The moon probably not formed by one giant impact after all

Improved model assumes multiple smaller collisions with the proto-earth

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The moon probably not formed by one giant impact after all

#1  Postby DavidMcC » Jan 11, 2017 1:16 pm

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2866.html
A multiple-impact origin for the Moon
Abstract
The hypothesis of lunar origin by a single giant impact can explain some aspects of the Earth–Moon system. However, it is difficult to reconcile giant-impact models with the compositional similarity of the Earth and Moon without violating angular momentum constraints. Furthermore, successful giant-impact scenarios require very specific conditions such that they have a low probability of occurring. Here we present numerical simulations suggesting that the Moon could instead be the product of a succession of a variety of smaller collisions. In this scenario, each collision forms a debris disk around the proto-Earth that then accretes to form a moonlet. The moonlets tidally advance outward, and may coalesce to form the Moon. We find that sub-lunar moonlets are a common result of impacts expected onto the proto-Earth in the early Solar System and find that the planetary rotation is limited by impact angular momentum drain. We conclude that, assuming efficient merger of moonlets, a multiple-impact scenario can account for the formation of the Earth–Moon system with its present properties.
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Re: The moon probably not formed by one giant impact after all

#2  Postby crank » Jan 11, 2017 1:33 pm

Interesting. I thought they had this one already figured out fairly well? jeez, science, it can't make up its mind. There is one video, it isn't all that illuminating. It would be nice to have a few simulations with some fairly accessible narration explaining what's what. Of course, not in Nature, that isn't what they do, it's just wishful thinking.
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Re: The moon probably not formed by one giant impact after all

#3  Postby DavidMcC » Jan 11, 2017 1:47 pm

crank wrote:Interesting. I thought they had this one already figured out fairly well? ...

Yeah, so did I! That may have been because the giant impact model proposers hadn't mentioned the problems with it that lead to this new model. I guess the giant impact was easier to calculate, because it would have had fewer fitting parameters, but that, in turn, would tend to lead to a poorer fit.
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Re: The moon probably not formed by one giant impact after all

#4  Postby crank » Jan 11, 2017 2:34 pm

I've been having problems with fitting patterns lately as I keep getting older and older
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Re: The moon probably not formed by one giant impact after all

#5  Postby DavidMcC » Jan 11, 2017 5:17 pm

crank wrote:I've been having problems with fitting patterns lately as I keep getting older and older

What's a fitting pattern?
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Re: The moon probably not formed by one giant impact after all

#6  Postby The_Metatron » Jan 11, 2017 6:10 pm

How coincidental. Two years ago today, I took this composite of Luna:

Luna.jpg
Here's a composite photo of Luna, taken with my Pentax K100D DSLR at prime focus on my 7" Mak-Cas telescope, focal length 2450 mm. I stitched this together with GIMP.
Luna.jpg (46.71 KiB) Viewed 156 times
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Re: The moon probably not formed by one giant impact after all

#7  Postby Macdoc » Jan 11, 2017 8:26 pm

Handheld Leica 100-400 ( 800 mm equiv on the Gx7 )

Image

bet yours is better in full resolution tho
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Re: The moon probably not formed by one giant impact after all

#8  Postby The_Metatron » Jan 11, 2017 10:17 pm

The focus isn't great. The light path distance to the sensor isn't exactly the same as it is to the focusing screen on my camera. No live view of the sensor on that old piece of crap DSLR.

What I really need is a good SBIG camera, and some software to stack a kajillion frames.
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Re: The moon probably not formed by one giant impact after all

#9  Postby newolder » Jan 11, 2017 10:22 pm

The_Metatron wrote:How coincidental. Two years ago today, I took this composite of Luna:

Luna.jpg

It's a good shot of "The woman in the Moon" too:
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Re: The moon probably not formed by one giant impact after all

#10  Postby DavidMcC » Jan 12, 2017 12:57 pm

Newolder, The_Metatron, you are subverting my thread on the formation of the moon. If you want to start your own thread on lunar photography, please feel free to do so.
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