From the European Association of Geochemistry
New isotopic evidence supporting moon formation via Earth collision with planet-sized body
A new series of measurements of oxygen isotopes provides increasing evidence that the Moon formed from the collision of the Earth with another large, planet-sized astronomical body, around 4.5 billion years ago. This work will be published in Science* on 6th June, and will be presented to the Goldschmidt geochemistry conference in California on 11th June.
Most planetary scientists believe that the Moon formed from an impact between the Earth and a planet-sized body, which has been given the name Theia. Efforts to confirm that the impact had taken place had centred on measuring the ratios between the isotopes of oxygen, titanium, silicon and others. These ratios are known to vary throughout the solar system, but their close similarity between Earth and Moon conflicted with theoretical models of the collision that indicated that the Moon would form mostly from Theia, and thus would be expected to be compositionally different from the Earth.
Now a group of German researchers, led by Dr. Daniel Herwartz, have used more refined techniques to compare the ratios of 17O/16O in lunar samples, with those from Earth. The team initially used lunar samples which had arrived on Earth via meteorites, but as these samples had exchanged their isotopes with water from Earth, fresher samples were sought. These were provided by NASA from the Apollo 11, 12 and 16 missions; they were found to contain significantly higher levels of 17O/16O than their Earthly counterparts.
Dr Herwartz said “The differences are small and difficult to detect, but they are there. This means two things; firstly we can now be reasonably sure that the Giant collision took place. Secondly, it gives us an idea of the geochemistry of Theia. Theia seems to have been similar to what we call E-type chondrites**.If this is true, we can now predict the geochemical and isotopic composition of the Moon, because the present Moon is a mixture of Theia and the early Earth. The next goal is to find out how much material of Theia is in the Moon”.
Most models estimate that the Moon it is composed of around 70% to 90% material from Theia, with the remaining 10% to 30% coming from the early Earth. However, some models argue for as little as 8% Theia in the Moon. Dr Herwartz said that the new data indicate that a 50:50 mixture seems possible, but this needs to be confirmed.
The team used an advanced sample preparation technique before measuring the samples via stable isotope ratio mass spectrometry, which showed a 12 parts per million (± 3 ppm) difference in 17O/16O ratio between Earth and Moon.
Dr Daniel Herwartz will present “The elevated Δ17O composition of the Moon relative to the Earth” to the Goldschmidt conference, Sacramento, California, on 11th June at 09.45, Eastern Time. The Goldschmidt conference is the world’s leading annual conference on geochemistry, http://goldschmidt.info/2014/
Please mention this Goldschmidt presentation in any story which results from this press release.
Conference Abstract
The elevated Δ17O composition of the Moon relative to the Earth
D. HERWARTZ, A. PACK, B. FRIEDRICHS AND A. BISCHOFF
We present the first isotopic evidence for giant impactor material in lunar rocks. The Moon presumably formed from the debris of a giant collision between two proto-planets (‘giant impact hypothesis’). Most numerical models of the collision predict that the Moon dominantly formed from impactor material. Thus, the Moon should inherit the isotopic composition of the impactor. So far, however, no isotopic difference between the Earth and the Moon has been resolved. We have measured the triple oxygen isotopic composition of APOLLO basalts using an improved protocol [1]. We show that the Δ17O isotopic compositions of lunar APOLLO basalts is elevated by 12 ± 3 ppm relative to the Earth. We also show that enstatite chondrites (EC) comprise an even higher Δ17O of 51 ± 6 ppm relative to the Earth. Thus, EC cannot be the sole building blocks of the Earth. Instead EC may resemble the composition of the giant impactor. If so, the Moon may be composed of ~40% impactor material, consistent with recent numerical models of the collision [2,3]. In an alternative scenario the lower Δ17O composition of the Earth could reflect a late veneer with low Δ17O. Addition of 0.5% carbonaceous chondrites would be sufficient to lower the Δ17O of silicate Earth by 12 ppm.
Additional Notes
*The paper on which this presentation is based will be published in Science on 6th June 2014 (details below). The full paper will be available after the embargo at: http://www.sciencemag.org/lookup/doi/10.1126/science.1251117
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Now that is interesting!
“The next goal is to find out how much material of Theia is in the Moon”.
Big question. Why? Who cares? Sounds like a makework task from the Great Depression’s New Deal program.
“Big question. Why?”
Because the knowledge is worth having, for itself. Not everything has to have a practical application.
arthur4563 says:
June 5, 2014 at 12:06 pm
IMO most of Theia is on earth, or in it, if the hypothesis be valid.
The impact hypothesis has been the best supported explanation for moon formation for about 40 years.
The latest wrinkle is that slow-motion collision with a second moon formed the highlands on the dark side.
