Last

rasc.ca

insidethisissue - The Royal Astronomical Society of Canada

cause and true scope of sickness remain unclear. Meteorite fragmentsprovisionally typed as an H4-5 chondrite [3] were found surroundingthe crater [4].Fireball Kinematics and Energetics Analysis: Airwaves from thisevent were detected at infrasound stations in Bolivia and Paraguay andat least two seismic stations in Peru and Bolivia. Preliminary analysisof these data tentatively suggests that the fireball producing the impactcrater emanated from a radiant with azimuth ~ 60°, altitude ~ 50°.Interpretation of the airwave information combined with numericalmodeling of the entry/impact suggests the initial meteoroid hadan entry velocity below 17 km/s and was initially ~10 4 kg in mass,corresponding to an object 1m in radius. The initial energy is estimatedto be 0.15 – 0.4 kilotons TNT, with ~1% of this energy remaining to formthe impact crater. Modeling also suggests that the impact velocity at thecrater was hypersonic with a probable range from 1.5 – 3 km/s and thatthe very high altitude of the impact location (3.8 km) contributed to thesubstantial size of the crater by ensuring the meteoroid had not slowedsubstantially before impact.Discussion: Recent examples of meteorite falls producing penetrationcraters include the Sikhote-Alin iron meteorite shower of 1947 [5], theJilin chondrite fall of 1976 [6], the Sterlitamak iron of 1990 [7], and mostrecently the Kunya-Urgench chondrite in 1998 [8]. The Carancas crater,however, is the largest documented crater produced by an observedchondrite fall and is comparable to the largest penetration cratersproduced by the Sikhote-Alin fall. Based on impact scaling relations andcomparisons to other events, we estimate that the impacting meteoritewas 2-5 tonnes and a portion of this mass is likely buried at a depth> 5m in the SW corner beneath the existing flooded crater floor, mostlikely as a series of fragments rather than a single consolidated body.References:[1] Macedo, L. and Machare, J. 2007, The Carancas Meteorite Fall, 15Sept. 2007 Official INGEMMET initial report.[2] Carroll, R. 2007, The Guardian UK, September 18 “Peru meteoritecrash causes mystery illness”[3] Farmer, M., personal communication, 2007 October 15[4] Blanco Cazas, M. 2007, “Informe Laboratorio de Rayos X — FRX-DRX”[5] Krinov, E.L. 1966, Giant Meteorites, Pergamon Press, 395 pp[6] Joint Investigation Group, Kirin meteorite shower 1977, ScientiaSinica, 20: 502-512[7] Petaev, M.I., Kisarev, Y.L., and four others 1991, LPI ConferenceAbstracts 22, 1059[8] Mukhamednazarov, S. 1999, Astronomy Letters, 25, 117-118Embedded Star Clusters and the Formation of the Oort CloudIII: Evolution of the Inner Cloud During the Galactic Phase. R.Brasser 1 , M.J. Duncan 2 , and H.F. Levison 3 1 Dept. of Phys. Sciences, U. ofToronto at Scarborough, Toronto ON M1C 1A4 (brasser_astro@yahoo.com); 2 Dept. of Phys. & Astron., Queen’s U., Kingston, Ont.; 3 SouthwestResearch Institute, Boulder, Col., USA.Simulations have been performed where some of the inner Oort clouds ofBrasser et al. (2006), generated while the Sun was in its embedded birthcluster, were resumed in the current galactic environment to determinewhether or not the inner cloud (defined as comets having semi-majoraxis a

More magazines by this user
Similar magazines