M. Lazzarin

University of Padova, Padua, Veneto, Italy

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Publications (125)376.19 Total impact

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    ABSTRACT: Context. The ESA cometary mission Rosetta was launched in 2004. In the past years and until the spacecraft hibernation in June 2011, the two cameras of the OSIRIS imaging system (Narrow Angle and Wide Angle Camera, NAC and WAC) observed many di�erent sources. On 20 January 2014 the spacecraft successfully exited hibernation to start observing the primary scientific target of the mission, comet 67P/Churyumov-Gerasimenko. Aims. A study of the past performances of the cameras is now mandatory to be able to determine whether the system has been stable through the time and to derive, if necessary, additional analysis methods for the future precise calibration of the cometary data. Methods. The instrumental responses and filter passbands were used to estimate the e�ciency of the system. A comparison with acquired images of specific calibration stars was made, and a refined photometric calibration was computed, both for the absolute flux and for the reflectivity of small bodies of the solar system. Results. We found a stability of the instrumental performances within �1.5% from 2007 to 2010, with no evidence of an aging e�ect on the optics or detectors. The e�ciency of the instrumentation is found to be as expected in the visible range, but lower than expected in the UV and IR range. A photometric calibration implementation was discussed for the two cameras. Conclusions. The calibration derived from pre-hibernation phases of the mission will be checked as soon as possible after the awakening of OSIRIS and will be continuously monitored until the end of the mission in December 2015. A list of additional calibration sources has been determined that are to be observed during the forthcoming phases of the mission to ensure a better coverage across the wavelength range of the cameras and to study the possible dust contamination of the optics.
    Astronomy and Astrophysics 02/2015; 574:A123. · 4.48 Impact Factor
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    ABSTRACT: Images of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) imaging system onboard the European Space Agency's Rosetta spacecraft at scales of better than 0.8 meter per pixel show a wide variety of different structures and textures. The data show the importance of airfall, surface dust transport, mass wasting, and insolation weathering for cometary surface evolution, and they offer some support for subsurface fluidization models and mass loss through the ejection of large chunks of material. Copyright © 2015, American Association for the Advancement of Science.
    Science 01/2015; 347(6220):aaa0440. · 31.48 Impact Factor
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    ABSTRACT: Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency's Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10(-10) to 10(-7) kilograms, and 48 grains of mass 10(-5) to 10(-2) kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails. Copyright © 2015, American Association for the Advancement of Science.
    Science 01/2015; 347(6220):aaa3905. · 31.48 Impact Factor
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    ABSTRACT: Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss.
    Science 01/2015; 347(6620). · 31.48 Impact Factor
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    Astronomy and Astrophysics 01/2015; 573(A62). · 4.48 Impact Factor
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    ABSTRACT: Aims. Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P's nucleus. Methods. Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations. Results. Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P 1 = 12.76129 ± 0.00005 h and P 2 = 12.4043 ± 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates λ = 65 • ± 15 • , β = +59 • ± 15 • , corresponding to equatorial coordinates RA = 22 • , Dec = +76 • . However, we find that the mirror solution, also prograde, at λ = 275 • ± 15 • , β = +50 • ± 15 • (or RA = 274 • , Dec = +27 •), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane.
    Astronomy and Astrophysics 09/2014; 569(L2). · 4.48 Impact Factor
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    ABSTRACT: This work focuses on the study of the aqueous alteration process which acted in the main belt and produced hydrated minerals on the altered asteroids. The aqueous alteration is particularly important for unraveling the processes occurring during the earliest times of the Solar System history, as it can give information both on the asteroids thermal evolution and on the localization of water sources in the asteroid belt. We present new spectral observations in the visible region of 80 asteroids belonging to the primitive classes C, G, F, B and P. We combine the present observations with the visible spectra of asteroids available in the literature for a total of 600 primitive main belt asteroids. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and increases through the F, B, C, and G asteroids. Around 50% of the observed C-type asteroids show absorption features in the vis. range due to hydrated silicates, implying that more than 70% of them will have a 3 $\mu$m absorption band and thus hydrated minerals on their surfaces. The process dominates in primitive asteroids located between 2.3 and 3.1 AU, that is at smaller heliocentric distances than previously suggested. The aqueous alteration process dominates in the 50--240 km sized primitive asteroids, while it is less effective for bodies smaller than 50 km. No correlation is found between the aqueous alteration process and the asteroids albedo or orbital elements. Comparing the $\sim$ 0.7 $\mu$m band parameters of hydrated silicates and CM2 carbonaceous chondrites, we see that the band center of meteorites is at longer wavelengths than that of asteroids. This difference on center positions may be attributed to different minerals abundances, and to the fact that CM2 available on Earth might not be representative of the whole aqueous altered asteroids population.
