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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.02.015 Byline: S. Fornasier (a)(b), A. Migliorini (c), E. Dotto (d), M.A. Barucci (a) Keywords: Asteroids; surface; Spectroscopy Abstract: We present the results of a visible spectroscopic survey of igneous asteroids belonging to the small and intriguing E-class, including 2867 Steins, a target of the Rosetta mission. The survey was carried out at the 3.5 m Telescopio Nazionale Galileo (TNG), and at the 3.5 m New Technology Telescope (NTT) of the European Southern Observatory. We obtained new visible spectra for eighteen E-type asteroids, and near infrared spectra for eight of them. We confirm the presence of three different mineralogies in the small E-type populations. We classify each object in the E[I], E[II] or E[III] subgroups [Gaffey, M.J., Kelley, M.S., 2004. Lunar Planet. Sci. XXXV. Abstract 1812] on the basis of the spectral behavior and of the eventual presence of absorption features attributed to sulfides (such the 0.49 [mu]m band, on E[II]), or to iron bearing silicates (0.9 [mu]m band, on E[III]). We suggest that some asteroids (i.e. 64 Angelina, 317 Roxane, and 434 Hungaria), which show different spectral behavior comparing our data with those available in literature, have an inhomogeneous surface composition. 2867 Steins, a target of the Rosetta mission, shows a spectral behavior typical of the E[II] subgroup, as already suggested by Barucci et al. [Barucci, M.A., Fulchignoni, M., Fornasier, S., Dotto, E., Vernazza, P., Birlan, M., Binzel, R.P., Carvano, J., Merlin, F., Barbieri, C., Belskaya, I., 2005. Astron. Astrophys. 430, 313-317] and Fornasier et al. [Fornasier, S., Marzari, F., Dotto, E., Barucci, M.A., Migliorini, A., 2007. Astron. Astrophys. 474, 29-32]. Litva and 1990 TN1, initially classified as E-types, show a visible and near infrared behavior consistent with the olivine rich A-class asteroids, while 5806 Archieroy, also supposed to belong to the E-class, has a spectral behavior consistent with the S(V) classification following the Gaffey et al. [Gaffey, M.J., Burbine, T.H., Piatek, J.L., Reed, K.L., Chaky, D.A., Bell, J.F., Brown, R.H., 1993. Icarus 106, 573-602] classification scheme. To fully investigate the E-type population, we enlarged our sample including 6 E-type asteroids spectra available in literature, resulting in a total sample of 21 objects. The analysis of the spectral slope for the 3 different E-type subgroups versus the orbital elements show that E[III] members have the lowest mean spectral slope value inside the whole sample, and that they are located between 2.2-2.7 AU in low inclination orbits. E[II] members has the highest spectral slope inside the sample, half of them are located in the Hungaria region, 2 are NEA and 2 (64 Angelina and 2867 Steins), are in the main belt. A similar distribution is found for the 5 featureless E[I] members, located mainly in the Hungaria region (3 members), one in the middle main belt while one is a NEA (2004 VD17). Finally, for the five E-type asteroids observed both in the visible and near infrared range, plus 2867 Steins, we attempt to model their surface composition using linear geographical mixtures of no more than 3 components, selected from aubrite meteorites and correlated minerals. In particular we suggest that the aubrite PeA[+ or -]a Blanca might have the E[III] Asteroid 317 Roxane as parent body, and that the aubrite ALH78113 might be related to the E[II] subgroup asteroids. Author Affiliation: (a) LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92195 Meudon Principal Cedex, France (b) Universite de Paris 7 Denis Diderot, 4, rue Elsa Morante, 75205 Paris Cedex 13, France (c) IASF-INAF, via del Fosso del Cavaliere 100, 00133 Roma, Italy (d) INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone, Roma, Italy Article History: Received 10 October 2007; Revised 26 February 2008 Article Note: (footnote) [star] Based on observations carried out at the European Southern Observatory (ESO), La Silla, Chile, ESO proposals 074.C-0049 and 078.C-0115 and at the Telescopio Nazionale Galileo.

