GRAIL and the Mystery of the Missing Moon

[Dover]

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The "Big Splat." Four snapshots from a computer simulation
of a collision between the Moon and a smaller companion show
how the splattered companion moon forms a mountainous region on
one side of the Moon. Credit: M. Jutzi and E. Asphaug, Nature.



Sept. 7, 2011: As early as Sept. 8th, NASA's GRAIL mission will blast off to uncover some of the mysteries beneath the surface of the Moon. That cratered gray exterior hides some tantalizing things – even, perhaps, a long-lost companion.

If a paper published recently in the journal Nature* is right, two moons once graced our night skies. The proposition has not been proven, but has drawn widespread attention.

"It's an intriguing idea," says David Smith, GRAIL's deputy principal investigator at MIT. "And it would be a way to explain one of the great perplexities of the Earth-Moon system – the Moon's strangely asymmetrical nature. Its near and far sides are substantially different."

The Moon's near side, facing us, is dominated by vast smooth 'seas' of ancient hardened lava. In contrast, the far side is marked by mountainous highlands. Researchers have long struggled to account for the differences, and the "two moon" theory introduced by Martin Jutzi and Erik Asphaug of the University of California at Santa Cruz is the latest attempt.

Scientists agree that when a Mars-sized object crashed into our planet about 4 billion years ago, the resulting debris cloud coalesced to form the Moon. Jutzi and Asphaug posit that the debris cloud actually formed two moons. A second, smaller chunk of debris landed in just the right orbit to lead or follow the bigger Moon around Earth...cont'd

http://science.nasa.gov/science-news/science-at-nasa/2011/07sep_twomoons/

[Warpy]

1. Given that the dominant theory about the Moon's creation

is from another "big splat" of the Earth with a smaller planet, this makes sense, that the ejecta from that splat could have reformed into two separate bodies with orbits that crossed each other. There is also evidence of a big splat on the Martian surface and it seems reasonably certain that big splats occurred more often than not during the period of peak bombardment in the earliest solar system.

Plus, I just love saying "big splat."

[Ready4Change]

2. Early Solar system as lava lamp.

Not making fun of this. It's just that a lot of the computer modeling of events like this that I see remind me of lava lamps.

[Dover]

3. Been there done that...

http://www.youtube.com/watch?v=DLOth-BuCNY&feature=related