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A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2


The peculiar object P/2010 A2 was discovered1 in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized2 class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010 A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results3. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009.

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Figure 1: Images of P/2010 A2 at four epochs.
Figure 2: Flux profiles along the trail.


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We thank R. Schulz and the Rosetta operations team for enabling these ‘target of opportunity’ observations to be performed. OSIRIS is funded by the national space agencies ASI, CNES, DLR, the Spanish Space Program (Ministerio de Educacion y Ciencia), SNSB and the ESA. The ground-based observations were collected (in part) at the European Southern Observatory, Chile, under programmes 084.C-0594(A) and 185.C-1033(A).

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Authors and Affiliations




C.S. and C.T. led this project and performed the data reduction and analysis, J.-B.V. did the modelling and led the interpretation, H.S., S.H. and R.M. were responsible for the planning and execution of the OSIRIS observations, H.B. contributed to the modelling and interpretation. C.B., D.K., P.L., H.R. and R.R. are the Lead Scientists of the OSIRIS project. The OSIRIS team built and run this instrument and made the observations possible. B.C., S.C.L., R.J.M.L., P.R.W. and A.F. were the observers who provided the ground-based observations. S.M. provided calculations of the collision probability.

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Correspondence to Colin Snodgrass.

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The authors declare no competing financial interests.

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Supplementary Information

This file contains Supplementary Material (observation details), additional references, Supplementary Table 1 and Supplementary Figures 1-6 with legends. (PDF 339 kb)

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Snodgrass, C., Tubiana, C., Vincent, JB. et al. A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2. Nature 467, 814–816 (2010).

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