Alessandro Frigeri

The NASA/Dawn mission has acquired unprecedented measurements of the surface of the dwarf planet Ceres, the composition of which is a mixture of ultra-carbonaceous material, phyllosilicates, carbonates, organics, Fe-oxides, and volatiles as determined by remote sensing instruments including the VIR imaging spectrometer. We performed a refined analysis merging visible and infrared observations of Ceres’ surface for the first time. The overall shape of the combined spectrum suggests another type of silicate not previously considered, and we confirmed a large abundance of carbon material. More importantly, by analyzing the local spectra of the organic-rich region of the Ernutet crater, we identified a reddening in the visible range, strongly correlated to the aliphatic signature at 3.4 µm. Similar reddening was found in the bright material making up Cerealia Facula in the Occator crater. This implies that organic material might be present in the source of the faculae, where brines and ...

Organic compounds occur in some chondritic meteorites, and their signatures on solar system bodies have been sought for decades. Spectral signatures of organics have not been unambiguously identified on the surfaces of asteroids, whereas they have been detected on cometary nuclei. Data returned by the Visible and InfraRed Mapping Spectrometer on board the Dawn spacecraft show a clear detection of an organic absorption feature at 3.4 micrometers on dwarf planet Ceres. This signature is characteristic of aliphatic organic matter and is mainly localized on a broad region of ~1000 square kilometers close to the ~50-kilometer Ernutet crater. The combined presence on Ceres of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and organic material indicates a very complex chemical environment, suggesting favorable environments to prebiotic chemistry.

Carbon dioxide (CO2) is one of the most abundant species in cometary nuclei, but because of its high volatility, CO2 ice is generally only found beneath the surface. We report the infrared spectroscopic identification of a CO2 ice-rich surface area located in the Anhur region of comet 67P/Churyumov-Gerasimenko. Spectral modeling shows that about 0.1% of the 80- by 60-meter area is CO2 ice. This exposed ice was observed a short time after the comet exited local winter; following the increased illumination, the CO2 ice completely disappeared over about 3 weeks. We estimate the mass of the sublimated CO2 ice and the depth of the eroded surface layer. We interpret the presence of CO2 ice as the result of the extreme seasonal changes induced by the rotation and orbit of the comet.

INTRODUCTIONThe surface of the dwarf planet Ceres is known to host phyllosilicate minerals, but their distribution and origin have not previously been determined. Phyllosilicates are hydrated silicates, and their presence on the surface of Ceres is intriguing given that their structure evolves through an aqueous alteration process. In addition, some phyllosilicates are known to bear NH4, which places a constraint on the pH and redox conditions during the evolution of Ceres. We studied the distribution of phyllosilicates across the planet’s surface to better understand the evolutionary pathway of Ceres.RATIONALEUsing the data acquired by the mapping spectrometer (VIR) onboard the Dawn spacecraft, we mapped the spatial distribution of different minerals on Ceres on the basis of their diagnostic absorption features in visible and infrared spectra. We studied the phyllosilicates through their OH-stretch fundamental absorption at about 2.7 µm and through the NH4absorption at about 3.1 µm...

Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov-Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of v...

ABSTRACT Vestarsquos spectrum has strong absorption centered near 0.9 and 1.9 $mu$m, indicative of Fe-bearing pyroxenes. Data from the Dawn VIR characterize and map the mineral distribution on Vesta, providing new insights into Vestarsquos formation and evolution.

ABSTRACT 4 Vesta has a surface of basaltic material (1) with strong absorption features centered near 0.9 and 1.9 μm, indicative of Fe-bearing pyroxenes. The spectra of HED (howardite, eucrite and diogenite) meteorites have similar features (1). This led to the hypothesis that Vesta was the parent body of the HED clan (2,3) and the discovery of a dynamical Vesta family of asteroids (Vestoids) provides a further link between Vesta and HEDs (4). Data from the Dawn VIR (Visible InfraRed mapping Spectrometer) (5,6) characterize and map the mineral distribution on Vesta, strengthen the Vesta - HED linkage and provide new insights into Vesta's formation and evolution.

