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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.12.010 Byline: P. Vernazza (a), F. DeMeo (b), D.A. Nedelcu (c)(d), M. Birlan (d), A. Doressoundiram (b), S. Erard (b), E. Volquardsen (e) Keywords: Mercury, Surface Abstract: We present resolved near-infrared spectra of Mercury scanning 70% of the surface in latitude and longitude from three separate observations, allowing us to perform a compositional investigation of its surface. By scanning the surface we find that all spectra in our sample are remarkably similar suggesting overall compositional homogeneity. We do, however, observe a slope difference between the spectra. These slope changes are most likely due to differences in the emission angle over different parts of the surface. We confirm the presence of a 1.1[mu]m feature that had been previously detected (Warell, J. et al. [2006]. Icarus 180, 281-291) and attributed to Ca-rich clinopyroxene. Finally, we investigated Mercury's surface composition by comparing its spectrum with ground-based lunar spectra, lunar soil spectra collected in the laboratory, and analysis with a simple linear mixing model using various minerals as end-members. The result of this compositional investigation reveals that Mercury's surface composition is likely to be quite different from the Moon's. While low-Ca iron-rich pyroxenes are main surface components on the Moon (abundance varying from [approximately equal to]5% to [approximately equal to]35%), their abundance on Mercury may not exceed 5%. We also find that a Ca-rich clinopyroxene (in the hedenbergite-diopside series) is likely to be a main component of Mercury's surface whereas this mineral is almost absent on the Moon. Our analysis also suggests the possible presence of olivine. We find that Mercury's slope is less red than that of the Moon, in agreement with results from MESSENGER (McClintock, W.E., and 12 colleagues [2008]. Science 321, 62-65), and composition rather than variation of space weathering is likely the cause of this difference. Author Affiliation: (a) Research and Scientific Support Department, European Space Agency, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands (b) Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris, 5 Place Jules Janssen, Meudon F-92195, France (c) Astronomical Institute of the Romanian Academy, Str. Cutitul de Argint 5, Bucharest 040557, Romania (d) IMCCE, Observatoire de Paris, 77 Av. Denfert Rochereau, 75014 Paris Cedex, France (e) Institute for Astronomy, University of Hawaii, 640 N Aohoku Place, Hilo, HI 96720, USA Article History: Received 29 May 2009; Revised 4 December 2009; Accepted 4 December 2009

Abstract: We report follow-up observations of 477 program Near-Earth Asteroids (NEAs) using nine telescopes of the EURONEAR network having apertures between 0.3 and 4.2m. Adding these NEAs to our previous results we now count 739 program NEAs followed-up by the EURONEAR network since 2006. The targets were selected using EURONEAR planning tools focusing on high priority objects. Analyzing the resulting orbital improvements suggests astrometric follow-up is most important days to weeks after discovery, with recovery at a new opposition also valuable. Additionally we observed 40 survey fields spanning three nights covering 11 square degrees near opposition, using the Wide Field Camera on the 2.5m Isaac Newton Telescope (INT), resulting in 104 discovered main belt asteroids (MBAs) and another 626 unknown one-night objects. These fields, plus program NEA fields from the INT and from the wide field MOSAIC II camera on the Blanco 4m telescope, generated around 12000 observations of 2000 minor planets (mostly MBAs) observed in 34 square degrees. We identify Near Earth Object (NEO) candidates among the unknown (single night) objects using three selection criteria. Testing these criteria on the (known) program NEAs shows that the best selection method is our model which checks solar elongation and sky motion and the MPC's NEO rating tool. Our new data show that on average 0.5 NEO candidates per square degree should be observable in a 2m-class survey (in agreement with past results), while an average of 2.7 NEO candidates per square degree should be observable in a 4m-class survey (although our Blanco statistics were affected by clouds). At opposition just over 100 MBAs (1.6 unknown to every 1 known) per square degree are detectable to R=22 in a 2m survey based on the INT data (in accordance with other results), while our two best ecliptic Blanco fields away from opposition lead to 135 MBAs (2 unknown to every 1 known) to R=23. [Copyright &y& Elsevier]

Abstract: We report on the follow-up and recovery of 100 program NEAs, PHAs and VIs using the ESO/MPG 2.2m, Swope 1m and INT 2.5m telescopes equipped with large field cameras. The 127 fields observed during 11 nights covered 29 square degrees. Using these data, we present the incidental survey work which includes 558 known MBAs and 628 unknown moving objects mostly consistent with MBAs from which 58 objects became official discoveries. We planned the runs using six criteria and four servers which focus mostly on faint and poorly observed objects in need of confirmation, follow-up and recovery. We followed 62 faint NEAs within one month after discovery and we recovered 10 faint NEAs having big uncertainties at their second or later opposition. Using the INT we eliminated four PHA candidates and VIs. We observed in total 1286 moving objects and we reported more than 10,000 positions. All data were reduced by the members of our network in a team effort, and reported promptly to the MPC. The positions of the program NEAs were published in 27 MPC and MPEC references and used to improve their orbits. The O−C residuals for known MBAs and program NEAs are smallest for the ESO/MPG and Swope and about four times larger for the INT whose field is more distorted. For the astrometric reduction, the UCAC-2 catalog is recommended instead of USNO-B1. The incidental survey allowed us to study statistics of the MBA and NEA populations observable today with 1–2m facilities. We calculate preliminary orbits for all unknown objects, classifying them as official discoveries, later identifications and unknown outstanding objects. The orbital elements a, e, i calculated by FIND_ORB software for the official discoveries and later identified objects are very similar with the published elements which take into account longer observational arcs; thus preliminary orbits were used in statistics for the whole unknown dataset. We present a basic model which can be used to distinguish between MBAs and potential NEAs in any sky survey. Based on three evaluation methods, most of our unknown objects are consistent with MBAs, while up to 16 unknown objects could represent NEO candidates and four represent our best NEO candidates. We assessed the observability of the unknown MBA and NEA populations using 1 and 2m surveys. Employing a 1m facility, one can observe today fewer unknown objects than known MBAs and very few new NEOs. Using a 2m facility, a slightly larger number of unknown than known asteroids could be detected in the main belt. Between 0.1 and 0.8 new NEO candidates per square degree could be discovered using a 2m telescope. [Copyright &y& Elsevier]

