Suggests comet bombardment contributed to forming oceans
From the European Space Agency: Did Earth’s oceans come from comets?
ESA’s Herschel infrared space observatory has found water in a comet with almost exactly the same composition as Earth’s oceans. The discovery revives the idea that our planet’s seas could once have been giant icebergs floating through space.
The origin of Earth’s water is hotly debated. Our planet formed at such high temperatures that any original water must have evaporated. Yet today, two-thirds of the surface is covered in water and this must have been delivered from space after Earth cooled down.
Comets seem a natural explanation: they are giant icebergs travelling through space with orbits that take them across the paths of the planets, making collisions possible. The impact of comet Shoemaker-Levy 9 on Jupiter in 1994 was one such event. But in the early Solar System, when there were larger numbers of comets around, collisions would have been much more common.
However, until now, astronomers’ observations have failed to back up the idea that comets provided Earth’s water. The key measurement they make is the level of deuterium – a heavier form of hydrogen – found in water.
All the deuterium and hydrogen in the Universe was made just after the Big Bang, about 13.7 billion years ago, fixing the overall ratio between the two kinds of atoms. However, the ratio seen in water can vary from location to location. The chemical reactions involved in making ice in space lead to a higher or lower chance of a deuterium atom replacing one of the two hydrogen atoms in a water molecule, depending on the particular environmental conditions.
Thus, by comparing the deuterium to hydrogen ratio found in the water in Earth’s oceans with that in extraterrestrial objects, astronomers can aim to identify the origin of our water.
All comets previously studied have shown deuterium levels around twice that of Earth’s oceans. If comets of this kind had collided with Earth, they could not have contributed more than a few percent of Earth’s water. In fact, astronomers had begun to think that meteorites had to be responsible, even though their water content is much lower.
Now, however, Herschel has studied comet Hartley 2 using HIFI, the most sensitive instrument so far for detecting water in space, and has shown that at least this one comet does have ocean-like water.
“Comet Hartley’s deuterium-to-hydrogen ratio is almost exactly the same as the water in Earth’s oceans,” says Paul Hartogh, Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, who led the international team of astronomers in this work.
The key to why comet Hartley 2 is different may be because of where it was born: far beyond Pluto, in a frigid region of the Solar System known as the Kuiper Belt.
The other comets previously studied by astronomers are all thought to have formed near to Jupiter and Saturn before being thrown out by the gravity of those giant planets, only to return much later from great distances.
Thus the new observations suggest that perhaps Earth’s oceans came from comets after all – but only a specific family of them, born in the outer Solar System. Out there in the deep cold, the deuterium to hydrogen ratio imprinted into water ice might have been quite different from that which arose in the warmer inner Solar System.
Herschel is now looking at other comets to see whether this picture can be backed up.
“Thanks to this detection made possible by Herschel, an old, very interesting discussion will be revived and invigorated,” says Göran Pilbratt, ESA Herschel Project Scientist.
“It will be exciting to see where this discovery will take us.”
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
So God put the water here by chucking a lump of ice at it after it had cooled? ;-).
Interesting !!!
Mr Watts have you seen this? [ I would have left it on your “Tips and notes” pages but dialup just won’t load it anymore 🙂 ]
Huge ‘Ocean’ Discovered Inside Earth
http://www.livescience.com/1312-huge-ocean-discovered-earth.html
I seem to remember that recently comets made from just ice were discovered by seeing specks in photographs of aurora. These were about the size of houses, and being all ice, simply melt and become part of the earth’s atmosphere. It was estimated from the rate of occurrence that all the water of the earth could have come from this source over a period of about 1 billion years. Or is my memory failing me.
Observations. What do they expect to learn that way?
20 October which year?
The cosmos is a source for infinite speculation.
Here we go again, every time Scientists make an observation then speculate about origins it sparks a huge debate between religion and science and poo starts to get flung in every which way. All I know is I really don’t care where they think water might come from. Focus on the observation and leave the rest to us to conclude…please! I don’t care anymore about scientists thoughts on origins. In the end water doesn’t taste better because it came from a comet or created by someone, though I suppose it could alter your appreciation of it a bit. For all those who want to hotly debate this, I recommend you go enjoy a cold glass of water instead, it will be more beneficial in the end and you will save yourself some frustration…cheers!
Anthony,
I love when a good comet helps to prove my research!
Water was here long before this theory of being bombarded by comets of water.
What do you think kept toxic gases compressed when this planet was cooling?
Massive amounts of water that has been lost to space at a rate of 1.25mm/10,000 years.
Why do you think we have all this salt left over around the planet under a billion years old?
I like the sound of that. The theory has been hanging around for years & seemed plausible. However, a question, if the water on Earth evaporated due to the heat generated in its formation, why would it have “disappeared” as opposed to merely being stored in the atmosphere ready to reform as water as soon as the Earth cooled?