The MARSIS observations are optimized during periods when the pericenter of the orbit is near or below zero degrees sun elevation (ldquonightsiderdquo) and the nightside phase, the last of the primary MEX mission, occurs on March-July 2005, in the northern latitude of MARS regions. This paper provides a description of the modeling approach and of the expected performance of the

In this paper we describe an inversion approach in order to analyze data from the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on Mars Express. The inversion process allows the dielectric constant of the subsurface material to be estimated provided the dielectric constant of the surface is known. In addition, if impurity are present, it is possible

ABSTRACT The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is the first radar to collect data from Mars orbit. MARSIS is a multi-frequency synthetic aperture orbital sounding radar. MARSIS acquires data in the conventional fashion of a radar in the range 0.1-5.5 MHz, which corresponds to wavelength of tens to hundreds of metres. These long wavelengths maximize the penetration of the signal into the subsurface of Mars. MARSIS has been configured to collect High Resolution Data in order to improve the science investigation of the North Polar Deposits of Mars (Planum Boreum). This special configuration provided data of unprecedented quality that contributed to the reconstruction of the three-dimensional structure of the icy North Polar Layered Deposits and of the enigmatic Basal Unit beneath. The processing of the achieved data show that the deepest MARSIS detection is at the bottom of the basal unit and is estimated to be around 3.3 Km in the vacuum and 2.4 Km in the medium. CONCLUSION: We successfully implemented an advanced setting of the on board software in order to boost the signal-to-noise ratio of measurements and above all to have an adequate set of contiguous and unprocessed data. This gave us the flexibility to improve the ground processing, choosing different size for the Synthetic Aperture Technique. Although this procedure pushed the instrument to the limit of its original design capabilities, performance was flawless.

ABSTRACT Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is an orbital subsurface sounder aboard ESA's Mars Express spacecraft . It transmits a low-frequency radar pulse that is capable of penetrating below the surface, and is reflected by subsurface dielectric discontinuities. MARSIS has been used to probe both the south and the north polar caps of Mars, revealing their thickness and structure. We report on the results of a campaign of observations of the north polar ice cap of Mars that took place between May and December 2011 in uniquely favorable conditions and produced data of unprecedented quality. The focus of this work is the so-called Basal Unit, a dark, ice-rich, complexely layered geologic unit lying stratigraphically between the polar layered deposits and the Vastitas Borealis Formation, and extending beneath most of Planum Boreum and Olympia Planitia. The objective of this work is the to study the full three dimensional structure of the Northern Polar Deposit and in particular of the Basal Unit (BU). It was recently found that the BU consists of two markedly different units, called the Rupes Tenuis unit and the Planum Boreum cavi unit. The Rupes Tenuis unit appears to be older, horizontally layered, and lacking erosional contacts. It has been thus interpreted as the result of precipitation and cold-trapping of dust-laden volatiles. The Planum Boreum cavi unit displays cross-bedding, indicating dune accumulation. Bright layers within it are interpreted as being made of ice-cemented dust, while dark layers should consist of weathered basalt fines. It seems likely that, in places, the Planum Boreum cavi unit rests directly on the Vastitas Borealis, without the Rupes Tenuis unit in between. Because the two units in the BU have formed much earlier than the north polar layered deposits, and at some interval from each other, they bear evidence of past climatic conditions that were very different from present, so that they "could potentially be a Rosetta Stone for the Martian climate". Subsurface sounding radar investigations by both MARSIS and SHARAD revealed that the BU has radar properties that are different from both the polar layered deposits and the Vastitas Borealis Formation, probably because of a mostly icy composition, but with a larger fraction of impurities than the polar layered deposits above. The upper surface of the BU exhibits significant relief, with features appearing to be erosional cutbacks and reentrants, indicating a complex accumulation history. Higher dust content and the resulting stronger attenuation is thought to be the reason why SHARAD radar signal could not penetrate through the BU and detect its bottom face. However, such a volume fraction cannot be much larger than the polar layered deposits, since MARSIS data revealed strong returns from the BU-Vastitas Borealis Formation interface, implying a relatively low fraction of impurities within the BU. From the summer phase of the Polar Campaign of data acquisition we have selected 161 radargrams. The radargrams were processed in order to cancel the effect of the ionosphere and to align the primary echo to a datum. The post-processed radargrams have been ingested into a Free Open Source software stack for geophysical imaging and interpretation. We find weak echoes within the BU that appear to outline a two-layer structure, perhaps corresponding to the Rupes Tenuis unit and the Planum Boreum Cavi unit. This was found through visual inspection, however, because echoes within the BU are too sporadic to be automatically picked, so further data processing and analysis is needed to confirm the result. As first results we found that the BU has a dielectric constant significantly greater than that of water ice, and thus that it contains a much larger dust fraction than the NPLD above them. We find, however, that no single value can produce the correct topographic relationship over the whole BU, which implies either that the topography of Planum Boreum beneath the polar cap is not a regular continuation of the topography outside the cap, or that the dielectric permittivity of the BU, and thus its dust content, is laterally inhomogeneous. Work to verify these two hypotheses is currently ongoing.