Abstract: The European Near Earth Asteroid Research (EURONEAR) is a project which envisions to build a coordinated network which will follow-up and recover potentially hazardous asteroids (PHAs) and near earth asteroids (NEAs). We aim to include in EURONEAR two automated 1m telescopes located in Chile and Europe, in addition to other non-permanent facilities. Astrometry will be the main aim of the project in order to secure and follow-up newly discovered NEAs, also to recover PHAs at their second or following oppositions, while photometry of bright PHAs will bring information on their physical properties. In this paper, first we review briefly the existent and past NEAs programs. Next, we include the results obtained in 2006 from three observing runs at Pic du Midi using the 1m telescope, Haute-Provence employing the 1.2m telescope, and Bucharest using a small 23cm telescope. These add a total of 153 positions for 16 PHAs and NEAs, which were accepted by Minor Planet Center. Recently, a 1m telescope was allocated by ESO in La Silla to be automated and used as the Southern dedicated facility by EURONEAR. [Copyright &y& Elsevier]

Abstract: All available data regarding compositionally diagnostic measurements of asteroid (21) Lutetia are assembled. We review ground-based observations together with recent spacecraft mission (Rosetta, Herschel and Spitzer) measurements. The aim of this paper is to gather all the pieces of the Lutetia puzzle, in order to derive the most probable surface composition interpretation. During the flyby Rosetta observed only the northern hemisphere where OSIRIS imaging system found albedo variations of up to 30%. From our analyses of all the available data, taken at different aspect angles, variations on Lutetia''s surface are inferred to be due to compositional and morphological differences (at macro and micro scales). We conclude that Lutetia has a chondritic surface, possibly composed of mixtures of “incompatible” types of materials: carbonaceous and enstatite chondrites. Finding these materials juxtaposed could be the consequence of large impacts that created the present surface. [Copyright &y& Elsevier]

Abstract: In 2007, the asteroid Kalliope will reach one of its annual equinoxes. As a consequence, its small satellite Linus orbiting in the equatorial plane will undergo a season of mutual eclipses and occultations very similar to the one that the Galilean satellites undergo every 6 years. This paper is aimed at preparing a campaign of observations of these mutual events occurring from February to May 2007. This opportunity occurs only under favorable geometric conditions when the Sun and/or the Earth are close to the orbital plane of the system. This is the first international campaign devoted to the observation of photometric events within an asynchronous asteroidal binary system. We took advantage of a reliable orbit solution of Linus to predict a series of 24 mutual eclipses and 12 mutual occultations observable in the spring of 2007. Thanks to the brightness of Kalliope (), these observations are easy to perform even with a small telescope. Anomalous attenuation events could be observed lasting for about 1–3h with amplitude up to 0.09 mag. The attenuations are of two distinct types that can clearly be identified as primary and secondary eclipses similar to those that have been previously observed in other minor planet binary systems [Pravec, P., Scheirich, P., Kusnirák, P., Sarounová, L., Mottola, S., Hahn, G., Brown, P., Esquerdo, G., Kaiser, N., Krzeminski, Z., Pray, D.P., Warner, B.D., Harris, A.W., Nolan, M.C., Howell, E.S., Benner, L.A.M., Margot, J.-L., Galád, A., Holliday, W., Hicks, M.D., Krugly, Yu.N., Tholen, D., Whiteley, R., Marchis, F., Degraff, D.R., Grauer, A., Larson, S., Velichko, F.P., Cooney, W.R., Stephens, R., Zhu, J., Kirsch, K., Dyvig, R., Snyder, L., Reddy, V., Moore, S., Gajdos, S., Világi, J., Masi, G., Higgins, D., Funkhouser, G., Knight, B., Slivan, S., Behrend, R., Grenon, M., Burki, G., Roy, R., Demeautis, C., Matter, D., Waelchli, N., Revaz, Y., Klotz, A., Rieugné, M., Thierry, P., Cotrez, V., Brunetto, L., Kober, G., 2006. Photometric survey of binary near-Earth asteroids. Icarus 181, 63–93]. With these favorable circumstances, such photometric observations will provide us tight constraints regarding physical properties of Linus such as the size, shape and synodic spin period. [Copyright &y& Elsevier]

Abstract: We present an investigation of the lower atmosphere in the 25–40km altitude range from data of Venus’ night side in the 2.3- region. We used observations recorded at the NASA/IRTF in August 2004 with the SpeX spectro-imager. The previous conclusions of Marcq et al. [2005, Latitudinal variations of CO and OCS in the lower atmosphere of Venus from near-infrared nightside spectro-imaging, Icarus 179, 375–386] about CO and OCS abundance latitudinal variations are confirmed with a better accounting for cloud opacity variations; in particular, an enhancement of in CO at 36km is found at S with respect to the equator. There is also a depletion of OCS southward of S, that may be correlated with the CO increase. Information on the vertical gradients of the CO and OCS profiles was derived, yielding the following mixing ratios in the probed altitude range: . The study was also extended to and no latitudinal variations are found beyond our error bars ( at ). [Copyright &y& Elsevier]