    Icarus 02/2014; 233. · 2.84 Impact Factor
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    ABSTRACT: This paper describes the spectral modeling of the surface of Phobos in the wavelength range between 0.25 and 4.0 μm. We use complementary data to cover this spectral range: the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System on board the ESA Rosetta spacecraft) reflectance spectrum that Pajola et al. merged with the VSK-KRFM-ISM (Videospectrometric Camera (VSK)–Combined Radiometer and Photometer for Mars (KRFM)–Imaging Spectrometer for Mars (ISM) on board the USSR Phobos 2 spacecraft) spectra by Murchie & Erard and the IRTF (NASA Infrared Telescope Facility, Hawaii, USA) spectra published by Rivkin et al. The OSIRIS data allow the characterization of an area of Phobos covering from 86.8 N to 90 S in latitude and from 126◦ W to 286◦ W in longitude. This corresponds chiefly to the trailing hemisphere, but with a small sampling of the leading hemisphere as well. We compared the OSIRIS results with the Trojan D-type asteroid 624 Hektor and show that the overall slope and curvature of the two bodies over the common wavelength range are very similar. This favors Phobos being a captured D-type asteroid as previously suggested. We modeled the OSIRIS data using two models, the first one with a composition that includes organic carbonaceous material, serpentine, olivine, and basalt glass, and the second one consisting of Tagish Lake meteorite and magnesium-rich pyroxene glass. The results of these models were extended to longer wavelengths to compare the VSK-KRFM-ISM and IRTF data. The overall shape of the second model spectrum between 0.25 and 4.0 μm shows curvature and an albedo level that match both the OSIRIS and Murchie & Erard data and the Rivkin et al. data much better than the first model. The large interval fit is encouraging and adds weight to this model, making it our most promising fit for Phobos. Since Tagish Lake is commonly used as a spectral analog for D-type asteroids, this provides additional support for compositional similarities between Phobos and D-type asteroids.
    The Astrophysical Journal 10/2013; 777:127. · 6.28 Impact Factor
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    ABSTRACT: We present a preliminary analysis of the craters on the asteroid Steins images obtained by OSIRIS, the imaging system on board the ESA mission ROSETTA, during the flyby on 5th September 2008. Steins has been observed at the closest distance of about 800 km achieving the maximum resolution of 80 m/px. Several small-to-medium craters have been identified, in addition to few very large craters: one of them is nearly 2 km across. The images show also the superposition of small craters on larger ones, and some structure that may represent the remnant of old degraded craters. A structure of chain-like craters has also been identified. All the craters have been counted in order to get the cumulative number per square km. Then we have applied our model to estimate the collisional age of Steins using the most recent modeling of the current population of the Main Belt asteroids (Bottke et al., 2005) to define the impactor flux. The model uses the scaling law of Holsapple and Housen (2007) to determine the crater diameter as a function of the impactor radius.
    41th DPS Meeting; 01/2013
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    ABSTRACT: The Martian satellite Phobos has been observed on 2007 February 24 and 25, during the pre- and post-Mars closest approach (CA) of the ESA Rosetta spacecraft Mars swing-by. The goal of the observations was the determination of the surface composition of different areas of Phobos, in order to obtain new clues regarding its nature and origin. Near-ultraviolet, visible and near-infrared (263.5-992.0 nm) images of Phobos's surface were acquired using the Narrow Angle Camera of the OSIRIS instrument onboard Rosetta. The six multi-wavelength sets of observations allowed a spectrophotometric characterization of different areas of the satellite, belonging respectively to the leading and trailing hemisphere of the anti-Mars hemisphere, and also of a section of its sub-Mars hemisphere. The pre-CA spectrophotometric data obtained with a phase angle of 19° have a spectral trend consistent within the error bars with those of unresolved/disc-integrated measurements present in the literature. In addition, we detect an absorption band centred at 950 nm, which is consistent with the presence of pyroxene. The post-CA observations cover from NUV to NIR a portion of the surface (0° to 43°E of longitude) never studied before. The reflectance measured on our data does not fit with the previous spectrophotometry above 650 nm. This difference can be due to two reasons. First, the OSIRIS observed area in this observation phase is completely different with respect to the other local specific spectra and hence the spectrum may be different. Secondly, due to the totally different observation geometry (the phase angle ranges from 137° to 140°), the differences of spectral slope can be due to phase reddening. The comparison of our reflectance spectra, both pre- and post-CA, with those of D-type asteroids shows that the spectra of Phobos are all redder than the mean D-type spectrum, but within the spectral dispersion of other D-types. To complement this result, we performed an investigation of the conditions needed to collisionally capture Phobos in a way similar to that proposed for the irregular satellites of the giant planets. Once put in the context of the current understanding of the evolution of the early Solar system, the coupled observational and dynamical results we obtained strongly argue for an early capture of Phobos, likely immediately after the formation of Mars.