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on the Mars Express orbiter obtained data over the North Polar Layered Deposits (NPLD) and found that they were easily penetrated to their base by the radar signal, and that the deposits must be nearly pure ice. In addition, there was no evidence for deflection of the lower contact of the NPLD with the substrate, implying a thick elastic lithosphere beneath that sector of the NPLD. Here we report on new MARSIS observations of the South Polar Layered Deposits ...

Liquid water under Mars' southern ice cap Mars is known to host large quantities of water in solid or gaseous form, and surface rocks show clear evidence that there was liquid water on the planet in the distant past. Whether any liquid water remains on Mars today has long been debated. Orosei et al. used radar measurements from the Mars Express spacecraft to search for liquid water in Mars' southern ice cap (see the Perspective by Diez). They detected a 20-km-wide lake of liquid water underneath solid ice in the Planum Australe region. The water is probably kept from freezing by dissolved salts and the pressure of the ice above. The presence of liquid water on Mars has implications for astrobiology and future human exploration. Science , this issue p. 490 ; see also p. 448

The dwarf planet Ceres is known to host a considerable amount of water in its interior, and areas of water ice were detected by the Dawn spacecraft on its surface. Moreover, sporadic water and hydroxyl emissions have been observed from space telescopes. We report the detection of water ice in a mid-latitude crater and its unexpected variation with time. The Dawn spectrometer data show a change of water ice signatures over a period of 6 months, which is well modeled as ~2-km increase of water ice. The observed increase, coupled with Ceres' orbital parameters, points to an ongoing process that seems correlated with solar flux. The reported variation on Ceres' surface indicates that this body is chemically and physically active at the present time.

After the Mariner-10 mission to Mercury of the 1970s, the NASA MESSENGER [1] successfully acquired new data in its two fly-bys of December, 2007 and October, 2008. Moreover, the European and Japanese Space Agencies are preparing an upcoming mission to Mercury named BepiColombo [2]. In 1970s the common media for publishing maps was paper. Nowadays, the broad diffusion of computers connected through a network allows scientists to acquire digital data directly, improving their possibilities of analysis and interpretation. In general the amount of details and the extents of a map are limited by the physical size of the media. In the case of paper maps the scale factor is used as the value that limits the details and the extents of the map to a usable physical size of the sheet, so the planetary surfaces have been divided in quadrangles taking into account the scale and the actual area covered. In digital systems the limiting factor is the capacity of the storage media. With digital maps...

Introduction The Dawn mission to Vesta has greatly improved the quality and resolution of data available to explore the asteroid. Prior to the Dawn mission the best data available was the one from Hubble Space Telescope [1-6] with a maximum resolution of 50 km per pixel. The survey phase of the mission has pushed spatial resolution up to about 100 meters per pixel by the Framing Camera (FC, [7]) on-board Dawn, and 700 meters per pixel for the VIR spectrometer, spanning the spectral range from the visible to infrared at 0:25

A. Frigeri (1), M.C. De Sanctis (1), E. Ammannito (1), R. A. Yingst (2), S. Mest (2), F. Capaccioni (1), B. Garry (2), G. Magni (1), E. Palomba (1), N. Petro (3), F. Tosi (1), D. Williams (4), F. Zambon (1), R. Jaumann (5), C.M. Pieters (6), C.A. Raymond (7), C.T. Russell (8) and the Dawn Team; (1) Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, via del Fosso del Cavaliere, 00133 Roma, Italy (alessandro.frigeri@ifsi-roma.inaf.it); (2) Planetary Science Institute, Tucson, Arizona, USA; (3) NASA Goddard Space Flight Center, Greenbelt, MD; (4) Arizona State University, Tempe, AZ; (5) DLR, Berlin, Germany; (6) Department of Geological Sciences, Brown University, Providence, Rhode Island, USA; (7) NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA; (8) Institute of Geophysics and Planetary Physics, University of California at Los Angeles, Los Angeles, California, USA;

