Binary Asteroid In Jupiter's Orbit May Be Icy Comets

[zavvy]

<b>Binary Asteroid In Jupiter's Orbit May Be Icy Comets</b><br /><br />LINK<br /><br />A bound pair of icy comets similar to the dirty snowballs circling outside the orbit of Neptune has been found lurking in the shadow of Jupiter. <br /><br />Astronomers at the University of California, Berkeley, working with colleagues in France and at the Keck Telescope in Hawaii, have calculated the density of a known binary asteroid system that shares Jupiter's orbit, and concluded that Patroclus and its companion probably are composed mostly of water ice covered by a patina of dirt. <br /><br />Because dirty snowballs are thought to have formed in the outer reaches of the solar system, from which they are occasionally dislodged and end up looping closer to the sun as comets, the team suggests that the asteroid probably formed far from the sun. It most likely was captured in one of Jupiter's Trojan points - two eddies where debris collects in Jupiter's orbit - during a period when the inner solar system was intensely bombarded by comets, around 650 million years after the formation of the solar system. <br /><br />If confirmed, this could mean that many or most of the probably thousands of Jupiter's Trojan asteroids are dirty snowballs that originated much farther from the sun and at the same time as the objects now occupying the Kuiper Belt. <br /><br />"It's our suspicion that the Trojans are small Kuiper Belt objects," said study leader Franck Marchis, a research astronomer at UC Berkeley. <br /><br />Marchis and colleagues from the Institut de Mécanique Céleste et Calculs d'Éphémérides (IMCCE) at the Observatoire de Paris and from the W. M. Keck Observatory report their findings in the Feb. 2 issue of Nature. <br /><br />The team's conclusion adds support to a recent hypothesis about the evolution of the orbits of our solar system's largest planets, Jupiter, Saturn, Uranus and Neptune, put forth b

 

[mikeemmert]

Capture into a Lagrange point (or Lagrange stability zone) is not impossible, but it is highly unlikely. The scenario presented (a KBO captured into a Jupiter Lagrange point) involves high flyby speed. There would most likely have to be several flybys (past Jupiter) to slow it down. Any binary in this scenario would likely get ripped apart.<br /><br />I think Patroclus formed in the Jupiter Lagrage zone and is still there. <br /><br />Most Lagrange zones are empty or nearly so. Jupiter is the exception. It's Lagrange zones are crowded with huge asteroids. I think numerous flythroughs of the Lagrange zones by asteroids which have previously flown past Jupiter pumped energy into the zones which prevented the asteroids there from coalescing into one body or a single binary. That process in most other cases where evidence has been left has resulted in the ejection of whatever was in the Lagrange zones.

 

[dmjspace]

Simply more evidence that there is little difference between what we typically call asteroids and comets...<br /><br />See the Deep Impact thread for more discussion on the question of whether comets and asteroids differ significantly.

 

[yevaud]

Warning - that thread will shortly be locked (I'm surprised they haven't done so yet) - it's over 600 posts. You might want to begin a new one. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[bonzelite]

why does the article use <i>dirty snowball</i> so profusely when that is now a highly doubted idea?

 

[dmjspace]

bonzelite said: <font color="yellow"> why does the article use dirty snowball so profusely when that is now a highly doubted idea? </font><br /><br />Old habits are hard to break, I guess.<br /><br />Perhaps when the model evolves to "essentially homogenous rock-like substance with a barely perceptible dusting of snowy particulate," we can finally consider this paradigm shift complete.<br /><br />But until that happens, looks like we'll have to continue to suffer the snowball imagery as more people move up the learning curve. <img src="/images/icons/wink.gif" />

 

[bonzelite]

then it makes the article read like dated science fiction. <br /><br />suffer, indeed. and that is merely one thing.

