How To Build A Moon From Planetary Rings

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PostTue Dec 04, 2012 1:39 am » by -Marduk-


Interesting read...


Solar System's Moons May Have Emerged from Long-Gone Planetary Rings


Ancient, Saturn-like ring systems may have acted as assembly lines for natural satellites. "If you wish to make an apple pie from scratch," as Carl Sagan once said, "you must first invent the universe." And if you wish to make a moon from scratch, according to new research, you must first create planets with rings (after inventing the universe, of course).

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Earth’s moon may have emerged from a long-vanished ring system, much like the rings still encircling Saturn – and the same goes for many of the satellites orbiting the other planets. The bulk of the solar system’s regular satellites—those moons that stick close to their planets in roughly equatorial orbits—formed this way, rather than taking shape simultaneously with the planets as a direct result of planet formation, French astrophysicists have concluded. The researchers reported their findings in the November 30 issue of Science. “It’s fundamentally the same process that gave birth to the moon and to the satellites of the giant planets, and that’s the spreading of rings,” says astrophysicist Aurélien Crida of the University of Nice–Sophia Antipolis and the Observatory of Côte d’Azur in France, who co-authored the study with Sébastien Charnoz of the University of Paris–Diderot. Through theoretical modeling, the researchers found that the moon-formation action begins at the edge of a planetary ring, where a satellite can take shape without being shredded by the gravitational pull of the planet. There, moonlets coagulate from the ring material before migrating outward. As the ring system spits out moonlet after moonlet, the small objects merge to form larger moons, which may merge in turn as they spiral outward from the planet.

The idea of a moonlet assembly line differs from the standard conception of satellite birth, in which moons condense along with their host planet from a swirling cloud of dust and gas, much like the planets themselves are thought to have taken shape around the nascent sun. The solar-system-in-miniature concept seems to work well for the largest moons, such as Jupiter’s four so-called Galilean satellites, but the retinue of smaller moons circling the other giant planets “have so far been considered a by-product,” Crida says. The new hypothesis seems to explain a key commonality among the regular satellites of Saturn, Uranus and Neptune – namely, that moons farther from their respective planets tend to have larger masses than their closer-in neighbors. Like a snowball rolling downhill, the coalescing moons would grow larger and larger as they drift farther from the planet and its rings, undergoing progressively more mergers along the way. The end result is a neatly ordered satellite system, with small moons on the inside built from few moonlets and large moons farther out built from numerous moonlets. “I think the best thing about this work is that they explain this link between the mass of the moon and the orbital distance, which was known before but not understood,” says planetary scientist David Nesvorny of the Southwest Research Institute in Boulder, Colo., who did not contribute to the new research. “If you had asked me a few years ago, I would think of our moon’s formation and the formation of the satellites of the outer planets differently,” he adds. “This theory puts things on common ground.”

Planetary scientists generally accept that a giant impact into the newly formed Earth ejected a huge cloud of material that became the moon. In Crida and Charnoz’s conception, that ejecta first flattened into a ring around the planet, which then spread out and coagulated into the moon. But unlike Saturn’s ring, which would have leaked out numerous moonlets to form several moons, Earth’s relatively massive ring would have poured all its material into one large satellite before dissipating. “It spreads very fast,” Crida says of Earth’s hypothesized ring. “And if it spreads fast, only one moon has time to form.” But the new hypothesis is not without its problems. First, it does not seem to apply to the satellites of Jupiter, which do not obey the same mass-to-distance correlation of the other moon systems. Crida notes that Jupiter was the first planet to form and may have coalesced under different conditions. “I was a bit disappointed to see that Jupiter did not fit the same distribution, but not too surprised,” he says. And then there is the obvious question: if extensive, Saturn-like ring systems once adorned Neptune and Uranus, where are they now? “It’s not that easy to remove them over time,” Nesvorny says. “There is a link that’s missing that needs to be understood.”

The French researchers concede that the fate of the rings is an open question. “I don’t know why Uranus and Neptune don’t have the rings anymore,” Crida says. “We have a few ideas, but nothing too convincing. Some people can see that as a weakness of our mechanism, because indeed where are the rings now? But I think we can find good reasons for the disappearance of the rings, and the satellites remain as the smoking gun."

http://www.scientificamerican.com/artic ... turn-rings
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PostTue Dec 04, 2012 1:57 am » by Kinninigan


:look:

What happened to marduk?






Giant Impact Scenario May Explain the Unusual Moons of Saturn

ScienceDaily (Oct. 17, 2012) — Among the oddities of the outer solar system are the middle-sized moons of Saturn, a half-dozen icy bodies dwarfed by Saturn's massive moon Titan. According to a new model for the origin of the Saturn system, these middle-sized moons were spawned during giant impacts in which several major satellites merged to form Titan.

Erik Asphaug, professor of Earth and planetary sciences at the University of California, Santa Cruz, will present this new hypothesis October 19 at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nevada. Asphaug and his coauthor, Andreas Reufer of the University of Bern, Switzerland, also describe their model in detail in a paper to be published in Icarus (in press).