MISSION. A. Frigeri, M.C. De Sanctis, E. Ammannito, G. Carrozzo, D. Williams, S. Mest, D. Buczkowski, F. Preusker, R. Jaumann, T. Roatsch, J. Scully, T. Kneissl, C.A. Raymond, C.T. Russell. Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, via del Fosso del Cavaliere, 00133 Roma, Italy (alessandro.frigeri@iaps.inaf.it); Institute of Geophysics and Planetary Physics, University of California at Los Angeles, Los Angeles, California, USA; Arizona State University, Tempe, AZ; Planetary Science Institute, Tucson, Arizona, USA; German Aerospace Center (DLR), Berlin, Germany; JHU Applied Physics Laboratory Laurel, Maryland, USA; NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA; Freie Universitt Berlin, Malteserstr. 74-100, 12249 Berlin, Germany;

The need of electronic data to be inserted in geospatial databases lead us to develop a simple Personal Digital Assistant (PDA) based eld log system to store punctual data to be imported directly in GRASS as a site-le. The application communicates with a GPS unit so positional data are automatically stored, allowing the user to input only categorical data. The system frame has been chosen so that the overall cost of a basic system is very low but no changes are required to use it with professional GPS units and dieren t PDA systems. The software is released under the terms of GPL license so that everyone could improve it or adapt it to his own eld logging campaign.

The availability of large volume of data from instruments on-board scientific planetary missions justify the use of Geographic Information Systems (GIS) procedures for the study of terrestrial planets and their satellites. As mission data volumes increase the use of GIS techniques offer the planetary scientist a way for fast retrieval, storage and analysis of heterogeneous data and allows comparative analysis between different dataset that otherwise would be difficult to perform. Although GIS systems have been already used for planetary research, none provides a native generic support for studying surfaces of terrestrial planets and satellites. The work presented here describes the development of a pool of procedures in the form of computer codes and supporting files produced to provide a generic support to handle, analyze and visualize planetary remote sensed data in a selected GIS system allowing to perform the comparative analysis of different geological and geophysical planetary...

The numerous missions to Mars have sent information about the red planet during last decades. Recently it has been shown that Mars has ice on its poles and that ice could be probably present all over the planet subsurface. The presence of ice on subsurface could drive particular geological structures. The so called ’wrinkle ridges’ structures could be related to this. Grass GIS has been used to import and store in a common geospatial database Viking image data and the latest Mars Global Surveyor (MGS) data. GRASS raster based analysis at dieren t resolution has been used to identify wrinkle structures. The image modules are used to align Viking data with Mars Orbiter Laser Altimeter (MOLA) DEM. 1 Introduction The large quantity of data coming from missions to Mars made necessary to deal with an ecien t system of storage/retrieval of these data. Planetary Data System (PDS) represents a good example of distributed archiving system. The analysis of the data is thereafter dicult due to ...

1 Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, via del Fosso del Cavaliere, 00133 Roma, Italy (alessandro.frigeri@iaps.inaf.it); 2 Institute of Geophysics and Planetary Physics, University of California at Los Angeles, Los Angeles, California, USA; 3 Planetary Science Institute, Tucson, Arizona, USA; 4 Arizona State University, Tempe, AZ; 5 DLR, Berlin, Germany; 6 Department of Geological Sciences, Brown University, Providence, Rhode Island, USA; 7 NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA;

The prole recognition and polygon breaking (PPA) algorithm allows to extract the ridge and valley axes automatically over wide areas maps. The algorithm simulates the human thinking in the line drawing process. First a process of prole recognition takes all the points close to the possible axes and connects them as a belt of closed polygons. The polygons are then broken into a continuous line and a smoothing algorithm adjusts the line. The algorithm, originally coded in Fortran, has been adapted to be used for raster analysis in Grass. The module takes a raster map, typically a DEM, and outputs a vector le representing the ridge or the valley axes. Various testings show the features of the algorithm and the implementation into Grass GIS.

