DPS 42nd Meeting Abs..

02.05: Magnec Evidence for a Parally Differenated Carbonaceous Chondrite Parent Body and Possible Implicaons for Asteroid 21 LuteaAuthor Block: Benjamin Weiss 1 , L. Carporzen 1 , L. Elkins-Tanton 1 , D. L. Shuster 2 , D. S. Ebel 3 , J. Gaacceca 4 , R. P. Binzel 11 Massachuses Instute of Technology, 2 Berkeley Geochronology Center, 3 American Museum of Natural History, 4 CNRS/Universite Aix-Marseille, France.Presentaon Time: 10/4/2010 9:10 AM - 9:20 AMLocaon: Ballroom DAbstract: The origin of remanent magnezaon in the CV carbonaceous chondrite Allende has been a longstanding mystery. The possibility of a core dynamolike that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferenated. Here we report thatAllende's magnezaon was acquired over several million years (Ma) during metasomasm on the parent planetesimal in a >~20 microtesla field ~8-9 Ma aersolar system formaon. This field was present too recently and direconally stable for too long to have been the generated by the protoplanetary disk or youngSun. The field intensity is in the range expected for planetesimal core dynamos (Weiss et al. 2010), suggesng that CV chondrites are derived from the outer,unmelted layer of a parally differenated body with a convecng metallic core (Elkins-Tanton et al. 2010). This suggests that asteroids with differenatedinteriors could be present today but masked under chondric surfaces. In fact, CV chondrites are spectrally similar to many members of the Eos asteroid familywhose spectral diversity has been interpreted as evidence for a parally differenated parent asteroid (Mothe-Diniz et al. 2008). CV chondrite spectral andpolarimetric data also resemble those of asteroid 21 Lutea (e.g., Belskaya et al. 2010), recently encountered by the Rosea spacecra. Ground-basedmeasurements of Lutea indicate a high density of ~2.4-5.1 g cm -3 (Drummond et al. 2010), while radar data seem to rule out a metallic surface composion(Shepard et al. 2008). If Rosea spacecra measurements confirm a high density and a CV-like surface composion for Lutea, then we propose Lutea may bean example of a parally differenated carbonaceous chondrite parent body. Regardless, the very existence of primive achondrites, which contain evidence ofboth relict chondrules and paral melng, are prima facie evidence for the formaon of parally differenated bodies.02.06: Reconciling Giant Planet Formaon With the Origin and Impact History of the Parent Bodies of Differenated MeteoritesAuthor Block: Nader Haghighipour 1 , E. R. D. Sco 1 , G. J. Taylor 1 , D. O' Brien 21 Univ. of Hawaii, 2 Planetary Science Instute.Presentaon Time: 10/4/2010 9:20 AM - 9:30 AMLocaon: Ballroom DAbstract: The extraordinary number of different parent bodies of iron meteorite, and the dearth of asteroids and meteorites derived from the silicate mantlesand crusts of these objects is beer understood if these bodies accreted at 1-2 AU during the first 2 Myr when 26Al melted all ice-free planetesimals larger than20-km. It has been suggested that planetary embryos at 1-2 AU dynamically excited the differenated planetesimals and scaered their fragments into theasteroid belt where they were captured by planetary embryos. The scaering and accreon of planetesimals has occurred during the me that giant planets weregrowing. If the mescale for the formaon of giant planets is comparable with the me of the accreon of parent bodies of iron meteorites (e.g. as short as in therecent version of the core-accreon model), or if it is as small as suggested by the disk instability scenario, the perturbaon of growing giant planet(s) may affectthe scaering, collision, and accreon of planetesimals. We have studied these effects in order to compare the results with meteoric data to constrain the meof giant planet formaon. We have numerically integrated the moons, collisions, and accreon of a large baery of planetesimals and planetary embryos in theregion between 0.5 and 4 AU during the growth of two giant planets in orbits of Jupiter and Saturn. Results indicate that the perturbaons of growing giantplanets decrease the efficiency of planetesimals scaering when these objects grow to approximately 50 Earth-masses. For larger values of mass, this efficiencydrops drascally suggesng that very short mescales for the growth of giant planets may not be favorable for models of the formaon of the parent bodies ofiron meteorites. We present the results of our simulaons and discuss their implicaons for the me of giant planet formaon.02.07: Formalism for the Impact Rate of Comets on the Inner Satellites and Rings of the Giant PlanetsAuthor Block: Henry C. (Luke) Dones 1 , E. B. Bierhaus 2 , K. J. Zahnle 3 , D. Nesvorný 1 , H. F. Levison 1 , C. R. Chapman 11 Southwest Research Inst., 2 Lockheed Marn, Space Exploraon Systems, 3 NASA Ames Research Center.Presentaon Time: 10/4/2010 9:30 AM - 9:40 AMLocaon: Ballroom DAbstract: Determining the rate at which eclipc comets have struck the satellites of the giant planets throughout the history of the Solar System is importantfor understanding the formaon and evoluon of satellites and planetary rings (e.g., Charnoz et al. 2009, Barr et al. 2010). Impact rates are oen calculated usingÖpik's equaons (Shoemaker and Wolfe 1982), which give the impact probability of a small body with a satellite in terms of the small body's pericenter distance(q), orbital eccentricity (e), and inclinaon (i). Zahnle et al. (1998, 2003) performed Monte Carlo simulaons that implement Öpik's equaons and have tabulatedimpact rates for a wide variety of satellites. These simulaons assume a distribuon of present-day encounter speeds (U) based on simulaons by Levison andDuncan (1997). However, encounter speeds probably would have been larger during the era of heavy bombardment (Charnoz et al. 2009). We have developed ananalycal approach to calculate satellite impact rates, relave to the rate on their parent planet, as a funcon of U. Our approach assumes that the orbitaldistribuon of eclipc comets that encounter a planet is isotropic in the frame of the planet (Levison et al. 2000). Our results agree well with those of Zahnle etal. (1998, 2003), and with numerical integraons carried out with the 'scaer3' roune in STARLAB (hp://www.sns.ias.edu/~starlab/). We thank the NASA CDAPand Origins programs for support.··········Barr, A.C., Canup, R.M., Nature Geoscience 3, 164-167 (2010)Charnoz, S., et al., Icarus 199, 413-428 (2009)Levison, H.F., Duncan, M.J., Icarus 127, 13-32 (1997)Levison, H.F., et al., Icarus 143, 415-420 (2000)Shoemaker, E.M., Wolfe, R.F., in Satellites of Jupiter, pp. 277-339 (1982)Zahnle, K., Dones, L., Levison, H.F., Icarus 136, 202-222 (1998)Zahnle, K., et al., Icarus 163, 263-289 (2003)02.08: Constraints On Satellite Formaon From Io's Low InclinaonAuthor Block: Douglas P. Hamilton 1 , C. Philpo 11 Univ. of Maryland.Presentaon Time: 10/4/2010 9:40 AM - 9:50 AMLocaon: Ballroom DAbstract: The Laplace resonances between the satellites Io, Europa, and Ganymede has had a profound effect on the evoluon of the jovian system. In itscurrent configuraon, the resonances enable some of the spin energy of Jupiter to be tapped to power the volcanos on Io. But when, and equally importantly, atwhat distance from Jupiter did this resonance first originate? Were the satellites pushed together by dal forces or by an earlier phase of inward migraon? Havethe satellites ever been deeper in resonance than they are today? Some of these quesons can be addressed by considering clues contained in the current orbital