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Rosetta Results: Comets "Did Not Bring Water To Earth"
An anonymous reader writes with findings from the Rosetta mission which suggests water on Earth probably came from asteroids, and not comets."Scientists have dealt a blow to the theory that most water on Earth came from comets. Results from Europe's Rosetta mission, which made history by landing on Comet 67P in November, shows the water on the icy mass is unlike that on our planet. The results are published in the journal Science. The authors conclude it is more likely that the water came from asteroids, but other scientists say more data is needed before comets can be ruled out."
They got it wrong. The dry comets are lighter and so are still flying around. The wet ones were heavier and so fell to Earth.
I should use this sig to advertise my book ISBN-13 : 978-1501515132.
Didn't planet earth come from 'asteroids'?
“He’s not deformed, he’s just drunk!”
Why does the water have to have come from comet/asteroid/whatever impacts? Maybe it just kind of seeped out of rocks or something. Hydrogen and oxygen are pretty common.
The more informative article from the ESA website says that the Deuterium/Hydrogen (D/H) isotope ratio is significantly higher (more than three times, in fact) than that of water found on Earth.
However, The comet in question is not of the same type and composition as *all* comets. In fact, comets (even those that generally share orbits with the one sampled) vary widely in their D/H ratios. As such, the paper does not claim that comets didn't bring water to Earth, merely that comets like the one sampled (comet 67P/Churyumov–Gerasimenko) by ROSINA did not bring water to Earth.
From the better TFA:
No, no, you're not thinking; you're just being logical. --Niels Bohr
surely the Earth has hit by so many objects with varying D/H that the D/H of each object is not important to tell us the source of water, but rather tells us of the formation environment of the object itself. I don't see how anyone could claim that such D/H comets could not seed earth. i just see a larger D/H range of the seeders.
Water is pretty heavy. The collision would certainly have vapourised all water on the surface and underneath and even converted a lot of it to H2 + O2 , but the rest would simply have hung around in orbit as ice and rained back down eventually.
The press release should have said: The comet is dry as bone, Earth water must have come from somewhere else.
So far no water ice has been found and the pictures shows a completely dry hard rock. That they keep calling it an "Ice mountain" is just crazy. There is no proof that there is ice on a comet. Only that there is hydroxyl in the coma. Saying "We know of no other way for there to be hydroxyl in the coma without there being ice in the comet" is just bad science. Especially when there have been lab experiments showing how hydroxyl can be created from silica rock hit by protons (solar wind)
Deuterium/Hydrogen (D/H) isotope ratio is significantly higher (more than three times, in fact) than that of water found on Earth.
Q: How do you separate heavy water from light water?
A: Distillation. Light water boils off / evaporates more easily, because the molecules are lighter, and leaves the heavier water behind.
Why shouldn't this be true of vacuum sublimation as well?
Leave a chunk of dirty ice orbiting the sun in a hard vaccuum for a few million years, with the water quietly sublimating away. Seems to me the result would be that last remaining chunk of dirty ice would have a substantially larger fraction of heavy water molecules than the water on the planet where the deep gravity well hangs on to the lighter molecules.
Is it enough to explain a 3:1 enrichment? No clue. But I'd like to see that the analysis was done and what the scientists' estimates were.
(Not to say they ignored it. The last time I raised a similar question about a scientific paper reported here it turned out that the scientists HAD examined the issue.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Previous measurements of the deuterium/hydrogen (D/H) ratio in other comets have shown a wide range of values. Of the 11 comets for which measurements have been made, it is only the Jupiter-family Comet 103P/Hartley 2 that was found to match the composition of Earth’s water, in observations made by ESA’s Herschel mission in 2011.
Is it just my observation, or are there way too many stupid people in the world?
you'll see they have pretty solid evidence that this particular type of comet (Jupiter family) had a deuterium/hydrogen ratio in water that is very different from earth, whereas many asteroids (chondrites) have about the same D/H ratio. All they were saying was that this type of comet was not responsible for delivering most of earth's water, which seems reasonable based on their evidence (see figure 3 from the article).
A brain is a terrible thing to waste... Mind? That's debatable.
it tastes funny.
Do not look at laser with remaining good eye.
There seems to be a lot of confusion and conjecture in the comments about the grandiosity of the claim. This does not necessarily rule out all comets. Maybe an attempt at a better summary of the article would be helpful:
Background:
- Not all water is the same. Some water is heavier due to a presence of a certain amount of deuterium.
The general consensus is:
- When the solar system formed, the components for water were created.
- These components eventually formed with the early Earth and a water cycle was created.
- Yes, the early Earth was hot, but heat and elements were plentiful and Earth managed to hold onto some of these elements and would have had water evaporating and raining back down again.
- The planet Theia *collided* into the Earth. A certain amount of the debris coalesced into the moon. Imagine Pluto smashing into your house.
- The heat from the collision would have evaporated/released all elements lighter than X, which includes water. (ed: perhaps water on the moon is more closely related to early earth water coalesced and re-condensed?)
- Sometime later, the Earth received much more water than would have been sustained from such an impact.
- The weight (deuterium ppm) of this "new" water is different (much lighter) than the weight of "old" water, and generally any other water in the solar system.
So where did this "new" water come from?