ABSTRACT L’informazione geografica è ormai entrata a far parte della vita quotidiana. Capire e conoscere gli strumenti utili per gestire informazioni territoriali è quindi una necessità per i professionisti e tecnici che operano sul territorio, ma anche per gli studenti di materie ambientali, urbanistiche o comunque legate alla pianificazione territoriale e alla protezione civile. Il presente testo ha lo scopo di introdurre il lettore al mondo dei software GIS e in particolare all’uso di alcuni software geografici Liberi ed Open Source (GRASS GIS, Quantum GIS o QGIS, SpatiaLite). Il testo fornisce nozioni di carattere generale sulla cartografia numerica e sui sistemi di riferimento. Gli autori sono tra i massimi esponenti e protagonisti a livello internazionale in campo di GIS open source. L'originalità dell'opera è da ricercarsi nella possibilità, da parte dell’utente, di avvalersi immediatamente sia degli strumenti software che delle numerose risorse documentali accessibili via internet e descritte nel volume. Vengono descritti i sistemi di riferimento e si assiste l’utente nell’installazione dei software su sistemi operativi Microsoft, Apple, GNU/Linux. Sono inoltre introdotte le funzionalità più importanti di software ben noti come QGIS o GRASS GIS e si forniscono le modalità di approccio alla gestione del dato geografico mediante motori di database relazionali (SpatiaLite).

ABSTRACT Planning observations during an ongoing planetary scientific mission represents an important and delicate task, as every byte of data from these projects embodies huge personnell efforts and investments. While specific tools are usually provided within almost every instrument or mission, we propose a more generic approach that enables to plan future observation using the experience and skills acquired during the scientific observations up to the moment of planning. The use of Geographic Information Systems (GIS) is spreading among planetary sciences [1] as they offer unique capabilities for geospatial analysis of a wide range of data products. Within the VIR/Dawn team, we have worked on methods to use GRASS GIS [2] as a planning tool for future observations.

ABSTRACT We describe a method to estimate the total electron content (TEC) of the Mars ionosphere from the output parameters of an algorithm, called the Contrast Method (Picardi, G., Sorge, S. [2000]. Proc. SPIE. Eighth International Conference on Ground Penetrating Radar, vol. 4084, pp. 624–629; Ilyushin, Ya.A., Kunitsyn, V.E. [2004]. J. Commun. Technol. Electron. 49, 154–165), which allows to correct the phase distortion of the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi, G. et al. [2005]. Science 310, 1925–1928) in its subsurface mode. Based on the TEC values evaluated during 6 years of MARSIS activity, corresponding to about 4600 orbits, in this paper we present a global map of the night side TEC variations, which correlates well with the magnetic field model derived from Mars Global Surveyor (MGS) Magnetometer/Electron Reflectometer (MAG/ER) data. In particular, we demonstrate that regions of enhanced TEC preferentially correspond to areas where crustal magnetic field lines are quasi perpendicular to the martian surface; moreover, we demonstrate that, in regions where the magnetic field is predominantly nearly vertical, enhanced TEC values correlate with higher field intensities, while in regions where the magnetic field is predominantly nearly horizontal, such correlation is not observed. As already suggested in the past by other authors, we suggest that increased TEC values may be related to the precipitation of electrons from the martian magnetospheric tail along vertical crustal magnetic field lines.

At 525 km in mean diameter, Vesta is the second-most massive and one of the brightest asteroids of the main-belt. Here we give a global view of the bright material units on Vesta. We classified the BMs according to the normal visual albedo. The global albedo map of Vesta allows to be divided the surface into three principal types of terrains: bright regions, dark regions and intermediate regions. The distribution of bright regions is not uniform. The mid-southern latitudes contain the most bright areas, while the northern hemisphere is poor in bright regions. The analysis of the spectral parameters and the normal visual albedo show a dependence between albedo and the strength of ferrous iron absorption bands, strong bands correspond with high albedo units. Vesta's average albedo is 0.38, but there are bright material whose albedo can exceed 0.50. Only the E-Type asteroids have albedos comparable to those of the BMs on Vesta. The Dawn mission observed a large fraction of Vesta's surface at high spatial resolution, allowing a detailed study of the morphology and mineralogy of it. In particular, reflectance spectra provided by the Visible and InfraRed spectrometer , confirmed that Vesta's mineralogy is dominated by pyroxenes. All Vesta spectra show two strong absorption bands at approx 0.9 and 1.9 micron, typical of the pyroxenes and associated with the howardite, eucrite and diogenite meteorites.

Data from the Dawn VIR (Visible InfraRed mapping Spectrometer) instrument [1, 2] have been used to characterize and map the mineral distribution on Vesta. The results strengthen the Vesta - HED linkage and provide new insights into Vesta's formation and evolution.

