* Astronomy

Members Login
    Remember Me  
Post Info TOPIC: S-complex asteroids


Posts: 131433
S-complex asteroids

Title: Using the youngest asteroid clusters to constrain the Space Weathering and Gardening rate on S-complex asteroids
Authors: Mark Willman, Robert Jedicke, Nicholas Moskovitz, David Nesvorný, David Vokrouhlický, Thais Mothé-Diniz

We have extended our earlier work on space weathering of the youngest S-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. We have identified three S-complex asteroid clusters with ages in the range 10^{5-6} years. The average colour of the objects in these clusters agree with the prediction of Willman et al., 2008. SDSS photometry of the members of very young asteroid pairs with ages <10^5 years was used to determine their taxonomy. The average colour of the S-complex pairs is PC_1=0.49±0.03, over 5-sigma redder than predicted by Willman et al., 2008. Therefore, the most likely pair formation mechanism is gentle separation due to YORP spin-up leaving much of the aged and reddened surface undisturbed. In this case our colour measurement allows us to set an upper limit of ~64% on the disturbed surface portion. Using pre-existing colour data and our new results for the youngest S-complex asteroid clusters we have extended our space weather model to explicitly include the effects of regolith gardening and fit separate weathering and gardening characteristic timescales of tau_w=960±160My and tau_g=2000±290My respectively. The first principal component colour for fresh S-complex material is 0.37±0.01 while the maximum amount of local reddening is 0.33±0.06. Our first-ever determination of the gardening time is in stark contrast to our calculated gardening time of tau_g~270My based on main belt impact rates and reasonable assumptions about crater and ejecta blanket sizes. A possible resolution for the discrepancy is through a 'honeycomb' mechanism in which the surface regolith structure absorbs small impactors without producing significant ejecta. This mechanism could also account for the paucity of small craters on (433) Eros.

Read more (658kb, PDF)

Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.

Create your own FREE Forum
Report Abuse
Powered by ActiveBoard