Using the youngest asteroid clusters to constrain the Space Weathering and Gardening rate on S-complex asteroids - Astrophysics > Earth and Planetary AstrophysicsReport as inadecuate




Using the youngest asteroid clusters to constrain the Space Weathering and Gardening rate on S-complex asteroids - Astrophysics > Earth and Planetary Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: 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.



Author: Mark Willman, Robert Jedicke, Nicholas Moskovitz, David Nesvorný, David Vokrouhlický, Thais Mothé-Diniz

Source: https://arxiv.org/







Related documents