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

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.03.033 Byline: S. Fornasier (a)(b), E. Dotto (c), O. Hainaut (d), F. Marzari (e), H. Boehnhardt (f), F. De Luise (c), M.A. Barucci (b) Keywords: Trojan asteroids; Asteroids; composition; Photometry; Spectroscopy Abstract: We present the results of a visible spectroscopic and photometric survey of Jupiter Trojans belonging to different dynamical families. The survey was carried out at the 3.5 m New Technology Telescope (NTT) of the European Southern Observatory (La Silla, Chile) in April 2003, May 2004 and January 2005. We obtained data on 47 objects, 23 belonging to the L5 swarm and 24 to the L4 one. These data together with those already published by Fornasier et al. [Fornasier, S., Dotto, E., Marzari, F., Barucci, M.A., Boehnhardt, H., Hainaut, O., de Bergh, C., 2004a. Icarus 172, 221-232] and Dotto et al. [Dotto, E., Fornasier, S., Barucci, M.A., Licandro, J., Boehnhardt, H., Hainaut, O., Marzari, F., de Bergh, C., De Luise, F., 2006. Icarus 183, 420-434], acquired since November 2002, constitute a total sample of visible spectra for 80 objects. The survey allows us to investigate six families (Aneas, Anchises, Misenus, Phereclos, Sarpedon, Panthoos) in the L5 cloud and four L4 families (Eurybates, Menelaus, 1986 WD and 1986 TS6). The sample that we measured is dominated by D-type asteroids, with the exception of the Eurybates family in the L4 swarm, where there is a dominance of C- and P-type asteroids. All the spectra that we obtained are featureless with the exception of some Eurybates members, where a drop-off of the reflectance is detected shortward of 5200 A. Similar features are seen in main belt C-type asteroids and commonly attributed to the intervalence charge transfer transition in oxidized iron. Our sample comprises fainter and smaller Trojans as compared to the literature's data and allows us to investigate the properties of objects with estimated diameter smaller than 40-50 km. The analysis of the spectral slopes and colors versus the estimated diameters shows that the blue and red objects have indistinguishable size distribution, so any relationship between size and spectral slopes has been found. To fully investigate the Trojans population, we include in our analysis 62 spectra of Trojans available in literature, resulting in a total sample of 142 objects. Although the mean spectral behavior of L4 and L5 Trojans is indistinguishable within the uncertainties, we find that the L4 population is more heterogeneous and that it has a higher abundance of bluish objects as compared to the L5 swarm. Finally, we perform a statistical investigation of the Trojans's spectra property distributions as a function of their orbital and physical parameters, and in comparison with other classes of minor bodies in the outer Solar System. Trojans at lower inclination appear significantly bluer than those at higher inclination, but this effect is strongly driven by the Eurybates family. The mean colors of the Trojans are similar to those of short period comets and neutral Centaurs, but their color distributions are different. Author Affiliation: (a) University of Paris 7 'Denis Diderot,' 10 rue Alice Domon et Leonie Duquet, 75013 Paris, France (b) LESIA, Paris Observatory, Batiment 17, 5 Place Jules Janssen, 92195 Meudon Cedex, France (c) INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monteporzio Catone (Roma), Italy (d) European Southern Observatory, Casilla 19001, Santiago, Chile (e) Dipartimento di Fisica, Universita di Padova, Via Marzolo 8, 35131 Padova, Italy (f) Max-Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany Article History: Received 2 December 2006; Revised 20 March 2007 Article Note: (footnote) [star] Based on observations carried out at the European Southern Observatory (ESO), La Silla, Chile, ESO proposals 71.C-0650, 73.C-0622, 74.C-0577.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.02.012 Byline: E. Dotto (a), S. Fornasier (b), M.A. Barucci (c), J. Licandro (d)(e), H. Boehnhardt (f), O. Hainaut (g), F. Marzari (h), C. de Bergh (c), F. De Luise (a) Keywords: Asteroids; Photometry; Spectroscopy Abstract: Asteroid dynamical families are supposed to be formed from the collisional disruption of parent bodies. As a consequence, the investigation of the surface properties of small and large family members may give some hints on the nature of the dynamical group, the internal composition of the parent body, and the role played by space weathering processes in modifying the spectral behavior of the members' surfaces. In this work we present visible-near-infrared observations of 24 Jupiter Trojans belonging to seven dynamical families of both the L4 and L5 swarms. The most important characteristics we found is the uniformity of the Trojans population. All the investigated Trojans have featureless spectra and a spectral behavior typical of the primitive P and D taxonomic classes. In particular, no signatures of water ice have been found on the spectra of these primordial bodies. From our investigation, the L4 and L5 clouds appear to be compositionally indistinguishable. Tentative models of the surface composition, based on the Hapke theory, are presented and discussed. Author Affiliation: (a) INAF, Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone (Roma), Italy (b) Department of Astronomy, University of Padova, Vicolo dell'Osservatorio 2, I-35122 Padova, Italy (c) LESIA, Observatoire de Paris-Meudon, 5 Place Jules Janssen, 92195 Meudon, France (d) Isaac Newton Group of Telescopes, P.O. Box 321, E-38700 Santa Cruz de la Palma, Tenerife, Spain (e) Instituto de Astrofisica de Canarias, c/Via Lactea s/n, E-38200 La Laguna, Tenerife, Spain (f) Max Planck Institute for Solar System Research, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau, Germany (g) European Southern Observatory, Casilla 19001, Santiago, Chile (h) Department of Physics, University of Padova, Via Marzolo 8, I-35131 Padova, Italy Article History: Received 27 June 2005; Revised 14 February 2006 Article Note: (footnote) [star] Based on observations carried out at the European Southern Observatory (ESO), La Silla, Chile, ESO proposals 69.C-0524 and 71.C-0650, and at the Telescopio Nazionale Galileo, La Palma, Canary Island, proposals TAC06 (AOT7) and TAC705 (AOT6).

