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The current favored theory says that the Moon was formed 4.5 billion years ago when the Earth collided with a mass the size of Mars, dubbed “Theia.” This theory states that the heat generated by the collision would have melted the whole planet before some of the debris spun off to create the Moon. But now, the team at Harvard, led by Associate Professor Sujoy Mukhopadhyay, believe that they’ve found evidence to support that only part of the Earth melted, and that an ancient part still exists within the Earth’s mantle. According to Professor Mukhopadhyay: “The energy released by the impact between the Earth and Theia would have been huge, certainly enough to melt the whole planet. But we believe that the impact energy was not evenly distributed throughout the ancient Earth. This means that a major part of the impacted hemisphere would probably have been completely vaporized, but the opposite hemisphere would have been partly shielded, and would not have undergone complete melting.” The team analyzed the ratios of noble gas isotopes from deep within the Earth’s mantle and compared the results to isotope ratios closer to the surface. They found that 3He to 22Ne ratio from the shallow mantle is significantly higher than the equivalent ratio deep within the mantle. Professor Mukhopadhyay remarked: “This implies that the last giant impact did not completely mix the mantle and there was not a whole mantle magma ocean.”
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. Read more at: phys.org...
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. Read more at: phys.org...
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". Read more at: phys.org...
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.
originally posted by: bottleslingguy
a reply to: bbracken677
first of all you brought up Stitchin (no that's not a typo I'm mocking your mocking him by misspelling his name. a very childish tactic of ad hominem argument) I've been sticking to current scientific based topics and asking you to explain the parts science has no answer for currently. All I get from you is "no one knows" so since you've reached the limits of what you got out of your degree you start focusing on the controversy around him.
And not only that, the "answers" you gave earlier on in our discussion showed clearly you are out of your realm as a geologist discussing this kind of subject. Every time I press you on things like "why is the Moon dead if it accreted the same time as Earth?" or "Why isn't the custard skin on Earth spread out evenly? why did it form all clumped together and then decide to start spreading out?" or "Why COULDN'T the Moon have been captured if its companion collided with a larger, watery giant?" and all I got from you was "No one knows" ( well actually I think you said that last part was possible and ironically for you that is one of Stitchin's contentions so you actually agree with him on that lol) and then when you have nothing intelligent to say, or add or to make a coherent point all you want to do is focus on good ole Stitchin.
It's quite clear YOU DON'T KNOW JACK and are just here trolling
originally posted by: Harvin
One thing that puzzles me is how did the moon become perfectly round? I guess people will say from friction and spinning...just seems odd to me that if it was a collision that the moon is so round.