Sunlight scattered by asteroidal surfaces is partially linearly polarized. The polarization depends on the physical properties of the particles (size, refractive index, structure), and varies with the geometry of observations (phase angle) and wavelength. The polarization phase curves of asteroids with a bell-shaped positive branch and a shallow negative branch are typical of irregular particles. The polarization maxima are observable only for near-Earth objects, while observations of main belt asteroids are limited to relatively small phase angles, mainly in the negative branch. The polarimetric phase curve parameters allow a classification into various types [1], which are similar to the spectral classification. They also provide information on, e.g. the bulk surface albedo by the slope at inversion and a two parameters empirical function [2]. Observations of NEA objects are expected in the near future to better characterize their surface properties [3]. The determination of the parent bodies of most classes of asteroids still remains a puzzling question. It is thus of interest to compare the properties of some meteorites to their potential progenitors. Powdered meteorites in different size distributions deposited on a surface are used as regolith analogues of their parent body. Such work is in progress with the PROGRA2 experiment (http://www.icare.univ-lille1.fr). First, we present the instrumental set-up for the laboratory work on surfaces and explain how we use also microgravity measurements on clouds of the particles to infer the size influence on the polarimetric phase curves. Second, we present some results for meteorites and finally we compare the phase curves parameters to the observational results of asteroids to tentatively infer some physical properties of the regoliths [4]. We acknowledge CNES and ESA support for the microgravity flights and experimental work References [1] A. Penttilä, K. Lumme, E. Hadamcik and A.C. Levasseur-Regourd. Statistical analysis of asteroidal and cometary polarization phase curves. A&A 432 (2005) [2] A. Cellino, R. Gil-Hutton, E.F. Tedesco, M. DiMartino and A. Brunini. Polarimetric observations of small asteroids: preliminary results. Icarus 138 (1999) [3] A.C. Levasseur-Regourd et al., Small bodies studied by polarimetry, to select appropriate targets for sample-return missions to primitive near-Earth asteroids. Submitted to MPAS (2012). [4] E. Hadamcik, A.C. Levasseur-Regourd, J.-B. Renard, J. Lasue, A.K. Sen. Polarimetric observations and laboratory simulations of asteroidal surfaces: the case of 21 Lutetia. JQSRT 112 (2011)