We present results obtained for Epinal (H5), an ordinary chondrite meteorite, irradiated with 60 keV [Ar.sup.++] ions, simulating solar wind heavy particle irradiation. Bidirectional reflectance spectra (0.3-2.67 [micro]m) measured after irradiating Epinal samples with different ion fluences exhibit a progressive reddening that is similar to the spread of spectra observed for S-type near-Earth asteroids. The timescales for inducing the same effects in space as those obtained in laboratory are estimated to be [10.sup.4]-[10.sup.6] yr. These results suggest irradiation by heavy ions may be a very efficient weathering process in near-Earth space. Keywords: Meteorites; Spectroscopy; Experimental techniques; Radiation chemistry; Asteroid surfaces

In this paper we present results obtained in the framework of a visible spectroscopic and photometric survey of Trojan asteroids. We concentrated on bodies orbiting at the L5 Lagrangian point of Jupiter that are also members of dynamical families. Spectroscopy is a crucial tool that allows us to characterize the mineralogical composition of families and their parent bodies, gives evidence of ongoing space weathering, and confirms family membership. We have observed 18 objects belonging to the Aneas, Astyanax, Sarpedon, and Phereclos families as defined by Beauge and Roig (2001, Icarus 53, 391). In addition, we have determined the spectroscopic properties of 8 background Jupiter Trojans. The observed spectra are reddish with a dominance of D-type asteroids. As expected, the spectra of the non-family members are more heterogeneous compared to the spectra of family members, with the exception of the members of the Aneas family. We also confirm the lack of absorption features in the visible region, as already reported by other authors. Keywords: Asteroids; Photometry; Spectroscopy: Jupiter Trojans; Families

