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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.04.014 Byline: Pierre Vernazza (a), Alessandro Rossi (b), Mirel Birlan (c), Marcello Fulchignoni (a), Alin Nedelcu (c)(d), Elisabetta Dotto (e) Keywords: Asteroids; rotation; Spectroscopy; Asteroids; surfaces; Regoliths Abstract: 832 Karin is the largest member of the young Karin cluster that formed 5.75[+ or -]0.05Myr ago in the outer main belt. Surprisingly, recent near-IR spectroscopy measurements [Sasaki, T., Sasaki, S., Watanabe, J., Sekiguchi, T., Yoshida, F., Kawakita, H., Fuse, T., Takato, N., Dermawan, B., Ito, T., 2004. Astrophys. J. 615 (2), L161-L164] revealed that Karin's surface shows different colors as a function of rotational phase. It was interpreted that 832 Karin shows us the reddish space-weathered exterior surface of the parent body as well as an interior face, which has not had time to become space-weathered. This result is at odds with recent results including seismic and geomorphic modeling, modeling of the Karin cluster formation and measurements of the space weathering rate. Consequently, we aimed to confirm/infirm this surprising result by sampling Karin's spectrum well throughout its rotation. Here, we present new visible (0.45-0.95 [mu]m) and near-infrared (0.7-2.5 [mu]m) spectroscopic observations of 832 Karin obtained in January and April 2006, covering most of Karin's longitudes. In the visible range, we find that Karin shows no rotational spectral variations. Similarly, we find that Karin exhibits very little (to none) spectral variations with rotation in the near-IR range. Our results imply that 832 Karin has a homogeneous surface, in terms of composition and surface age. Our results also imply that the impact that generated the family refreshed entirely Karin's surface, and probably the surfaces of all members. Author Affiliation: (a) LESIA, Observatoire de Paris, 5 Place Jules Janssen, 92195 Meudon Principal Cedex, France (b) Spaceflight Dynamics Section, ISTI-CNR, Via Moruzzi 1, 56124 Pisa, Italy (c) IMCCE, Observatoire de Paris, 77 Av. Denfert Rochereau, 75014 Paris Cedex, France (d) Astronomical Institute of the Romanian Academy, Cutitul de Argint-5, Bucharest, Romania (e) INAF, Osservatorio Astronomico di Roma, Via Frascatti 33, 00040 Monteporzio Catone, Italy Article History: Received 6 December 2006; Revised 11 April 2007

We define a new approach to model asteroidal space weathering. We started from recent results of ion irradiation experiments (60-400 keV) of meteorites and silicates to give an accurate description of space weathering, and we included its effects in the Shkuratov model. We found that the reddening and darkening process (in the range 0.3-2.5 [micro]m) does not significantly affect the position or relative intensities of the mafic silicate absorption features and it mainly affects the continuum of reflectance spectra. This continuum is parameterized by a [C.sub.S] coefficient, which is strongly related with the number of displacements per unit area (damage parameter); we consequently obtained an exposure time curve, and corresponding astrophysical timescales. We applied this new description of space weathering to model observed spectra of Asteroid 832 Karin, in the 0.4-2.4 [micro]m spectral region. The obtained exposure time is slightly lower than the age of the impact and collisional breakup which originated the Karin asteroidal family, i.e., about 5.75 x [10.sup.6] years. Keywords: Asteroid, surfaces; Spectroscopy; Experimental techniques; Meteorites

A study shows that the rotational lightcurve of Apollo asteroid 4179 Toutatis is not periodic and has a large amplitude of about 1.2 magnitudes. This could be due to complex and tumbling rotation of the asteroid, with a characteristic period of three to seven days. The study is done using data collected from asteroid observation in Dec 1992, when it passed within 0.0242 AU of Earth.

In this short note the differences induced in the taxonomy obtained with the G-mode analysis by the corrected values of the IRAS albedo are presented. The results reveal the consistence of the nine main taxonomic classes.