4 Vesta has a surface of basaltic material (1) with strong absorption features centered near 0.9 and 1.9 $\mu$m, indicative of Fe-bearing pyroxenes. The spectra of HED (howardite, eucrite and diogenite) meteorites have similar features (1). This led to the hypothesis that Vesta was the parent body of the HED clan (2,3) and the discovery of a dynamical Vesta family of asteroids (Vestoids) provides a further link between Vesta and HEDs (4). Data from the Dawn VIR (Visible InfraRed mapping Spectrometer) (5,6) characterize and map the mineral distribution on Vesta, strengthen the Vesta - HED linkage and provide new insights into Vesta's formation and evolution.

The Dawn spectrometer, VIR-MS (Visible and InfraRed Mapping Spectrometer), acquired data during Approach, Survey, High Altitude Mapping Orbit (HAMO) and Low Altitude Mapping Orbit (LAMO) covering a large part of Vesta's surface [1]. VIR provides data in two distinct channels: visible (0.25 - 1 $\mu$m) and infrared (0.95 - 5.02 $\mu$m), producing hyperspectral cubes of 432 bands for each channel [2]. The data obtained allow to investigate the mineralogical composition of the asteroid surface. Here we present a spectral analysis of the bright materials on Vesta.

We study the possibility to discern the infrared spectral signature of olivine in pyroxene based multimineralic mixtures. Different spectral indexes are selected and tested onto laboratory controlled spectral set of mixtures. The best index able to detect even low amount of olivines, will be applied to the VIR-Dawn dataset to search for olivine on the surface of Vesta.

The analysis of the whole disk of Vesta gives a global overview of its surface. We have classified the whole disk image of Vesta normalized at 550 nm with an ISODATA classifier and we have compared this result with a RGB image (R: 0.44 \textbackslashmicrom, G: 0.75 \textbackslashmicrom, B: 1 \textbackslashmicrom).

Analysis of band depth as a function of the phase angle show a clear positive correlation. This result, although supported by similar data from the Framing Camera, is intriguing as it is contrary to the expectations from radiative transfer theories.

Vesta\textbackslashrsquos spectrum has strong absorption centered near 0.9 and 1.9 $\mu$m, indicative of Fe-bearing pyroxenes. Data from the Dawn VIR characterize and map the mineral distribution on Vesta, providing new insights into Vesta\textbackslashrsquos formation and evolution.

L'esplorazione di Marte ha destato sempre molto interesse per la forte somiglianza all'orografia terrestre: vulcani, canyon, valli fluviali, crateri, plateu. I dati delle numerose missioni precedenti hanno permesso di identificare inequivocabilmente forme del rilevo tipiche del trasporto fluviale, o comunque della presenza di acqua. I dati a disposizione fino ad ora non permettono di sapere con esattezza quali sono i motori dell'evoluzione tettonica del pianeta, n{\`e} se Marte sia un pianeta tettonicamente attivo. La missione Mars Express permetter{\`a} l'avanzamento della conoscenza in questi ambiti e per la prima volta tenter{\`a} di rilevare la presenza di acqua nei primi chilometri di crosta con lo strumento italiano MARSIS: il ``Mars Advanced Radar for Subsurface and Ionososphere Sounding''. Il contributo all'esperimento MARSIS del Dipartimento di Scienze della Terra dell'Universit{\`a} degli studi Perugia prevede l'utilizzo del GIS GRASS per fornire al Science Team dati topografici per le simulazione della risposta del Radar e dati geologici per l'impostazione dei modi operativi.

Abstract Dwarf planet Ceres is characterized by several sites hosting (or have hosted) ice-rich patches as revealed by the Dawn's Visible and InfraRed spectrometer. The study of the illumination conditions including the effects of the local topography become critical in the estimation of the ice lifetime as well as the water vapor production rate. In this work we applied a 3-D thermophysical model in order to study the illumination conditions on the shape model, derived on the basis of the images acquired by the Dawn's Framing Camera during the Survey mission phase, and to calculate the surface temperatures and water sublimation rates. We are interested in a crater in the northern hemisphere (42°), Oxo, which hosts water ice in its southern wall. A comparison with the surface temperatures and water sublimation rates of another Ceres' crater, Juling, is carried out. Water ice sublimation rate of its ice-rich patch suggests that the Oxo crater probably is not the source of the emission detected by Herschel, a source that could be represented instead by the Juling crater.