 

[mikeemmert]

Well, they locked the Deep Impact thread. 657 posts! Whew!!!<br /><br />I missed that thread because I was busy doing other things and the few posts I read on it had little to do with asteroid and comet composition. Most of it was "Wow! Look at the neat explosion!"<br /><br />I now believe that failure to follow that thread was a bad decision. Life is full of bad decisions. Oh, well...<br /><br />Anyway, I think Patroclus is an original Lagrange object and the successful measurement of it's density shows that Jupiter's orbit is where water ice started condensing out of the solar nebula on a large scale.<br /><br />I have to go out this afternoon and see to my car. No internet posting can trump that, this is a good decision. I hope to see more information when I get back.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Perhaps when the model evolves to "essentially homogenous rock-like substance with a barely perceptible dusting of snowy particulate," we can finally consider this paradigm shift complete. <p><hr /></p></p></blockquote><br /><br />Well, actually comets tend to be very dark on their surfaces, so "dusting of snowy particulate" isn't likely to be much more accurate. But the dirty snowball idea has held on in the popular press in large part because it's got a name that the average Joe finds appealing. "Dirty snowball" is a fun concept in many ways. I mean, who hasn't enjoyed throwing a snowball? And this time of year, they get dirty indeed. <img src="/images/icons/wink.gif" /> So it has a certain asthetic appeal to a lot of people.<br /><br />One of the biggest problems with analogies like that is that they become sound bites and pretty soon the general public hears only the analogy -- sometimes to the extent that the general public grossly misunderstands what was originally meant by the analogy. (This isn't one of those cases, IMHO, but it does happen.) People like there to be simple answers, and unanimity in the science community. Unfortunately, there are rarely simple answers, and the science community is rarely unanimous. This disconnect between the public expectation and the actual reality does cause problems from time to time, and the fact that most people have virtually no science education only makes the problem worse. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Most Lagrange zones are empty or nearly so. Jupiter is the exception.<p><hr /></p></p></blockquote><br /><br />This is probably because Jupiter is so incredibly much bigger than the other planets. However, it's probably a bit early to be sure of other lagrange points not having much stuff in them. Objects in some of the more remote lagrange points, such as those around Neptune, are difficult to detect, so it's hard to be sure of their absence.<br /><br />An interesting case study for this is the Saturn system, though. There are lagrangian relationships throughout its satellites, and studying these interactions should be very useful for understanding the larger-scale relationships between planets. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[mikeemmert]

There are no snowballs in Texas (I'm jealous).

 

[mikeemmert]

Here's the wikipedia article on Lagrangian points. Pretty interesting.<br /><br />"<font color="yellow">In the Sun–Jupiter system several thousand asteroids, collectively referred to as Trojan asteroids, are in orbits around the Sun–Jupiter L4 and L5 points. Other bodies can be found in the Sun–Saturn, Sun–Mars, Jupiter–Jovian satellite, and Saturn-Saturnian satellite systems. There are no known large bodies in the Sun–Earth system's Trojan points, but clouds of dust surrounding the L4 and L5 points were discovered in the 1950s. Clouds of dust, called Kordylewski clouds, even fainter than the notoriously weak gegenschein, are also present in the L4 and L5 of the Earth–Moon system.<br /><br />The Saturnian moon Tethys has two smaller moons in its L4 and L5 points, Telesto and Calypso. The Saturnian moon Dione also has two Lagrangian co-orbitals, Helene at its L4 point and Polydeuces at L5. The moons wander azimuthally about the Lagrangian points, with Polydeuces describing the largest deviations, moving up to 32 degrees away from the Saturn–Dione L5 point. Tethys and Dione are hundreds of times more massive than their "escorts" (see the moons' articles for exact diameter figures; masses are not known in several cases), and Saturn is far more massive still, which makes the overall system stable.<font color="white">".<br /><br />It's best to go to the link, because it has links to all these things. The objects in the other Lagrange points besides the Sun/Jupiter and Saturn/moon of Saturn Lagrange points are all tiny. A couple of candidates have been found in the Sun/Neptune Lagrange zones, or areas, but it has not been proven that they are actually in a Lagrange relationship. <br /><br />The hold that two objects have on the third in an L4 or L5 Lagrange situation is quite a bit more tenuous than most people seem to believe. To escape from a Sun/Earth Lagrange point only takes a little over 700 meters pe</font></font>