    Monthly Notices of the Royal Astronomical Society 12/2012; 427:3230-3243. · 5.23 Impact Factor
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    ABSTRACT: Here we present some preliminary results on surface variegation found on (21) Lutetia from ROSETTA-OSIRIS images acquired on 2010-07-10. The spectrophotometry obtained by means of the two cameras NAC and WAC (Narrow and Wide Angle Cameras) is consistent with ground based observations, and does not show surface diversity above the data error bars. The blue and UV images (shortward 500nm) may, however, indicate a variegation of the optical properties of the asteroid surface on the Baetica region (Sierks et al., accepted for publication). We also speculate on the contribution due to different illumination and to different ground properties (composition or, more probably, grain size diversity). In particular a correlation with geologic units independently defined by Massironi et al. (this issue) is evident, suggesting that the variegation of the ground optical properties is likely to be real.
    Planetary and Space Science 06/2012; 66:43-53. · 1.63 Impact Factor
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    ABSTRACT: Context. The Jupiter-family comet 81P/Wild 2, target of the NASA Stardust mission, is very important in the context of the studies of pristine objects in the solar system. First, it was only recently deflected into the present orbit, having spent at least 300 yr at higher heliocentric distance prior to the orbital change in 1974. It is therefore likely that the comet experienced a recent activation with consequent low alteration of its original material. Second, it is the only comet whose coma material was brought back to Earth for laboratory analysis. We observed the object between 2010 February 9 and September 9 for a total of 11 nights during the 2010 perihelion passage. Aims: The goals of the campaign were the characterization of the comet's dust activity and the comparison with previous apparitions to derive hints on the secular behavior of the object. Methods: Broadband R- and I-images were acquired using three instruments: ALFOSC, CAMELOT, and TCP. The first one is mounted at the Nordic Optical Telescope on La Palma, while the second and the third are mounted at the Instituto de Astrofisica de Canarias 0.82-m telescope on Tenerife. We analyzed the presence and variability of dust structures in the coma with image-enhancing techniques, the radial profile of the dust brightness, and we measured the dust production rate and the dust reddening. Results: We found evidence of a long-lasting sunward fan and anti-solar tail activity throughout all our observations up to a heliocentric distance of 2.42 AU. Afρ measurements suggest a pre-perihelion peak of the activity, caused by a seasonal effect, plus two post-perihelion outbursts. Both spatial and Afρ radial profiles indicate a steady-state coma at nucleocentric distances greater than ~1000-2000 km. The color analysis reveals a moderately reddened dust with a 6-9%/1000 Å reddening, consistent with the current picture of cometary dust. The second outburst emitted dust with lower reddening. Conclusions: The comparison with previous perihelion passages points toward a recurrent main activity always driven by the same areas on the nucleus, producing dust with similar characteristics and in similar coma structures in different years. Our Afρ measurement at the longest heliocentric distance suggests the comet was less dust-productive in 2010, pointing toward a possible secular aging of the object and its activity. The change of dust colors during the unusual second outburst suggests that an internal part of the nucleus has different physical properties compared with those that produce the recurrent main activity, pointing toward a heterogeneous comet. This article is based on observations made with the 2.56-m Nordic Optical Telescope (NOT) and the 0.82-m IAC-80 Telescope. The NOT is operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. The 0.82-m IAC-80 Telescope is operated on the island of Tenerife by the Instituto de Astrofisica de Canarias in the Spanish Observatorio del Teide.
    Astronomy and Astrophysics 05/2012; 541:A159. · 4.48 Impact Factor
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    ABSTRACT: On the 25 of February 2007, the ESA Rosetta mission approached planet Mars. This gravity assist gave the opportunity to the scientific community to get several sets of images through the use of OSIRIS instrument: Rosetta imaging camera. The entire surface of the Red Planet has been imaged as well as the atmosphere and the clouds which were partly covering it. The aim of this paper is to introduce and show the preliminary studies which have concentrated on three images sets obtained during Rosetta closest approach to Mars.
