Towards a general model of space weathering of S-complex asteroids and ordinary chondrites

¹ Dipartimento di Fisica, Università di Pisa, largo Pontecorvo 3, 56127 Pisa, Italy e-mail: paolicchi@df.unipi.it
² Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: simone.marchi@unipd.it
³ Department of Space Studies, Southwest Research Institute, 1050 Walnut St., Boulder, CO 80302, USA e-mail: davidn@boulder.swri.edu
⁴ Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: sara.magrin.1@unpid.it
⁵ Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: monica.lazzarin@unpid.it

Received: 10 October 2006
Accepted: 5 January 2007

Abstract

Context.The effect of the space weathering on the spectral properties of the S-complex asteroids has been widely discussed in recent times, and a systematic reddening due to the exposure to the various influxes has been found. The evolution of spectral properties is also affected by other processes, such as close encounters with planetary bodies.

Aims. In this paper we present our model of asteroidal space weathering, combining the previous analyses and using an increased dataset. We also provide a link with ordinary chondrite meteorites.

Methods. We revise also some age estimates in terms of dynamical and physical considerations.

Results. The present analysis qualitatively confirms the previous results, but a by far more refined and reliable slope-exposure relation is obtained, capable to include in a unique scenario the ordinary chondrite meteorites, NEOs, Mars Crossers and Main Belt asteroids. Moreover, we show that, on the basis of spectroscopic properties, Mars Crossers should be, on the average, significantly younger than Main Belt asteroids of the same size. Finally, we find that the solar ion flux is the most relevant source of the asteroidal space weathering.

Conclusions. The properties of ordinary chondrite meteorites, NEOs, Mars Crossers and Main Belt asteroids can be included in a unique scenario. This has unveiled the relevant processes – some newly discovered – which play an important role in determining the evolution of the spectral properties of these bodies over time.