Space weathering of small Koronis family members |
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| Authors: | Cristina A Thomas Andrew S Rivkin David E Trilling Jennifer A Grier |
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| Institution: | 1. Institute of Astronomy, Charles University, Prague, V Hole?ovi?kách 2, 18000 Prague 8, Czech Republic;2. Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France;1. Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklos Astronomical Institute, H-1121 Budapest, Konkoly Thege Miklós út 15-17, Hungary;2. Research Centre for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, H-1112 Budapest, Budaörsi út 45, Hungary;3. International Meteorite Collectors Association (IMCA#6251), H 9024 Gy?r, Lahner u 1, Hungary;4. Geographical Institute, H-1112 Budapest, Budaörsi út 45, Hungary;5. Wigner Research Centre for Physics, H-1121 Budapest, Thege Miklós út 29-33, Hungary;6. ELTE Department of Environmental and Landscape Geography, Hungary |
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| Abstract: | The space weathering process and its implications for the relationships between S- and Q-type asteroids and ordinary chondrite meteorites is an often debated topic in asteroid science. Q-type asteroids have been shown to display the best spectral match to ordinary chondrites (McFadden, L.A., Gaffey, M.J., McCord, T.B. 1985]. Science 229, 160–163). While the Q-types and ordinary chondrites share some spectral features with S-type asteroids, the S-types have significantly redder spectral slopes than the Q-types in visible and near-infrared wavelengths. This reddening of spectral slope is attributed to the effects of space weathering on the observed surface composition. The analysis by Binzel et al. (Binzel, R.P., Rivkin, A.S., Stuart, J.S., Harris, A.W., Bus, S.J., Burbine, T.H. 2004]. Icarus 170, 259–294) provided a missing link between the Q- and S-type bodies in near-Earth space by showing a reddening of spectral slope in objects from 0.1 to 5 km that corresponded to a transition from Q-type to S-type asteroid spectra, implying that size, and therefore surface age, is related to the relationship between S- and Q-types. The existence of Q-type asteroids in the main-belt was not confirmed until Mothé-Diniz and Nesvorny (Mothé-Diniz, T., Nesvorny, D. 2008]. Astron. Astrophys. 486, L9–L12) found them in young S-type clusters. The young age of these families suggest that the unweathered surface could date to the formation of the family. This leads to the question of whether older S-type main-belt families can contain Q-type objects and display evidence of a transition from Q- to S-type. To answer this question we have carried out a photometric survey of the Koronis family using the Kitt Peak 2.1 m telescope. This provides a unique opportunity to compare the effects of the space weathering process on potentially ordinary chondrite-like bodies within a population of identical initial conditions. We find a trend in spectral slope for objects 1–5 km that shows the transition from Q- to S-type in the main-belt. This data set will prove crucial to our understanding of the space weathering process and its relevant timescales. |
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