Other
Scientific paper
Sep 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009dps....41.5302m&link_type=abstract
American Astronomical Society, DPS meeting #41, #53.02
Other
Scientific paper
During some time the OC paradox was considered a troublesome question for asteroid science.It is widely accepted now that its resolution lies in space weathering(SW) effects,that can morph the OC spectra into the typical spectra of S-class asteroids,that dominate the inner belt. Thus,a fraction of S-type asteroids would have OC-like composition.This fraction is still uncertain,ranging from 25% to >70%.The effectiveness of SW effects however creates a problem:the time scales for spectral alteration derived from lab experiments tend to be much shorter than the collisional lifetimes of asteroids.Although this fits well with the apparent abscence of asteroids with OC-like spectra in the Main Belt(MB),it seems at odds with the relatively high (30%)proportion of NEAs with OC-like spectra.This prompted Marchi et al.(2007) to propose a scenarium where the refreshment of the surfaces of NEAS is caused by tide effects due to close encounters with terrestrial planets, with times scales shorter than the collisional life of NEAs.If this tidal effect is indeed real, one should expect that the proportion of asteroids with OC-like spectra in the MB would be much smaller than what is found among NEAs.To this end we seached for MB asteroids with vis-spectra similar to OC-meteorites using data from SMASSII and S3OS2 surveys,added to observations with Gemini telescope,to probe at smaller MB asteroids.Surprisingly we found that a large number of MB asteroids have spectra that match well the spectra of OC meteorites.Also,the fraction of of OC-like asteroids among the asteroids >5 km diameter the MB is undistinghishable from what is seen among NEAS in the same size range.Therefore,there is no shortage of MB asteroids with OC-like spectra, and since tidal effects are not an issue for MB asteroids,some other mechanism must be invoked to explain the abundance of asteroids with apparent unweathered surfaces both in the MB and among NEAs.
Carvano Jorge M.
Jasmin F. L.
Lazzaro Daniela
Mothé-Diniz Thais
Nesvorný David
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