    Memorie della Societa Astronomica Italiana Supplementi. 01/2012;
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    ABSTRACT: We present a method for analyzing the reflectance properties of atmosphereless bodies as asteroids and comet nuclei. The method is self-consistent, independent of the shape model of the object and can be easily applied for any space mission target. We used it for the E-type Main Belt asteroid (2867) Steins, observed from the OSIRIS-WAC camera onboard Rosetta spacecraft during a close approach on September 5, 2008. We investigate the reflectance dependence on phase angle which is interpreted in terms of the Hapke's theory of bidirectional reflectance. A deeper analysis allows to obtain an estimate of the typical size of the regolith grains. Steins regolith layer seems to be made of large, highly scattering iron-poor opaque silicate particles. The macroscopic roughness, probably influenced by the global irregular shape, appears fairly high, comparable with radar measurements of other E-type asteroids. Assuming an enstatite composition, we estimated a grain size of about 30-130 mu m and we noticed a correlation between grain size and wavelength, suggesting the existence of a grain size distribution, as expected from real surfaces. The comparison with more accurate calculations (Spjuth \textit{et al.}, 2009) shows that our simplified method is robust and reliable for a preliminary and shape-independent analysis of the reflectance properties of atmosphereless bodies.
    Memorie della Societa Astronomica Italiana Supplementi. 01/2012;
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    ABSTRACT: Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.
    Science 10/2011; 334(6055):487-90. · 31.48 Impact Factor
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    ABSTRACT: The ESA Rosetta mission, launched in 2004 March, will flyby the second asteroid target (21) Lutetia in 2010 July. This asteroid is quite different from (2867) Steins, encountered by Rosetta in 2008 September. Lutetia is in fact a much larger asteroid, approximately 100km of diameter, as compared to the 5 km of Steins and also its surface composition seems fairly different. A wide international ground-based observational campaign has been carried out and is still going on to obtain information on the object. In this context, we observed Lutetia four times spectroscopically in the visible region totally covering its rotational period. In this paper we have compared all our observations, in order to try to shed more light on its nature. Moreover, an analysis of the geometric configuration of Lutetia during the several observations has also been performed. Our paper points out small variations of reflectance over the surface, possibly due to a large crater. However, the nature of Lutetia remains still elusive, probably because it could be a transition object between X and C taxonomic classes, pointing out to the crucial values of the forthcoming flyby to clarify the situation. Therefore, all the information we have gathered and here discussed have been very useful also to better define the observational strategy of the asteroid by Rosetta.
    Monthly Notices of the Royal Astronomical Society 11/2010; 408:1433-1437. · 5.23 Impact Factor
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    ABSTRACT: Preface; 1. Galileo's telescopic observations: the marvel and meaning of discovery George V. Coyne, S. J.; 2. Popular perceptions of Galileo Dava Sobel; 3. The slow growth of humility Tobias Owen and Scott Bolton; 4. A new physics to support the Copernican system. Gleanings from Galileo's works Giulio Peruzzi; 5. The telescope in the making, the Galileo first telescopic observations Alberto Righini; 6. The appearance of the Medicean Moons in 17th century charts and books. How long did it take? Michael Mendillo; 7. Navigation, world mapping and astrometry with Galileo's moons Kaare Aksnes; 8. Modern exploration of Galileo's new worlds Torrence V. Johnson; 9. Medicean Moons sailing through plasma seas: challenges in establishing magnetic properties Margaret G. Kivelson, Xianzhe Jia and Krishan K. Khurana; 10. Aurora on Jupiter: a magnetic connection with the Sun and the Medicean Moons Supriya Chakrabarti and Marina Galand; 11. Io's escaping atmosphere: continuing the legacy of surprise Nicholas M. Schneider; 12. The Jovian Rings Wing-Huen Ip; 13. The Juno mission Scott J. Bolton and the Juno Science Team; 14. Seeking Europa's ocean Robert T. Pappalardo; 15. Europa lander mission: a challenge to find traces of alien life Lev Zelenyi, Oleg Korablev, Elena Vorobyova, Maxim Martynov, Efraim L. Akim and Alexander Zakahrov; 16. Atmospheric moons Galileo would have loved Sushil K. Atreya; 17. The study of Mercury Louise M. Prockter and Peter D. Bedini; 18. Jupiter and the other giants: a comparative study Thérèse Encrenaz; 19. Spectroscopic and spectrometric differentiation between abiotic and biogenic material on icy worlds Kevin P. Hand, Chris McKay and Carl Pilcher; 20. Other worlds, other civilizations? Guy Consolmagno, S. J.; 21. Concluding remarks Roger M. Bonnet; Posters; Author index; Object index.
