elements in the Earth's crust, which are more abundant than theory predicts they would be in this region of the Solar System, or which are very dense and would have ended up in the Earth's core during its formation but which are abundant in asteroids, etc. Gold is a good example.

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Alien

Habitable?

But water is toxic to the native Martians!

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So our solar system was originally like many other recently discovered

solar systems with a gas giant close to the star. What caused the disruption

that ejected the gas giant and re-arranged the solar system in its present

life-friendly form? Was it a likely event or something rare and improbable?

I suppose the most likely cause was another star passing close to the solar

system, I've no idea how likely this would be but I imagine most such close

encounters would not result in re-arranging the solar system into a life

friendly form. It is remarkable that after the disruption the solar system

settled into nice stable nearly circular orbits. It also suggests that the inner

planets were not necessarily formed at their current distance from the sun.

Coupled with the need for the "late heavy bombardment" to fill Earth's oceans

the "rare Earth" point of view looks even more convincing.

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Pint

Wow

The world was created by comets and asteroids and space junk. Who would have thought of such a possibility. Nice we have some confirmation to such a new and novel thinking.

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That would be...

...wet and salty?

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Boffin

nope

It's got condoms, carrier bags and oily seabirds in it.

Not even the planet it came from could get rid of the stuff.

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Anonymous Coward

Water?

Why can't comets bring vodka or whisky?

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Windows

Just as long as it is not rum.

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So

How many billion years before the sea covers Everest ?

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Anonymous Coward

...

you mean theres another type of water??

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Angel

The sky is falling, the sky is falling?

So what about the carbon too? If that also came from above (God does love us after all) then it's a short step from there to happiness in the form of C2H5OH

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Alien

Darn alien flesh taste so good, wonder what other alien life we can find in the oceans??

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Joke

What would be really great...

Is if someone dug a discarded a 4 billion year-old bottle of Evian or Aquafina :)

Those bottles last forever in landfills you know.......

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Devil

Duh!

Getting tired of these blindingly obvious "xxx substance arrived at earth on comets/meteorites" articles.

According to my understanding of planet formation, planets form by clumping and collisions from meteorites and comets, so ALL elements heavier than gas arrived that way.

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Ye-es but collisions create heat so the idea of water arriving at the same time as everything else is dubious. It's generally accepted that water must have been one of the later elements to arrive because it needed everything else to have cooled down first otherwise it turns to steam and is blown away by the solar wind.

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@ needing a big comet...

There's more fresh water on Ceres (the largest asteroid) than in the earth's oceans.

The saltiness is leached from rocks - and current ocean salinity is quite a bit higher than it was a couple of billion years ago.

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Just like the Bible says...

God made the expanse [firmament or atmosphere?], and separated the waters which were below the expanse from the waters which were above the expanse; and it was so. Gen 1:7

So, I'm not surprised there is water in space with the same isotopic signature.

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Mushroom

You had me until 'Just like the Bible says'.

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Coat

Considering...

when the story started to be told and what limited scientific knowledge was available then it is not a bad potted history of the arrival of man on earth. Shame about the God bit but how would you explain it to someone of limited knowledge and language skills if you also didn't have a full understanding of it yourself.

You have to remember we are still making up theories about how it all started and then proving or disproving them, within the limits of our knowledge. Try explaining the finer points of string theory to a 3 year old and see how you get on. Come to that try explaining it to me.

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Meh

I think it's a joke -- or a nice, shiny troll -- read a bit more carefully, there's a clue in there.

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WTF?

Everyone knows that yoyos have strings and that wingnuts are the ones with little "ears" to turn them with.

So, I'm not surprised that there are sausages in Tescos.

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@Cynical git

"when the story started to be told and what limited scientific knowledge was available then it is not a bad potted history of the arrival of man on earth."

Much in the same way that I can see shapes in the clouds. It's rather easy to take a poetic story and make it fit if you use metaphors. Besides, the sequence of events is largely logical.

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Anonymous Coward

@AndrueC

Yawn..... You've lost me.

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Joke

Tosh!

So 6000 years ago, and on the 3rd day a stonking huge comet hit the newly made earth and created the oceans?

See title.

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Angel

Tish!

Well that one is obvious, ain't it?

We know that humans cultivated bananas some 10000 years ago. Why would they do that if God had not promised them there'd be water 4000 years (and three days) later?

Halleluja. (or amen or whatever they use as linebreaks)

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Happy

Ah-

Halleluja = LF

Amen = CR

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Duh!

the earth came from the sky too!

I dare say some of our water came from comets but a lot of rocks contain things called oxygen and hydrogen which are all that’s necessary to make water.

We can only guess at how fast the earth grew and, while it might have been too hot for surface water for 8 million years it doesn’t mean that any accumulated water vapour was blasted into space - venus could make a pretty puddle if it cooled a bit.

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Boffin

Sadly...

...the reason that a lot of rocks contain so much water and oxygen is that they have been produced by the reaction between oceanic basalt and water in subduction zones. This is how continents formed, since the resulting granite is less dense than basalt so tends to 'float' on it. This is why the continental shelf has a sharp drop-off. Evidence would seem to sugest that the thermodynamically favoured reaction is between basalt and water to produce granite, and not the other way around. So yes, all you need are hydrogen and oxygen to make water, but rocks are rocks, not hydrogen and oxygen. The oceans are actually being slowly consumed by such reactions, not the other way around.

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Anonymous Coward

No it won't, you are all figments of my imagination. I won't let it happen to you

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Joke

If we're figments of your imagination you must be really sick :)

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