Mineralogical characterization of Baptistina Asteroid Family: Implications for K/T impactor source |
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| Authors: | Vishnu Reddy Jorge M Carvano Daniela Lazzaro Tatiana A Michtchenko Michael J Gaffey Michael S Kelley Thais Mothé-Diniz Alvaro Alvarez-Candal Nicholas A Moskovitz Edward A Cloutis Erin L Ryan |
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| Institution: | aDepartment of Space Studies, Room 520, Box 9008, University of North Dakota, Grand Forks, ND 58202, USA;bObservatório Nacional (COAA), rua Gal. José Cristino 77, São Cristóvão, CEP20921-400 Rio de Janeiro, RJ, Brazil;cInstitute for Astronomy, Geophysics, and Atmospheric Sciences, University of São Paulo, Brazil;dDepartment of Space Studies, Room 518, Box 9008, University of North Dakota, Grand Forks, ND 58202, USA;eDepartment of Geology and Geography, Box 8149, Georgia Southern University, Statesboro, GA 30460, USA;fObservatório do Valongo, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil;gAlonso de Córdova 3107, Vitacura, Casilla, 19001, Santiago 19, Chile;hCarnegie Institution of Washington, Department of Terrestrial Magnetism, 5241, Broad Branch Road, Washington, DC 20008, USA;iDepartment of Geography, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba, Canada R3B 2E9;jDepartment of Astronomy, University of Minnesota, MN 55455, USA |
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| Abstract: | Bottke et al. Bottke, W.F., Vokrouhlicky, D., Nesvorný, D., 2007. Nature 449, 48–53] linked the catastrophic formation of Baptistina Asteroid Family (BAF) to the K/T impact event. This linkage was based on dynamical and compositional evidence, which suggested the impactor had a composition similar to CM2 carbonaceous chondrites. However, our recent study Reddy, V., Emery, J.P., Gaffey, M.J., Bottke, W.F., Cramer, A., Kelley, M.S., 2009. Meteorit. Planet. Sci. 44, 1917–1927] suggests that the composition of (298) Baptistina is similar to LL-type ordinary chondrites rather than CM2 carbonaceous chondrites. This rules out any possibility of it being related to the source of the K/T impactor, if the impactor was of CM-type composition. Mineralogical study of asteroids in the vicinity of BAF has revealed a plethora of compositional types suggesting a complex formation and evolution environment. A detailed compositional analysis of 16 asteroids suggests several distinct surface assemblages including ordinary chondrites (Gaffey SIV subtype), primitive achondrites (Gaffey SIII subtype), basaltic achondrites (Gaffey SVII subtype and V-type), and a carbonaceous chondrite. Based on our mineralogical analysis we conclude that (298) Baptistina is similar to ordinary chondrites (LL-type) based on olivine and pyroxene mineralogy and moderate albedo. S-type and V-type in and around the vicinity of BAF we characterized show mineralogical affinity to (8) Flora and (4) Vesta and could be part of their families. Smaller BAF asteroids with lower SNR spectra showing only a ‘single’ band are compositionally similar to (298) Baptistina and L/LL chondrites. It is unclear at this point why the silicate absorption bands in spectra of asteroids with formal family definition seem suppressed relative to background population, despite having similar mineralogy. |
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| Keywords: | Spectroscopy Asteroids composition Asteroids dynamics Impact processes Mineralogy |
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