    Proceedings of the International Astronomical Union 11/2010;
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    ABSTRACT: On July 10, 2010, the ESA Rosetta mission successfully flew by the asteroid 21 Lutetia, the biggest asteroid ever encountered by a space mission. The OSIRIS imaging system onboard Rosetta, equipped with a Narrow Angle Camera (NAC) and a Wide Angle Camera (WAC), observed the asteroid in 20 filters extending from 240 to 980 nm with a maximum spatial resolution of 60 m/px. Several color sequences were obtained at different rotational phases for the asteroid. Images with the Orange (647 nm) and OI (630 nm) filters of the NAC and WAC cameras were continously repeated to investigate the phase function in a wide phase angle range, from 0 to 156 degrees. In this work we will present unresolved spectrophotometry results, the albedo map and the phase function of 21 lutetia derived by the OSIRIS instrument. Potential albedo variations will be presented as well. We will finally discuss the implications for the mineralogy and the surface evolution of the asteroid.
    09/2010; 42:1032.
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    ABSTRACT: The majority of basaltic asteroids are found in the inner main belt, although a few have also been observed in the outer main belt and near-Earth space. These asteroids -referred to as V-types- have surface compositions that resemble that of the 530km sized asteroid Vesta. Besides the compositional similarity, dynamical evidence also links many V-type asteroids to Vesta. Moreover, Vesta is one of the few asteroids to have been identified as source of specific classes of meteorites, the howardite, eucrite, diogenite achondrites (HEDs). Despite the general consensus on the outlined scenario, several questions remain unresolved. In particular, it is not clear if the observed spectral diversity among Vesta, V-types and HEDs is due to space weathering, as is thought to be the case for S-type asteroids. In this paper, SDSS photometry is used to address the question of whether the spectral diversity among candidate V-types and HEDs can be explained by space weathering. We show that visible spectral slopes of V-types are systematically redder with respect to HEDs, in a similar way to what is found for ordinary chondrite meteorites and S-types. On the assumption that space weathering is responsible for the slope mismatch, we estimated an upper limit for the reddening timescale of about 0.5Ga. Nevertheless, the observed slope mismatch between HEDs and V-types poses several puzzles to understanding its origin. The implication of our findings is also discussed in the light of Dawn mission to Vesta. Comment: Accepted by ApJL
    The Astrophysical Journal Letters 09/2010; · 5.60 Impact Factor
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    ABSTRACT: We investigate the possible presence of heterogeneous surface features on asteroid (2867) Steins, using the G-mode multivariate statistical method (Coradini et al., 1977) applied to Rosetta/OSIRIS images. We analyze both NAC and WAC images obtained near around the closest approach that occurred on September 5th, 2008, through different filters centered on wavelengths ranging from 295 to 986 nm. The shape of Steins is modeled as a polyhedron of almost 58 000 facets. Photometric corrections were performed using Hapke's (2002) model to compensate for the variable illuminations conditions at the surface. The G-mode classification method was performed on all visible and illuminated facets, i.e. in a region limited to [−50°,+60°] in latitude and [−40°,+90°] in longitude, that represents almost 30% of the total surface. The analyzed set of facets does not show any significant difference in the reflected light content, suggesting no surface inhomogeneities larger than 4% at the 95% confidence level.
    Planetary and Space Science 07/2010; · 1.63 Impact Factor

Publication Stats

774 Citations
376.19 Total Impact Points

Institutions

  • 1995–2015
    • University of Padova
      • • Department of Industrial Engineering
      • • Department of Geosciences
      • • Centre for Studies and Activities for Space “G.Colombo” CISAS
      Padua, Veneto, Italy
  • 2008–2009
    • It-Robotics
      Vicenza, Veneto, Italy
  • 2005–2009
    • Università di Pisa
      Pisa, Tuscany, Italy
  • 2003
    • The Astronomical Observatory of Brera
      Merate, Lombardy, Italy
  • 2001
    • Instituto De Astrofisica De Andalucia
      Granata, Andalusia, Spain
  • 1994–1998
    • Observatoire de Paris
      Lutetia Parisorum, Île-de-France, France
  • 1997
    • Federal University of Rio de Janeiro
      Rio de Janeiro, Rio de Janeiro, Brazil
  • 1991
    • National Research Council
      Roma, Latium, Italy