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Space Science

Saturn's Rings Formed From Large Moon Destruction 115

Posted by CmdrTaco
from the now-it's-definitely-no-moon dept.
Matt_dk writes "The formation of Saturn's rings has been one of the classical if not eternal questions in astronomy. But one researcher has provided a provocative new theory to answer that question. Robin Canup from the Southwest Research Institute has uncovered evidence that the rings came from a large, Titan-sized moon that was destroyed as it spiraled into a young Saturn."
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Saturn's Rings Formed From Large Moon Destruction

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  • Re:Obvious? (Score:2, Informative)

    by Anonymous Coward on Thursday October 07, 2010 @11:00AM (#33824754)

    Jupiter already has rings.

    http://en.wikipedia.org/wiki/Rings_of_Jupiter [wikipedia.org]

  • Re:Obvious? (Score:5, Informative)

    by Chemicles (771024) on Thursday October 07, 2010 @11:08AM (#33824854)
    I think the article's content is more along the lines of "this new theory explains how Saturn's rings were formed, with their particular composition, while also explaining the other nearly-pure ice moons in the vicinity". The theory in the article is a little more comprehensive than "Saturn's rings were caused by a collision" (even though the summary was lacking information and seemed to imply that... go figure).
  • Re:that's no moon! (Score:5, Informative)

    by mcgrew (92797) * on Thursday October 07, 2010 @11:09AM (#33824872) Homepage Journal

    The rings/moon's firewalled off here, but I found a BBC article [bbc.co.uk] that's not.

    I've wondered for a long time if the asteroid belt was formed by some sort of collision, and thought about writing a science fiction story about an interstellar war between Mars and the no longer existing fifth planet (story would end with Mars losing its atmosphere and Planet Five being blown to bits).

    Astronomers? Is this possible, or likely? I know that's where current theory says our moon came from; a Mars sized object that collided with a young Earth.

  • by Colonel Korn (1258968) on Thursday October 07, 2010 @11:22AM (#33825030)

    You need to read more astronomy textbooks.

    The same side is facing earth because earth's gravity has absorbed/slowed/negated its angular momentum.

    The moon is moving closer to earth, very slowly.

    Although it generally accepted that the moon is a product of a collision of a body with earth.

    Replying to undo my informative moderation because though correct about the tidal locking, you got the Moon's slow change in orbital distance backwards. It's slowly moving farther away from Earth.

  • by mcgrew (92797) * on Thursday October 07, 2010 @11:33AM (#33825206) Homepage Journal

    Not exactly. It was a Mars sized object, and the collision completely demolished it. For a while, the earth had a ring formed from the collision. The ring eventually coalesced to form the moon.

    The collision caused the earth's rotation. Ar one time a day on earth lasted three hours. The farther the moon gets from the earth, the more the earth's rotation slows.

    I wonder what the sky would have looked like then? The moon would have been HUGE, tides would have been tremendous.

  • by Burnhard (1031106) on Thursday October 07, 2010 @11:35AM (#33825246)
    It's about an inch a year I think. So in 1,000,000,000 years time it'll be 4,000km further away than it is now (assuming, incorrectly probably, that it's always 1" per year, i.e. that the effect doesn't get smaller as it moves away). I'm not sure how far away it has to be to be in danger of escaping orbit entirely though. I expect it's a lot, lot further than that!
  • by MozeeToby (1163751) on Thursday October 07, 2010 @11:37AM (#33825284)

    We always see the same side of the moon because of tidal locking [wikipedia.org]. It doesn't have anything to do with how the moon formed except in that the impact hypothesis puts the new moon close enough to the Earth that it became tidally locked fairly quickly, but that isn't unique to the impact hypothesis. In very basic terms it works like this:

    1) Tides cause bulges on one or both bodies
    2) The material that the bodies are made of resists that bulge so the bulge is never precisely where it it 'should' be gravitationally speaking. If the body rotates slower than it revolves the bulge will be behind, faster than it revolves and the bulge will be ahead. Let's say the bulge is ahead in this example.
    3) The orbiting body (relative to the tidal bulge) is slightly more attracted to the bulge, since it is slightly closer than the rest of the planet. Since the bulge is ahead this pulls the bulge back (causing the bulging body to slow its rotational speed) and pulls the orbiting body as a whole forward (causing it to increase it's revolution speed).

    In the Earth/Moon system, this has locked the moon's rotation rate to it's revolution rate. The same isn't (yet) true for the earth, if you stand on the moon you will see all sides of the Earth. However, that is very, very slowly changing. Each trip around the planet, the moon steals some of the Earth's rotational energy and turns it into orbital energy, raising the orbit of the moon a tiny bit and lengthening the day a tiny bit.

  • Re:that's no moon! (Score:2, Informative)

    by Duodecimal (938540) on Thursday October 07, 2010 @11:58AM (#33825574)
    It'd be a tiny itty bitty planet. All the asteroids together are only 4% of the Moon's mass. http://en.wikipedia.org/wiki/Asteroid_Belt#Formation [wikipedia.org]
  • by CheshireCatCO (185193) on Thursday October 07, 2010 @12:04PM (#33825670) Homepage

    The collision caused the earth's rotation. Ar one time a day on earth lasted three hours. The farther the moon gets from the earth, the more the earth's rotation slows.

    I think you're confusing two things, here. The collision did almost surely affect the Earth-Moon system's total angular momentum, but the early spin rate and the gradual slowing of the Earth isn't due to the collision (except indirectly), but due to tides transferring angular momentum from Earth to the Moon.

    We really don't know Earth's initial spin state since there's no way to find that in any sort of record. (At least none I can think of. It just doesn't leave much of a mark.)

  • Re:that's no moon! (Score:3, Informative)

    by Duodecimal (938540) on Thursday October 07, 2010 @12:05PM (#33825688)
    I should have read the article further. It's hypothesized that the belt contained as much as an earth-mass of material. But overall, it never coalesced into a planet due to being disturbed by Jupiter's gravity.
  • Re:New? (Score:3, Informative)

    by SnarfQuest (469614) on Thursday October 07, 2010 @01:05PM (#33826500)

    He's not a scientist, but I'm fairly certain he got the idea from scientific circles.

    Actually, he is a Scientist. Has many published ideas. Geostationary satellites is one of his ideas. Just because you write Science Fiction doesn't cause them to throw you out of the guild.

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