[Hamucevasiop]

New research eclipses existing theories on moon formation
by Staff Writers
Oxford UK (SPX) Aug 30, 2012

File image.


The Moon is believed to have formed from a collision, 4.5 billion years ago, between Earth and an impactor the size of Mars, known as "Theia." Over the past decades scientists have simulated this process and reproduced many of the properties of the Earth-Moon system; however, these simulations have also given rise to a problem known as the Lunar Paradox: the Moon appears to be made up of material that would not be expected if the current collision theory is correct.

A recent study published in Icarus proposes a new perspective on the theory in answer to the paradox.

If current theories are to be believed, analyses of the various simulations of the Earth-Theia collision predict that the Moon is mostly made up of material from Theia.

However, studying materials from both Earth and the Moon, shows remarkable similarities. In fact, elements found on the Moon show identical isotopic properties to those found on Earth.

Given it is very unlikely that both Theia and Earth had identical isotopic compositions (as all other known solar system bodies, except the Moon, appear to be different) this paradox casts doubt over the dominant theory for the Moon formation.

Moreover, for some elements, like Silicon, the isotopic composition is the result of internal processes, related to the size of the parent body. Given Theia was smaller than Earth, its Silicon isotope composition should have definitely been different from that of Earth's mantle.

A group of researchers from the University of Bern, Switzerland, have now made a significant breakthrough in the story of the formation of the Moon, suggesting an answer to this Lunar Paradox.

They explored a different geometry of collisions than previously simulated, also considering new impacts configurations such as the so-called, "hit-and-run collisions," where a significant amount of material is lost into space on orbits unbound to the Earth.

"Our model considers new impact parameters, which were never tested before. Besides the implications for the Earth-Moon system itself, the considerably higher impact velocity opens up new possibilities for the origin of the impactor and therefore also for models of terrestrial planet formation," explains lead author of the study, Andreas Reufer.

"While none of the simulations presented in their research provides a perfect match for the constraints from the actual Earth-Moon-system, several do come close," adds Alessandro Morbidelli, one of the Icarus' Editors.

"This work, therefore, suggests that a future exhaustive exploration of the vast collisional parameter space may finally lead to the long-searched solution of the lunar paradox."






http://www.space-travel.com/reports/...ation_999.html

[toponlinecasinoer]

If current theories are to be believed, analyses of the various simulations of the Earth-Theia collision predict that the Moon is mostly made up of material from Theia. That was not my understanding. I would not be surprised if this report has misstated/overstated the situation.

[viagradiscounttt]

That was not my understanding. I would not be surprised if this report has misstated/overstated the situation.

Not much different from the earth's makeup I thought.

I'll see if I can find anymore on this Martin.

[LypeReexy]

Well, on the one hand this report is essentially the press release from the journal, so they are the ones with the responsibility if it is misspoken.

On the other hand, the fact that I can't easily find a reference to the "lunar paradox" that is not a version of this story deepens my suspicion.

[Woziwfaq]

The Moon was ejected from Earth... [just as all moons are... and all planets are ejected... and most probably stars]

The process is similar to radioactivity

[DoctorGordanBens]

The Moon was ejected from Earth... [just as all moons are... and all planets are ejected... and most probably stars]

The process is similar to radioactivity

how come when you post this concept nobody complains?

[kazinopartnerkae]

how come when you post this concept nobody complains? cos we've heard it all before, many times and so tend to ignore him. you should too. but that is up to you.

[WrigleyMike]

how come when you post this concept nobody complains?

Because posting complaints about Zarkov's delusions has about the same effect as monkeys throwing their own faeces.

[eFDMBwKH]

Because posting complaints about Zarkov's delusions has about the same effect as monkeys throwing their own faeces.

until a poster contravenes the guidelines there is no reason to ban them.

everyone has the right to post. and everyone has the right to use the ignore function.

[lodsemelf]

i don't think banning was geoffs point. just that it was pointless arguing with zarkov.

[BILBONDER]

i don't think banning was geoffs point. just that it was pointless arguing with zarkov.

Ed Zachary!

[ibupronec]

it was the monkey faeces that gave it away.

[BenWired306]

The Moon was ejected from Earth... [just as all moons are... and all planets are ejected... and most probably stars]

The process is similar to radioactivity

That hypothesis is wrong and there is absolutely no evidence to ever suggest it happened that way.
I put it down to your anti-establishement thingy....

[Faungarne]

Well I'll put my hand up and say I was wrong - seems that hydrodynamic simulations do indeed derive 40-75% of lunar material from the impactor.

Here's another paper that discusses this and here's a webpage:
Junjun Zhang and her colleagues investigated whether titanium could also have exchanged between the proto-lunar disk and Earth, resulting in the same Ti isotopic composition in each body. An important difference, however, between titanium and oxygen is that titanium is more refractory, so it would have lingered in the orbiting magma rather than been exchanged through the atmosphere. Their calculation suggests that the refractory element isotopes would have equilibrated in about 30 years, possibly enough time if the disk lasted long enough. The likely way significant exchange would have happened is if the orbiting magma was highly turbulent and substantially mixed. Zhang and colleagues point out that this concept needs more quantitative study.

An alternative explanation is that the planetary-accretion calculations overestimate the apparent variations in mixing of the building-block materials. Perhaps large objects in the inner solar system did not vary much in composition after accretion because numerous planetesimals were averaged together, muting chemical differences that existed throughout the inner solar system.

Another alternative is that the simulations of the giant impact completely misjudge the amount of the impactor that ends up in the Moon. Maybe the Earth provides almost all the material. The models seem to be quite robust, however, and it is unlikely that only tiny amounts of the impactor end up in the Moon, considering that much of the molten and vaporized rock that is blasted into orbit comes from the interface between Theia and the proto-Earth. Zhang and her colleagues raise the possibility that Theia was an icy intruder from the outer solar system that did not add much rock (hence very little titanium), but delivered lots of water-rich vapor that might have facilitated the exchange of oxygen isotopes. Interesting possibilities abound.

Importantly, the data reported by Zhang and coauthors do not disprove the giant impact hypothesis. Those old crucial pieces of the puzzle—angular momentum of the Earth-Moon system and the small lunar metallic core—are still there. Instead, these high-quality measurements of the similarity of titanium isotopes in Earth and Moon give cosmochemists an additional tool for probing the complicated process of lunar formation by a giant impact.

[BypeVupyide]

don't ya love simulations... better than reality...ooooh!!!

[FalHaitle]

What a stupid comment.

Obviously if there was a way of directly observing events that happened a long time ago like the formation of the Moon then that would be better evidence. Since there isn't we need to interpret the evidence that we do have and simulations based on accepted physical principles are one tool for doing so.

[snova]

What a stupid comment.

You expected an intelligent comment from that quarter?

[Golotop]

No, although it's a chance to point out a kind of stupidity that is sadly not confined to the Zarkovians.

[SinyugiN]

No, although it's a chance to point out a kind of stupidity that is sadly not confined to the Zarkovians.

Has Evil Martin hacked Good Martin's account again?

[Sxscdergh]

The Moon was ejected from Earth... [just as all moons are... and all planets are ejected... and most probably stars]

Just for the sake of speculation, I would like to examine this idea. I wouldn't go as far as providing a scenario for Zarkov's star ejection, but providing a scenario in which planetary formation might occur through an ejected body mechanism at least provides a genuine discussion.

The simple scenario would involve the early orbits of the gas giants. If it is standard for gas giants to form in a close orbit to their star, why would it not be conceivable that the progression of their orbits to a greater distance might involve the shedding of the heavier elements they may have accumulated?