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A new study finds the gases which formed the Earth’s atmosphere – as well as its oceans – did not come from inside the Earth but from comets and meteorites hitting Earth during the Late Heavy Bombardment period. A research team tested volcanic gases to uncover the new evidence. “We found a clear meteorite signature in volcanic gases,” said Dr. Greg Holland the project’s lead scientist. “From that we now know that the volcanic gases could not have contributed in any significant way to the Earth’s atmosphere. Therefore the atmosphere and oceans must have come from somewhere else, possibly from a late bombardment of gas and water rich materials similar to comets.”
Holland said textbook images of ancient Earth with huge volcanoes spewing gas into the atmosphere will have to be rethought.
According to the theory of the Late Heavy Bombardment, the inner solar system was pounded by a sudden rain of solar system debris only 700 million years after it formed, which likely had monumental effects on the nascent Earth. So far, the evidence for this event comes primarily from the dating of lunar samples, which indicates that most impact melt rocks formed in this very narrow interval of time. But this new research on the origin of Earth’s atmosphere may lend credence to this theory as well.
The researchers analyzed the krypton and xenon found in upper-mantle gases leaking from the Bravo Dome gas field in New Mexico. They found that the two noble gases have isotopic signatures characteristic of early Solar System material similar to me teorites instead of the modern atmosphere and oceans. It therefore appears that noble gases trapped within the young Earth did not contribute to Earth’s later atmosphere.
The study is also the first to establish the precise composition of the Krypton present in the Earth’s mantle.
“Until now, no one has had instruments capable of looking for these subtle signatures in samples from inside the Earth – but now we can do exactly that,” said Holland.
The team’s research, “Meteorite Kr in Earth’s Mantle Suggests a Late Accretionary Source for the Atmosphere” was published in the journal Science.
Sources: Science, EurekAlert
If you have access you can find this article by Holland et al at
http://www.sciencemag.org/cgi/content/abstract/326/5959/1522
LC
If that’s the case, then it probably applies to Mars’ early atmosphere as well, and also to Venus’ atmosphere.
Just imagine the magnitude of the “heavy” bombardbment… Our oceans account for most of the surface of the Earth… And all that came from comets and such!
Fascinating!
It would make sense that ice from comets formed our oceans..surprised anyone would need to do a study to be convinced of this. lol
Boner: The other possibility was that the water was already here when the Earth formed. Indeed, I would be amazed if at least some water on this planet wasn’t here the entire time, but the significance of this study is that it appears that at least most of it came here *after* the planet formed. That’s a significant finding when it comes to the search for life outside our solar system. It raises the question that if other “Earths” out there didn’t have this planetary bombardment occur in their history, would they have enough water/air to support life?
I get this image of God throwing a whopping big snowball at Earth! Or maybe it was a bunch of ’em and using Earth as the moving target! Lol!
I read some postulation that Oort cloud or Kuyper belt objects are displaced by passing stars and give rise to periodic cometary bombardments in which case this must be fairly common in other solar systems
In one sense the whole Earth and the other planets were formed from material coalescing in the early solar system. This included not just the solid material of the planet but the atmosphere as well. So as Sagan put it we are all made of star dust.
LC
I’m confused. If the evidence that the atmosphere didn’t come from volcanic gasses is that the volcanic gasses resemble gasses from meteorites (with respect to isotopic signatures), then the last thing you’d conclude is that the atmosphere came from meteorites instead.
Maybe the key lies in the difference between meteorites and comets, but the introductory paragraph clearly says “meteorites AND comets”, so that’s not very helpful.
This has all sorts of interesting implications.
Unless the Earth atmosphere derived from earlier impacts such as Theia (in which, as I understand it, astronomers have models suggesting that Earth captured most of both “planetoid” atmospheres and left the Moon airless), there likely wasn’t a primitive atmosphere for abiogenesis to occur in before the LHB.
If that is the case, abiogenesis was really fast on its feet as soon as the conditions were favorable. That argues that life is exceedingly easy.
But if that happened it also introduces difficulties for habitability in other systems, as the LHB was caused by giant planet migration which won’t happen everywhere.
Luckily, if the Theia models are correct, the last coalescent impacts could have brought enough water and atmosphere. That would be the most natural assumption, again seeing that LHB was contingent while coalescence wasn’t. And at a minimum the jury is still out, AFAIU.
@ Boner, Dave Finton:
I’ve got the impression lately from glanced press releases that there may be a lot of water content in asteroids, and also specific “comet like” bodies in the asteroid belt. I hesitate to say “population” for the later as for all I know there may be a continuous distribution.
@ Adrian Morgan:
I think they see a difference between “a meteorite or fractionated solar nebula source” for “samples derived from Earth’s mantle”, and a source which had its volatiles processed by “later volatile capture rather than impact degassing or outgassing of the solid Earth during its main accretionary stage.”
That is, there seems to be a difference in isotope ratios between capturing, say, (most of) Theia’s gases directly at its impact or having (most of) them degas through (and from) minerals later by the heat of impact.
What that means exactly I don’t know, as luck would have it I don’t have access to the paper today.
@ Torbjorn Larsson OM – “If that is the case, abiogenesis was really fast on its feet as soon as the conditions were favorable. That argues that life is exceedingly easy.”
How does the notion that “life is exceedingly easy” survive in an era of mature science? I agree life seemed to arise quickly – it just fell here! Like Nobel-prize winner Svante Arrhenius and others have proposed. I’ve been researching this notion for some time, and there’s a real blatant attempt on the part of some to continually squealch and ridicule the panspermia or transpermia theories. Please don’t support this degradation of science by neglecting the possibility of transpermia.
One has to put quotes around “transpermia” and “panspermia”. It is abundantly clear that there is a rich base in organic chemicals and compounds available in the detritus of space, but classifying that as the transfer of life or the pan-existence of life is where such theories cause ridicule. The conditions of space are unlikely to support complex life across the vast distances, while clearly supporting not only the existence, but the creation of organic compounds that, when presented with friendly conditions, can, over millions or billions of years, almost certainly reach what we would call life. Proposing such as an intelligent process is likely to invite even more ridicule.
Small amounts of water can be found in meteoroids which land on Earth today. If you think back 4 billion years, and the amount of meteors floating around the sun at that time (Surely which contained a lot more water/ice than present ones do), it isn’t difficult to imagine water coming from them. Even in amounts to form the oceans. Based on evidene showing the Earth had a lot of water on it less than 2 million years after being formed, a lot came at a very fast rate.
For me the question isn’t about where oxygen and hydrogen came from. It is where our nitrogen comes from. Especially since there is only one other body in our solar system which has any.