Asphaug and Reufer propose that the Saturn system started with a family of major satellites comparable to the four large moons of Jupiter (known as the Galilean moons, discovered by Galileo in 1610). The Galilean moons account for 99.998 percent of the mass in Jupiter's satellite system; although it has dozens of small satellites, Jupiter has no middle-sized moons. The new model may explain why the two systems are so different.

"We think that the giant planets got their satellites kind of like the Sun got its planets, growing like miniature solar systems and ending with a stage of final collisions," Asphaug said. "In our model for the Saturn system, we propose that Titan grew in a couple of giant impacts, each one combining the masses of the colliding bodies, while shedding a small family of middle-sized moons."

Earth is thought to have undergone a similar kind of giant impact, in which our planet gained the last ten percent of its mass and spawned the moon. Just as our moon is thought to be made out of material similar to Earth's rocky mantle, the middle-sized moons of Saturn are made of material similar to Titan's icy mantle, Asphaug said.

"Our model explains the diversity of these ice-rich moons and the evidence for their very active geology and dynamics," he said. "It also explains a puzzling fact about Titan, in that a giant impact would give it a high orbital eccentricity."

Asphaug and Reufer used computer simulations to study the giant impact scenario, and they found that mergers of satellites the size of the Galilean moons can liberate ice-rich spiral arms, mostly from the outer layers of the smaller of the colliding moons. Gravitational clumping of the spiral arms then leads to the formation of clumps with sizes and compositions that resemble Saturn's middle-sized moons.

"These satellite collisions are a regime that is not very well understood, so the modeling opens up new possibilities in general for planet formation," Reufer said.

The proposed mergers might have occurred as the final act in the process of satellite formation. Alternatively, Saturn may have had a stable system of Galilean-like satellites that was later disrupted by the possibly chaotic migration of the giant planets, as described in the popular "Nice model" of the solar system. A late origin has the advantage of explaining some of the most striking features of the Saturn system.

"What makes the Saturn system so beautiful and unique could be its youth," Asphaug said. "While we don't have a preferred timeframe for this origin scenario to play out, it could have happened recently if something came along to destabilize the Saturn system, triggering the collisional mergers that formed Titan. This 'something' could have been the close passage of a marauding Uranus and Neptune, which is part of the Nice model."

Asphaug acknowledged a couple of dynamical issues raised by the new model. The clumps spawned from the giant impacts might get swept up into the accretion of Titan, rather than evolving into separate moons with their own stable orbits. Additional simulations of the dynamical evolution of the complicated, accreting system are needed to further explore and validate the model. But Asphaug said new data from NASA's Cassini mission on the geophysics of Saturn's moons will provide the ultimate tests.

"Our model makes strong predictions for how Titan was assembled, what the middle-sized moons are made of, and how they started out as rapidly spinning clumps of ice-rich material," he said. "So it's testable. These little moons could provide the clues telling us what happened, and when."

This research was funded by NASA, the University of California, and the Swiss National Science Foundation.

Note: A video simulation can be found at: http://vimeo.com/50778094









http://www.sciencedaily.com/releases/20 ... 154848.htm










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PostTue Dec 04, 2012 1:59 am » by Slith


Apparently Marduk has been transformed
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PostTue Dec 04, 2012 2:04 am » by -Marduk-


Kinninigan wrote: :look:

What happened to marduk?

I needed a Tapetenwechsel...hardly earth-shattering.

Nice post btw, Kin.
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PostTue Dec 04, 2012 2:05 am » by domdabears


God dammit, Gal
I wanna be a Warhol
Displayed on your wall
Still hung up on you

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PostTue Dec 04, 2012 2:05 am » by Kinninigan


GALVATRON wrote:
Kinninigan wrote: :look:

What happened to marduk?

I needed a Tapetenwechsel...hardly earth-shattering.

Nice post btw, Kin.



irony is saturn can transform into a sun....




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PostTue Dec 04, 2012 2:12 am » by -Marduk-


Slith wrote:Apparently Marduk has been transformed

CHKK CHRR CHRRKK chee choo choo choo chuh

HAHAHA
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PostTue Dec 04, 2012 2:18 am » by -Marduk-


Kinninigan wrote:irony is saturn can transform into a sun....

:cheers:

Finally, someone who actually READ Arthur C Clarke's book 2001 and not only watched the movie.

:clapper:
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PostTue Dec 04, 2012 2:19 am » by Kinninigan


GALVATRON wrote:
Kinninigan wrote:irony is saturn can transform into a sun....

:cheers:

Finally, someone who actually READ Arthur C Clarke's book 2001 and not only watched the movie.

:clapper:



i know my shiz-nit about saturn!



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PostTue Dec 04, 2012 2:29 am » by Slith


GALVATRON wrote:
Slith wrote:Apparently Marduk has been transformed

CHKK CHRR CHRRKK chee choo choo choo chuh

HAHAHA


Oh shit. Remember watching that with my kids. CHKK CHRR CHRRKK chee choo choo choo chuh is so bang on.

Lolz :flop:
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