Isn’t water outgassed from volcanoes? I would think the most likely explanation is that water ice was buried in the formation of Earth and released late enough to remain and eventually form oceans as the Earth got cooler. Venus didn’t get it’s CO2 from comets.
The article states: “The origin of Earth’s water is hotly debated. Our planet formed at such high temperatures that any original water must have evaporated.”
But actually those who favor the idea that most of the Earth’s seawater came from internal sources (volcanic steam and outgassing from the Earth’s crust) say something else. They say that the primordial Earth’s atmosphere was much denser then, so that the boiling point of water at sea level was much higher. Hence, liquid water may have existed even at temperatures exceeding 212° F / 100° C.
(P.S., Ian Plimer notes this in his “Heaven and Earth” — a must-have title for the AGW-skeptic’s bookshelf)
It’s only a hop, skip and jump from this to “Comets cause catastrophic sea level rise, we must rid the solar system of comets”
A nasty, sneaking, heretical thought: is it absolutely known that Earth was once completely molten (aside from the major moon-forming impact, that is)? Consider a pile of space rubble accreting under gravity. The centre gets heated and melts, gradually expanding the melt front, but will it actually reach the surface? I don’t have much problem envisaging a rubbly, dusty surface over a molten inner, with volcanoes erupting and gradually forming a crust, but with the water still liquid on top.
As I said, just a thought.
(snip) Our planet formed at such high temperatures that any original water must have evaporated. (/snip)
“Evaporated”, or “evaporated and left the earth permanently”?
It makes sense that any water would have evaporated, but it does not make sense that it would not condense again at some later time.
It’s Yamal all over again… 1 comet makes the case.
I don’t get this at all. It sounds too much like “Was God a Spaceman?” I mean water doesn’t breed and I seriously doubt that any comet that DIDN’T destroy the earth would deposit enough ice to fill the oceans.
Isn’t it more likely that it comes from hydrogen from volcanoes burning in the atmosphere, or something ?
A single comet vs. multiples that didn’t check out .. I think the most basic math obviously dismisses the hypothesis unless low deuterium count comets have significantly higher probability of hitting earth than their high deuterium count brethren.
Anthony, you are doing a fantastic job in making these things available so quickly.
Comets seem a pretty logical source of water on Earth to me. The old portents of doom have also always seemed a highly likely candidate for massive climate change to me – all that water boiling off in the upper atmosphere. How big a comet would you need to actually impact – even then, what would be left – a nice lake? Would we even notice a few chunks of ice arriving pretty much continuously? .
Why would anyone expect the ratio of deuterium in the oceans to be the same as deuterium in comets? I’m no expert, but the rates of reaction of deuterated organic compounds are dramatically different to hydrogen-based organic compounds, since all known life is hydro(gen)-carbon based, surely the presence of life would dramatically alter the H to D ratio in seawater? You get a lot of kinetics in 4 billion years…
What about the various icy moons? Similar or not? Worth a look…
I’ll probably be the 37th post to mention “Panspermia”.
Of course the God was an Astronaut thing does rather fit, someone called Slartibartfast probably had a hand in it, he won an award for the fjiords you know! 😉
John Barrett says:
October 6, 2011 at 7:21 am
“I don’t get this at all. It sounds too much like “Was God a Spaceman?” I mean water doesn’t breed and I seriously doubt that any comet that DIDN’T destroy the earth would deposit enough ice to fill the oceans.”
Think many (“house-sized”) small water comets coming in all the time.
http://csep10.phys.utk.edu/astr161/lect/comets/smallcomets.html
My issue with the “water came from comets” is that it ignores a likely common cause. I say water on earth came from the same source as the comets and the comets are just some minuscule left overs. I’ve say water is created in some sort of solar or other cosmic process, and recent discovery of a star emitting jets of water shows this to be at least one origin of galactic H20 supplies.
Water is abundant in this universe, which will sadly make so many science fiction plots ridiculous.
Scientists discover water cloud in galaxy…
http://www.filtersfast.com/blog/index.php/2011/08/scientists-discover-water-cloud-in-a-galaxy-far-far-away/
Star Found Shooting Water “Bullets”
http://news.nationalgeographic.com/news/2011/06/110613-space-science-star-water-bullets-kristensen/
Black Hole Holds Universe’s Biggest Water Supply
http://www.wired.com/wiredscience/2011/07/black-hole-holds-universes-biggest-water-supply/
“Our planet formed at such high temperatures that any original water must have evaporated. Yet today, two-thirds of the surface is covered in water and this must have been delivered from space after Earth cooled down.”
Must have been delivered from space? There are other options. Maybe the water changed state from gas to liquid. Or maybe it was made from a chemical reaction that combined hydrogen and oxygen.
What difference does it make?
Wheter a big pile of rock was forming first in space, and then bombarded by other lumps of ice, or, one big lump of rock and ice was formed in one go……