Mercury - a left-over of the crash that created the Moon?, Highly speculative but maybe worth it |
Mercury - a left-over of the crash that created the Moon?, Highly speculative but maybe worth it |
Dec 7 2007, 12:19 PM
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Member Group: Members Posts: 147 Joined: 14-April 06 From: Berlin Member No.: 744 |
Having agreed upon the Moon being created by a grazing collision with a Mars-sized object, could we give any thoughts to what happened to the impactor afterwards? Since it was a grazing collision, it might have been melted but not destroyed, only with some material ripped from it (and from the Earth) which ended up in Earth orbit to coalsce into what we know as the Moon today. But what happened to the impactor after it passed the Earth? Could it still hang around somewhere in the Solar System? I suppose it would bear some significant markings after the event, for instance have its outer layers stripped. But wait a second... Mercury DOES have its outer layers stripped off, with an unusually high mean density resulting from a core which could be considered oversized for such a small planetary body. In the wake of MESSENGER beginning to reveal Mercury's secrets in January, could anyone bother to give any thoughts to this idea? I am not sure whether it had been put forth previously or not, I am just curious if it could make any sense to have the impactor impact the Earth in a grazing manner and then end up parked in an elliptical orbit close to the Sun, with its outer layers stripped and an "oversized" original core left inside...
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Dec 8 2007, 09:20 PM
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Beginning to wonder here if the detailed history of our Solar System (or any other, for that matter) may be too complex in terms of variables to effectively model. Wouldn't be as difficult if we knew even the total quantity of significant protoplanet impactors to any degree of certainty, but apparently it only takes one to radically alter the end state after two or three or two hundred have already done their jobs.
IMHO, solar system formation is a very chaotic process that may be quite difficult to define even stochastically. We're beginning to see hints of this with the eccentric--in our view--orbital states of some exoplanets. My own guess about Mercury is that it was originally an Earth-sized body in a circular solar orbit that got whacked at least once (and probably many more times) after its formation & differentiation until its rocky outer layers thinned out to where they are today; the large core is an artifact. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Dec 8 2007, 09:58 PM
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
My own guess about Mercury is that it was originally an Earth-sized body in a circular solar orbit that got whacked at least once (and probably many more times) after its formation & differentiation until its rocky outer layers thinned out to where they are today; the large core is an artifact. Keep in mind that Mercury only has 6% of the mass of the Earth. If the other 94% were whacked away, there ought to be an unexplained planet-sized mass somewhere. And the Sun would be an unlikely destination for much if any (Mercury to the Sun is a bigger step in gravitational well-space than Mercury to Pluto). Collisions are much more likely to stick things together than to break things apart. Imagine the impactee as a dartboard and the impactor as a dart. Just about anywhere the dart strikes the dartboard, almost all of the material will end up absorbed by the impactee. It's only for the most glancing blows that a large fraction of the material will escape. And since the impact process isn't TRYING to aim for the edge, the center will receive many more hits than the edge. (Of course, the gravity of the impactee will slightly increase the center-aiming tendency.) So on balance, worlds getting smacked by impactors are going to gain mass over time, not lose it. It would take a single, rare, large impact to take a lot of a world's mass away. In the best case we know of (Earth-Moon), it was only 1.2% of the whole that ended up getting peeled away. We don't have any precedent for a planet-sized body losing much of its mass, and there's good reason to suspect that that would be very rare, and would almost never happen via multiple losses of moderate size, because for every "loss" event, there'd be far more "gain" events. |
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