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We have extended our earlier work on space weathering of the youngestS-complex asteroid families to include results from asteroid clusters with ages<10^6 years and to newly identified asteroid pairs with ages <5x10^5 years. Wehave identified three S-complex asteroid clusters with ages in the range10^{5-6} years. The average color of the objects in these clusters agree withthe prediction of Willman et al., 2008. SDSS photometry of the members of veryyoung asteroid pairs with ages <10^5 years was used to determine theirtaxonomy. The average color of the S-complex pairs is PC_1=0.49+/-0.03, over5-sigma redder than predicted by Willman et al., 2008. Therefore, the mostlikely pair formation mechanism is gentle separation due to YORP spin-upleaving much of the aged and reddened surface undisturbed. In this case ourcolor measurement allows us to set an upper limit of ~64% on the disturbedsurface portion. Using pre-existing color data and our new results for theyoungest S-complex asteroid clusters we have extended our space weather modelto explicitly include the effects of regolith gardening and fit separateweathering and gardening characteristic timescales of tau_w=960+/-160My andtau_g=2000+/-290My respectively. The first principal component color for freshS-complex material is 0.37+/-0.01 while the maximum amount of local reddeningis 0.33+/-0.06. Our first-ever determination of the gardening time is in starkcontrast to our calculated gardening time of tau_g~270My based on main beltimpact rates and reasonable assumptions about crater and ejecta blanket sizes.A possible resolution for the discrepancy is through a `honeycomb' mechanism inwhich the surface regolith structure absorbs small impactors without producingsignificant ejecta. This mechanism could also account for the paucity of smallcraters on (433) Eros.

Using the youngest asteroid clusters to constrain the Space Weathering and Gardening rate on S-complex asteroids