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

Abstract

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 color 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 color 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 color measurement allows us to set an upper limit of ~64% on the disturbed surface portion. Using pre-existing color 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 color 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.

47 pages, 7 figures, 4 tables

References in corpus (8)

• The Seventh Data Release of the Sloan Digital Sky Survey
• K-corrections and filter transformations in the ultraviolet, optical, and near infrared
• Solar System Objects Observed in the SDSS Commissioning Data
• ESI, a new Keck Observatory echellette spectrograph and imager
• The Size Distributions of Asteroid Families in the SDSS Moving Object Catalog 4
• Redetermination of the space weathering rate using spectra of Iannini asteroid family members
• Collisions, Cosmic Radiation and the Colors of the Trojan Asteroids
• Rotation-Resolved Spectroscopy of a Very Young Asteroid, (1270) Datura

Cited by in corpus (17)

• Spectral properties of near-Earth and Mars-crossing asteroids using Sloan photometry
• Observations of "Fresh" and Weathered Surfaces on Asteroid Pairs and Their Implications on the Rotational-Fission Mechanism
• Collisional family structure within the Nysa-Polana complex
• Space Weathering Trends Among Carbonaceous Asteroids
• Asteroid Family Physical Properties
• Discovery of a young asteroid cluster associated with P/2012~F5 (Gibbs)
• Colors of Dynamically Associated Asteroid Pairs
• A common origin for dynamically associated near-Earth asteroid pairs
• I. Collisional evolution and reddening of asteroid surfaces: The problem of conflicting timescales and the role of size-dependent effects
• Rotationally Resolved Spectroscopy of Asteroid Pairs: No Spectral Variation Suggests Fission is followed by Settling of Dust
• Observational Constraints on the Catastrophic Disruption Rate of Small Main Belt Asteroids
• Spectral Similarity of Unbound Asteroid Pairs
• A Search for Subkilometer-sized Ordinary Chondrite Like Asteroids in the Main-Belt
• ASIME 2016 White Paper: In-Space Utilisation of Asteroids: "Answers to Questions from the Asteroid Miners"
• Lightcurves of the Karin family asteroids
• Recent formation and likely cometary activity of near-Earth asteroid pair 2019 PR2 -- 2019 QR6
• Space weathering of asteroids