Re: [meteorite-list] Minor Planet families
Hi Graham: I am far from an asteroid dynamics person, but many (but not all) asteroid families tend to share compositional similarities and so may very well be remnants of larger objects that have recently been broken up in a collisional event. The families are usually (but not always) named for their largest member. This is important in that if members of these families are in the right place in the asteroid belt, their members' orbits may be perturbed over time into Earth-crossing orbits and then Earth-impacting orbits, so that they may be the sources of some of the meteorites we see. Connecting individual asteroids to classes of meteorites is another story! Larry Hi Graham, Thanks Robso the named groups at the moment just represent similar orbiting asteroids which over time have settled into that orbit over time after they were nudged from the asteroid belt ... The asteroid belt is a pretty broad term. Between the orbits of Mars and Jupiter are over a dozen major named families (e.g. Cybele, Eos, Eunomia, Flora, Hilda, Hungaria, Koronis, Maria, Nysa, Phocaea, Themis, Main Belt I, Main Belt II, Main Belt IIb, Main Belt IIIa, Main Belt IIIb). It's not unlike the naming of different meteorite groups: just as all H-chondrites share common features, each asteroid family has a particular combination of orbital elements (semi-major axis and inclination are the primary determinants of a minor planet's family) that distinguish it from its neighbors. --Rob __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Minor Planet families
To elaborate on Rob's and Larry's comments, a further complication is that asteroids are placed into classes based on two major criteria: orbit and composition. The orbital classifications (like Apollo) are mainly determined by ratios of specific orbital elements. The compositional classes are primarily determined by spectral characteristics, and are often the classes of most interest to meteorite enthusiasts, given the ability to connect many meteorites to specific asteroid spectral families (e.g. V type asteroids are associated with HED meteorites). Only in a handful of cases do we have a recovered orbit for a meteorite fall, allowing for the possibility of recognizing the parent body's orbital classification as well. Chris *** Chris L Peterson Cloudbait Observatory http://www.cloudbait.com On 2/26/2013 4:26 AM, lebof...@lpl.arizona.edu wrote: Hi Graham: I am far from an asteroid dynamics person, but many (but not all) asteroid families tend to share compositional similarities and so may very well be remnants of larger objects that have recently been broken up in a collisional event. The families are usually (but not always) named for their largest member. This is important in that if members of these families are in the right place in the asteroid belt, their members' orbits may be perturbed over time into Earth-crossing orbits and then Earth-impacting orbits, so that they may be the sources of some of the meteorites we see. Connecting individual asteroids to classes of meteorites is another story! Larry __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Minor Planet families
Thanks to everybody for their enlightening posts on this questionanswering many aspects that I had wondered aboutan interesting thread. Graham On Tue, Feb 26, 2013 at 2:59 PM, Chris Peterson c...@alumni.caltech.edu wrote: To elaborate on Rob's and Larry's comments, a further complication is that asteroids are placed into classes based on two major criteria: orbit and composition. The orbital classifications (like Apollo) are mainly determined by ratios of specific orbital elements. The compositional classes are primarily determined by spectral characteristics, and are often the classes of most interest to meteorite enthusiasts, given the ability to connect many meteorites to specific asteroid spectral families (e.g. V type asteroids are associated with HED meteorites). Only in a handful of cases do we have a recovered orbit for a meteorite fall, allowing for the possibility of recognizing the parent body's orbital classification as well. Chris *** Chris L Peterson Cloudbait Observatory http://www.cloudbait.com On 2/26/2013 4:26 AM, lebof...@lpl.arizona.edu wrote: Hi Graham: I am far from an asteroid dynamics person, but many (but not all) asteroid families tend to share compositional similarities and so may very well be remnants of larger objects that have recently been broken up in a collisional event. The families are usually (but not always) named for their largest member. This is important in that if members of these families are in the right place in the asteroid belt, their members' orbits may be perturbed over time into Earth-crossing orbits and then Earth-impacting orbits, so that they may be the sources of some of the meteorites we see. Connecting individual asteroids to classes of meteorites is another story! Larry __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Minor Planet families
Graham and list, For some easy reading on this subject I highly recommend Meteorites and Their Parent Bodies, authored by Harry Y. McSween, Jr.; specifically chapter 8, 'A Space Odyssey'. By discussing impact age, orbit properties, orbital resonance (mean-motion and secular) and escape hatches Mr. McSween does an excellent job outlining how meteorites make their way from the asteroid belt to Earth. Michael in so. Cal. On Tue, Feb 26, 2013 at 7:32 AM, Graham Ensor graham.en...@gmail.com wrote: Thanks to everybody for their enlightening posts on this questionanswering many aspects that I had wondered aboutan interesting thread. Graham __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Minor Planet families
Hi Graham, Thanks Robso the named groups at the moment just represent similar orbiting asteroids which over time have settled into that orbit over time after they were nudged from the asteroid belt ... The asteroid belt is a pretty broad term. Between the orbits of Mars and Jupiter are over a dozen major named families (e.g. Cybele, Eos, Eunomia, Flora, Hilda, Hungaria, Koronis, Maria, Nysa, Phocaea, Themis, Main Belt I, Main Belt II, Main Belt IIb, Main Belt IIIa, Main Belt IIIb). It's not unlike the naming of different meteorite groups: just as all H-chondrites share common features, each asteroid family has a particular combination of orbital elements (semi-major axis and inclination are the primary determinants of a minor planet's family) that distinguish it from its neighbors. --Rob __ Visit the Archives at http://www.meteorite-list-archives.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