“Most models estimate that the Moon it is composed of around 70% to 90% material from Theia, with the remaining 10% to 30% coming from the early Earth. However, some models argue for as little as 8% Theia in the Moon. Dr Herwartz said that the new data indicate that a 50:50 mixture seems possible, but this needs to be confirmed.”
Why do I have an ugly feeling that this “research” is done on some computer modeling concept where you write the program with your belief set in place and lo and behold, the program output is “proof” that it happened?
“Dr Herwartz said “The differences are small and difficult to detect, but they are there. This means two things; firstly we can now be reasonably sure that the Giant collision took place. Secondly, it gives us an idea of the geochemistry of Theia.” Ah, but the are “significant” differences, even though they are small and hard to detect. And we are probably talking proxies, by the way, again being treated as if they are absolutes.
Looks like more than just climate science has lost its way.
… and Mars was in collision with a large body, sometime long ago, losing mass and atmosphere. Could Mars have been Theia?
This doesn’t seem like news to me… it’s long been accepted that the Moon was formed by a mega-collision. Is there something new here?
The moon is Green Cheese, dammit.
The science is settled.
Is this a follow up on something I read about several decades ago or is the study completly recycled …?
This is not a new theory. In fact it is the most widely accepted one for lunar formation, based on lunar rock analysis ( little heavy mantel basalt, lots of light crustal silicate) and orbital spin (we never see the back side of the moon from Earth. There must be a reason.)
What is new is the additional confirming isotope analysis.
The hype here is equivalent to the 2014 paper rediscovering what Darwin knew in 1834, that coral atolls grow and decline with sea level, as corals are alive!
It seems most scientific papers now come with attached obligatory hype. Still, interesting for those who did not know how the moon was made. Watt else is up with astrophysics? Gravity wave polarization of the CMBT, simultaneously validating Einstein’s general relativity AND the Big Bang/ Inflation. Nobels forthcoming after second validation by a European satellite end of this year.
Note the science thingy. A second validation of an observation which itself only confirms theories already tested otherwise (black holes for general relativity,the mere existence of the CMBT for Bang/inflation). Now in climate science, we have missing heat where the laws of thermodynamics say it cannot go, and a darned pause that should not be, and polar bears thriving instead of dying. Some sort of a climate science thingy/ reality disconnect. Must be a Matrix sort of reality, because the climate computer models cannot be wrong… Right, Morpheus? All topical essays in my somewhen (soon?) next book.
sophocles says:
June 5, 2014 at 12:19 pm
No. All large bodies in the solar system have sustained collisions.
Mars took a hit about 4 BA, but its impact wasn’t the same one which formed earth’s moon, hypothetically. This conclusion is based upon modeling, but of a higher order than GIGO, worse than worthless, repeatedly falsified GCMs based on unwarranted assumptions:
http://www.universetoday.com/15262/two-faces-of-mars-explained/
Now that really was an Extinction level event!
Might that planet sized body have been named Alice?
Oh wait. This was about how it was formed.
Never mind.
Hasn’t that been the theory all along?
I really want to know when Tyson DeGrasse is going to edited that Cosmos episode.
There have been several storis on this in the last few years. This story claims they have
data from isotope analysis to back up the hypothesis.
http://www.pnas.org/content/108/43/17604.full
http://phys.org/news/2012-10-massive-planetary-collision-zapped-key.html
[snip – irrational rant, wildly off topic -mod]
So maybe Veliskovsky was not so much a nut case after all, who would have thunk it!(Galileo was one as well).
Was the pacific ocean it’s impact zone? And did it form the pacific ring of fire?
If it happened then, it can happen again. We should apply the precautionary principle and start dealing with it now. Otherwise we’re doomed.
jmorpuss says:
June 5, 2014 at 3:13 pm
Not exactly, but so much crust missing up there in orbit helps account for plate tectonics.
Here’s a NASA animation of the two-moon hypothesis to which I alluded above:
Did this event give Earth it’s water, as the moon gave up all it’s ice as water vapor on impact?
jmorpuss says:
June 5, 2014 at 4:21 pm
Earth’s water mostly comes from comets, although chemical processes here also produced some, largely lost during impact events.
A possible Woolly kill:
http://old.post-gazette.com/healthscience/20000228woolly2.asp
Oops. Sorry. Wrong post.
For the two moon theory to stand up your saying Earth has always had its strong electromagnetic properties that would hold these moons in place. I’m not shaw this is correct ,it’s my belief that impact created Earths strong. Electromagnetic field lines so Earth was capable of holding a saterlite of the size of the moon . If you strike a iron bar hard enough you will create magnatism . Until Earth was impacted it was as lifeless as Venus and Mars because Earth also had weak magnetic properties incapable of holding on to a atmosphere let alone a moon. Just my thoughts