[meteorite-list] How Long from Asteroid to Meteorite?
From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 12 Jul 2010 21:59:13 -0500 Message-ID: <A49B9CD867AC40A4882DCAA532259157_at_ATARIENGINE2> Eric, List, all, > Asteroids are traveling at super high velocity when they impact... The most common collision in a group of objects with similar orbits is with two objects with similar orbits. Oh, yes, in the movies it's always something that comes racing out of far nowhere and -- Smack! But in the real world, it's more like jostling each other. I mean, the biggest threat to Earth would be something in an orbit similar to our own, right? We want our orbit to ourselves!. So it is for asteroids. What is the most likely speed of that kind of collision? It's the same speed that it would take to go from asteroid to asteroid. Now, in SciFi stories, folks are always hopping from one asteroid to another in dinky little jumper spaceships, but in fact most transfer orbits between asteroids require a delta-vee of 4000 m/sec to 5000 m/sec. If you calculate Hohmann orbits between Ceres and Vesta, Pallas and Vesta, Pallas and Ceres, they all fall in that range. That means it's twice as hard as taking off from the Moon (or landing on the Moon) or about half the effort of getting to low Earth orbit. If one asteroid wanders into the path of another or intersects its orbit when it's there, the impact velocities between them could be as low as a few thousand meters per second or as high as six to eight thousand meters per second, depending on the specifics of the encounter. On the other hand, here at the bottom of a deep gravity well, even a standstill object is going to pick up 11,200 meters per second falling in, plus any encounter velocity it might have started with. In other words, we get whacked but good with an average encounter speed of 20,000+ meters per second So oddly enough, most asteroidal collisions are gentler than collisions with the Earth. They're more than enough to do real damage of course, including disrupting whole bodies, but that's because asteroids are weaker (except for solid irons). As for the speed of fragments "blown off" by a collision, they depart at speeds less than the collision speed that spawned them. Statistically, at about collision speed times the square root of two, for an average. There is a small chance for more energetic collisions. That's when one object has an odd orbit: high eccentricity orbits and high angle collisions, retrograde versus prograde, all sorts of odd things, but the point is that we call'em "odd" because they're infrequent when compared to ALL collisions. Fragments generated at the very inner edge of the asteroid zone can get here in 50,000 to 80,000 years, stuff from the main belt in a few to ten million years, stuff from the outer asteroid zone (type D and P) much longer. But time is even longer than space is big... So they tell me. Sterling K. Webb -------------------------------------------------------------------------------- ----- Original Message ----- From: "Meteorites USA" <eric at meteoritesusa.com> To: <meteorite-list at meteoritecentral.com> Sent: Monday, July 12, 2010 5:02 PM Subject: [meteorite-list] How Long from Asteroid to Meteorite? > Hi Greg S., Richard, List, > > Greg's question about the furthest known celestial body from which we > have a meteorite is very interesting! And it brings up another very > interesting question related to distance... > > If we're not sure of the furthest asteroid or comet we've got > meteorites from, can we at least figure out how long it takes > meteorites to get here from the asteroid belt once asteroids collide? > We know meteorites come from a variety of planetary and asteroid > bodies, and even some are suspected cometary debris. But... > > I've always wondered how long it would take a piece of asteroid debris > to impact our planet after an asteroid collision. > > Asteroids are traveling at super high velocity when they impact, > creating massive explosive power comparable to multiple nuclear > explosions at once. Wouldn't that launch debris in ALL directions at > cosmic velocity? If this ejecta debris is moving at 15,000 to 25,000 > MPH how long would it take to reach our planet from the asteroid belt? > Would it slow considerably between there and here given the > gravitational forces exerted by Mars, Jupiter, the Moon, or even our > planet? Would most of the debris get caught by other planets, or even > in stable orbits around the Sun? How do you figure orbits of this > smaller debris which come from these collisions when you can't even > see it? > > I know, sorry for all the questions... but I want to know darnit! ;) > > Regards, > Eric > > > > On 7/12/2010 2:25 PM, Richard Kowalski wrote: >> Hi Greg. >> >> You probably will not be able to get a definitive answer to this one. >> Meteorite parent bodies are from asteroids and the most likely >> mechanism to inject asteroids and their fragments into orbits that >> intersect the earth is perturbations by Jupiter. This places most >> asteroidal meteorites parent bodies in the outer Main Belt. >> >> As far as I know, there are no meteorites that have all the expected >> properties that a cometary meteorite should have, so that makes the >> Main Belt the most distant source of meteorites currently known. >> >> If a cometary meteorite is discovered, it's parent ultimately would >> be the Oort Cloud, so that would change "The most distant" record >> holder instantly. >> >> Campins and Swindle presented a summary on what properties a cometary >> meteorite should have at the 39th Lunar and Planetary Science >> Conference in 2008. It can be read here: >> http://www.lpi.usra.edu/meetings/LPSC98/pdf/1004.pdf >> >> >> >> -- >> Richard Kowalski >> Full Moon Photography >> IMCA #1081 >> >> >> --- On Mon, 7/12/10, Thunder Stone<stanleygregr at hotmail.com> wrote: >> >> >>> From: Thunder Stone<stanleygregr at hotmail.com> >>> Subject: [meteorite-list] What Meteorite is 'From' the farthest >>> location from the Earth? >>> To: meteorite-list at meteoritecentral.com >>> Date: Monday, July 12, 2010, 1:17 PM >>> >>> Hi List: >>> >>> I was wondering if it is know what meteorite(s) is from (or >>> was created) at the farthest point from Earth? I know they >>> come from the asteroid belt and perhaps from comets, but >>> wouldn't it be really neat to have a meteorite that was >>> formed or (from) the farthest distance from Earth in your >>> hand: I think it would. >>> >>> Greg S. >>> >>> _________________________________________________________________ >>> Hotmail is redefining busy with tools for the New Busy. Get >>> more from your inbox. >>> http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_2 >>> ______________________________________________ >>> Visit the Archives at >>> http://www.meteoritecentral.com/mailing-list-archives.html >>> Meteorite-list mailing list >>> Meteorite-list at meteoritecentral.com >>> http://six.pairlist.net/mailman/listinfo/meteorite-list >>> >>> >> >> >> ______________________________________________ >> Visit the Archives at >> http://www.meteoritecentral.com/mailing-list-archives.html >> Meteorite-list mailing list >> Meteorite-list at meteoritecentral.com >> http://six.pairlist.net/mailman/listinfo/meteorite-list >> >> > ______________________________________________ > Visit the Archives at > http://www.meteoritecentral.com/mailing-list-archives.html > Meteorite-list mailing list > Meteorite-list at meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list Received on Mon 12 Jul 2010 10:59:13 PM PDT |
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