Most ion irradiation experiments relevant to primitive outer Solar System objects have been performed on ice and silicate targets. Here we present the first ion irradiation experiments performed on natural complex hydrocarbons (asphaltite and kerite). These materials are very dark in the visible and have red-sloped spectra in the visible and near-infrared. They may be comparable in composition and structure to refractory organic solids on the surfaces of primitive outer Solar System objects. We irradiated the samples with 15-400 keV H+, N+, Ar++, and He+ ions and measured their reflectance spectra in the range of 0.3-2.5 [micro]m before ion implantation and after each irradiation step. The results show that irradiation-induced carbonization gradually neutralizes the spectral slopes of these red organic solids. This implies a similar space weathering trend for the surfaces of airless bodies optically dominated by spectrally red organic components. The reduction of spectral slope was observed in all experiments. Irradiation with 30 keV protons, which transfers energy to the target mostly via electronic (inelastic) collisions, showed lower efficiency than the heavier ions. We found that spectral alteration in our experiments increased with increasing contribution of nuclear versus electronic energy loss. This implies that nuclear (elastic) energy deposition plays an important role in changing the optical properties of irradiated refractory complex hydrocarbon materials. Finally, our results indicated that temperature variations from 40 K to room temperature did not influence the spectral properties of these complex hydrocarbon solids. Keywords: Radiation chemistry; Organic chemistry; Spectroscopy

10199 Chariklo (1997 CU26) is the largest Centaur so far known. We carded out near-infrared observations of this object during two different runs separated by a year. Although no evidence for spectral variations has been found over short time scales slight differences have been detected between the two observational runs. We interpret these findings as likely due to a heterogeneous composition of the surface of Chariklo. We suggest two different models comprising geographical mixtures of tholins, amorphous carbon, and water ice in slightly different percentages. Our observations confirm the presence of water ice on the surface of this Centaur, as already detected by Brown et al. (1998, Science 280, 1430-1432) and Brown and Koresko (1998, Astrophys. J. 505, L65-67). Keywords: Centaurs; Spectroscopy; Near-infrared observations

Transneptunian objects and Centaurs are supposed to be among the most pristine bodies of the Solar System. To investigate their physical properties and their surface composition, an ESO large program at the Very Large Telescope was carried out. In this paper we present photometric and spectroscopic near-infrared data of two Centaurs (1998 SG35 and 2000 QC243) and one transneptunian object (47171 1999 TC36). For 47171 1999 TC36 and 1998 SG35 visible photometry is also presented. Models of the surface composition of these objects are presented and discussed. By including a small percentage of water ice in our geographical mixtures, we obtain a better agreement with the observations in the H and K bands. Keywords: Centaurs; Transneptunian objects; 2000 QC243; 1998 SG35; 47171 1999 TC36; Spectroscopy; Photometry; Visible; Near-infrared

Lightcurve observations of 16 near-Earth objects (NEOs) and 2 Mars-crossers in 1996-1999 from three observational sites are presented. Eight objects were observed shortly after their discovery within the follow-up program of NEO observations. We were able to determine rotation periods for 14 asteroids. For 8 objects (5626, 5732, 1998 FM5, 1998 FX2, 1998 UT18, 1998 VO33, 1999 RQ36, 1999 US3) our determinations constitute new results while in the remaining 6 cases (3200, 4341, 7025, 7822, 11066, 1992 QN) we could improve or confirm previously published periods. We also put constraints on the spin vector of 3200 Phaethon. Key Words: asteroids; rotation; photometry.

Observations of emissivity features of 10 Hygiea have been made for the first time in the relatively unexplored thermal-infrared wavelength region with the ISO (Infrared Space Observatory) satellite. Spectrophotomer (PHT-S) and short wavelength spectrometer (SWS) spectra of 10 Hygiea, obtained at 5.8-11.6 and 7-45 [micro]m, respectively, are presented. In order to remove the thermal emission continuum, an advanced thermo-physical model has been applied to the observational data. To better interpret the spectral features above the thermal emission continuum, we compared the ISO observations with laboratory spectra available in the literature. Several laboratory experiments on minerals and meteorites have been performed to complete the analysis and to study the spectral behavior at various grain sizes. A possible spectral similarity with CO carbonaceous chondrites at small grain size is demonstrated. Key Words: asteroids; 10 Hygiea; infrared observations; spectroscopy; ISO.

