The main belt 3628 Boznemcova asteroid as possible source of the LL6-chondrites

Abstract

The content of cosmogenic radionuclides, in particular, ^60Co and ^26Al, as well as VH-nucleus track density in the fresh-fallen Kilabo LL6-chondrite are measured. The obtained results and the available data of [5] on the content of ^26Al and noble gases in the fresh-fallen Bensour LL6-chondrite are used with earlier developed methods for determination of the pre-atmospheric sizes and orbits of these chondrites. The closeness of orbits of the Kilabo and Bensour chondrites, the striking likeness of their composition, structure and petrography allow us to suppose their origin from a single source; at the same time the resemblance of the reflection spectra of the LL6-chondrites with that of the main belt 3628 Boznemcova asteroid allow us to consider it as the parent body of the LL6-chondrites. On the strength of all the evidence, the following scenario is suggested: (1) knocking out of both the chondrites from the 3628 Boznemcova asteroid at a distance ∼2.2 AU from the Sun about 19 million years ago, the Bensour chondrite being knocked out from deeper layers of the parent asteroid, which were completely shielded from cosmic rays, while the material of the Kilabo chondrite being probably irradiated by cosmic rays on the asteroid surface for 14 million years before its knock-out; (2) the drift of the chondrites due to the Yarkovsky effect into the region of secular resonance g=g_6, which was accompanied by variation of the semimajor axis a by ∼0.05 AU over ∼18 million years; (3) the resonance transfer of the Kilabo and Bensour chondrites to their present orbits over the last ∼1 million years.

Keywords

• chondrites
• Kilabo
• Bensour
• asteroid 3628 Boznemcova
• Yarkovsky effect