This article suggests:
"We have light water in some comets and very heavy water in other comets. We have to assume the mixture of all these comets is something that is heavier than what we have on Earth, so this probably rules out Kuiper Belt comets as the source of terrestrial water."
And I believe this means:
It would have taken many of these Kuiper Belt comets to contribute a great deal of water to the Earth. If we use probe measurements to confirm other measurements and calculate the *average* weight of water on a number of Kuiper Belt comets (along the order of magnitude necessary be a main source of "new" water for the Earth), then we see that the amount of deuterium in Earth's water would have been much greater -- i.e. the water would contain an average weight of all impacts needed to saturate.
Thus this rules out Kuiper Belt comets being the main source of "new" water for Earth. Their water in general is simply too heavy on average. As soon as enough Kuiper Belt comets impact the Earth to come close to the amount of water needed, the calculations show that the level of deuterium would be much, much higher than what we see.
And the article itself turns to conjecture with:
So where do we look for lighter water? Maybe asteroids?
... and... where did the asteroid get the water? Smaller asteroids?
Without doing any research on the topic, yet smug in my own opinion (hello slashdot family!) I don't know why we'd ascribe a smaller rock-like mass as responsible for delivering simple molecules to a bigger rock-like mass.
Everybody knows water comes from rain.
But seriously, there is a giant body close to earth, that is chock full of hydrogen, and if you burn off that hydrogen by oxidation you get water.
If we also can get carbon into play, we have most of the ingredient in the cycle f life
-- Another senseless waste of fine bytes.
You're not wrong about water being H2O, the difference is in the H part. Hydrogen is one proton orbited by one electron (an oversimplification, but work with me here). An isotope of hydrogen called "deuterium" also has a neutron in its nucleus. So, both deuterium and protium (the "normal" isotope of hydrogen, without the extra neutron) are hydrogen, but deuterium has more mass due to the neutron. Water can be formed with either isotope; water formed from deuterium and oxygen is sometimes called "heavy water".
Now what they're looking at here is the ratio of ordinary water to heavy water naturally occurring in a given environment. Here, they've determined that the ratio on the comet is not the same as what's commonly found on Earth. They've therefore put forward the hypothesis that the current thinking about the origin of water on this planet may be wrong, because this particular comet's ratio is different, and the assumption is that most comets are composed of similar material.
Never underestimate the power of stupid people in large groups.
My point was that there has never been any proper proof of there being either water or heavy hater on comets only hydroxyl (OH) in the coma. There are several ways the hydroxyl could have gotten there, so you cant say there has to be water in the comet core for there to be hydroxyl in the coma.
To be more specific, they speculate the water on Earth did not come from Comet 67P. Instrumentation showed evidence that Comet 67P is not on Earth and has never been on Earth.
A independent panel of scientists is reviewing the data.
The world is made by those who show up for the job.
I find it much more plausible that our oceans were derived from internal water than that asteroids deposited it. I mean, really, how much water could your average meteor deposit? Looking at the amount of water on our planet's surface, we would have to assume a long, horrendous bombardment. Asteroid material would then account for a large percentage of the earth's crust, and I don't hear anyone suggesting that.
And don't get me started on that whole "Theia" hypothesis. The only evidence for a planetary impact is the fact that we have a moon, and it's larger than one would expect. Very weak argument.
A sample of one is not enough to say one way or the other ont his matter.
Anything is possible. Even time travel into the past (with certain limitations).
No, Time travel to the past isn't possible at all. That would be acting like there is a physical place called the past to travel to which is physically separate from all the moving mass in the universe that we call the Present. That would require constant instantaneous non-big-bang creation of all the mass in the universe over and over again at a Planck-time like interval.. Care to show evidence for that actually happening?
It doesn't matter how some scientists choose to interpret certain equations, they are clearly misinterpreting how they actually relate to reality.
Actually, people a lot smarter than you have posited that it is, in fact, possible. It's quite unlikely, and completely beyond our abilities, but not impossible. Note that I said "possible" not feasible.
No, no, you're not thinking; you're just being logical. --Niels Bohr
They only thing they can say is that the water didn't come from Comet 67/P. They look at the ratio of Hydrogen to Deuterium in the water on the comet and compare that ratio to what we find on Earth. The problem is, we find comets with similar ratios, and comets with nothing like it. It seems we still have a long way to go in understanding how comets formed and what that says about where/when they formed. Comets may still have delivered the water to Earth, but none of them may exist any more to study. Rosetta didn't really answer a question here, it just gave us yet another hint that comets are not all created equally and we have a lot more studying of them to do.
So, we have one comet as sample.
That comet is aons old.
At some point in time "young" comets where supposed to seed the earth with water.
How can that single "old" comet prove that "young" comets did not do that?
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
This automagically means that all comets are out of the picture?
This seems very short sighted.
We need a sample of comets in the vicinity that likely existed in the time of our Earth's formation.
- Zav - Imagine a Beowulf cluster of insensitive clods...
- The heat from the collision would have evaporated/released all elements lighter than X, which includes water. (ed: perhaps water on the moon is more closely related to early earth water coalesced and re-condensed?)
In this scenario, wouldn't much of the released elements have returned thanks to gravity?
Also if we're bringing Theia into it, maybe Theia is the source of the water?
A sample size of one, seems a bit short of that needed to generalize to all other comets... 8-P