We observed 44 Eunomia family members at ESO (European Southern Observatory) and at CASLEO (Complejo Astronomico El Leoncito) in the wavelength range of 4900-9200 (angstroms). We found 41 objects with the same characteristics: a maximum around (lambda) = 7500 (angstroms), and a reflectivity gradient spanning a continuous but limited range. Only 3 objects display featureless spectra similar to C-type asteroids, and these should be considered as interlopers. The spectra of the 41 objects show a similarity which is consistent with the dynamical hypothesis of a common origin. On the other hand, the spread of distribution of surface composition also indicates that the Eunomia family was possibly formed from the fragmentation of a partially differentiated S-type parent body. Key Words: asteroids; asteroids, composition; spectroscopy; surfaces, asteroids.

We observed 47 Flora clan members at the ESO (European Southern Observatory) in the wavelength range 4900-9200 [Angstrom]. We found 42 objects with common characteristics: a maximum around [Lambda] = 7500 [Angstrom] and a reflectivity gradient spanning a continuous but limited range. Only five objects show different spectral behavior (one is probably V type). Looking for meteorite analogs, we only find four ordinary chondrites that present features similar to those of the lower part of the Flora spectral distribution. This behavior is consistent as the consequence of some space-weathering process.

This paper contains the statistics of close encounters of observed minor bodies with the Earth. Five classes of small objects have been examined, namely: near-Earth asteroids (Aten, Apollo, and Amor), short-period comets, and long-period comets. The motion of objects belonging to the first four classes has been integrated over a time span of 821.4 years, while the motion of long-period comets has been followed for 60 years, centered on the discovery epoch. The behavior in time of the minimum orbit intersection distance (MOID) is studied, and frequency curves of close passages according to the distance from Earth are provided and discussed.

We present the results of photometric observations of 12 asteroids, performed from 1985 through 1989 at the Astronomical Observatory of Teramo (Italy), Astronomical Observatory of Turin (Italy), and European Southern Observatory (ESO, La Silla, Chile). Using the EA pole determination method described in G. De Angelis (Planet. Space Sci., 41, 285-290, 1993), we have obtained the first spin and shape solution of 85 Io and 360 Carlova and an improvement of the previous determinations for 12 Victoria, 192 Nausikaa and 423 Diotima, for which we determined for the first time the sidereal period and the sense of rotation. We have checked the determinations obtained by other authors for the asteroids 3 Juno, 6 Hebe, 20 Massalia, 43 Ariadne, and 52 Europa, and suggested a very rough estimate of the spin and shape parameters of 115 Thyra.

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.

Photoelectric studies of 16 asteroids at Chile's European Southern Observatory with the 1-m telescope reveals that the 56 single-night light curves of the asteroids vary with the rotational period. Fourier analysis helps compute the synodic rotational period for 11 asteroids. The other five asteroids do not exhibit a complete rotational period. Rotational period values help evaluate reliability code, lightcurve amplitude and the diameters of color bands.

Data from the European Southern Observatory in Chile from 1984 to 1992 help determine rotational behavior of small asteroids and derive bias-free photoelectric observations of small asteroids. A computer program that includes the extinction difference between asteroid and comparison star helps reduce the data that determines complete light curves and reliable rotation periods for various asteroids.

Spin vector and shape of the asteroid 243 Ida were obtained from groundbased photometric observations of the asteroid over seven apparitions from 1980 to 1993. The solutions for the spin vector at ecliptic coordinates are also obtained. The required angles for the study of the low orbital inclination of Ida is restricted by the spin vector ambiguity. The rotation of the asteroid is retrograde and has a sidereal period of 4.6336 hours. The axial ratios are 1.82 and 1.15, as revealed by the ellipsoid model.

Photometric observations of asteroid 951 Gaspra taken prior tothe Galileo deep-space probe flyby were analyzed to determine the characteristics of the minor planet. The results showed that Gaspra had a solarphase angle dependence which exhibited a G value of around 0.29 for the lightcurve maxima. In combination with data obtained by the Galileo space probe, the information gathered from these images allowed a groundbased model of Gaspra to be formulated.