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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2010.07.023 Byline: M.L. Moriconi (a), J.I. Lunine (b)(e), A. Adriani (b), E. D'Aversa (b), A. Negrao (b)(c), G. Filacchione (d), A. Coradini (b) Keywords: Titan; Satellites, Surfaces; Infrared observations; Image processing Abstract: Liquid hydrocarbons were long predicted on Titan's surface before the RADAR instrument onboard Cassini detected lakes poleward of 70[degrees]N in July 2006. Before that the Cassini Imaging Science Subsystem (ISS) observed a lake-like feature in the South Pole, named Ontario Lacus, in July 2004. Here we analyze one observation of Ontario Lacus taken by the Visual and Infrared Mapping Spectrometer (VIMS) on 2007 December 5, during the T 38 flyby. This is the best spatially resolved image of a Titan lake to date by an imaging spectrometer, and has been previously reported in Brown et al. (Brown, R.H., Soderblom, L.A., Soderblom, J.M., Clark, R.N., Jaumann, R., Barnes, J.W., Sotin, C., Buratti, B., Baines, K.H., Nicholson, P.D. [2008]. Nature 454, 607-610) and in Barnes et al. (Barnes, J.W. et al. [2009]. Icarus 201, 217-225). The observing geometry and our data processing will be explained, followed by a discussion of the main characteristics of the image. The analyzed image covers a small portion of Ontario Lacus and shows what appears from RADAR data to be a region of modest slope ('ramp') adjacent to the dark lake itself. Our analysis of 5.0[mu]m spectral data suggests that the previously reported absorption feature of ethane seen at shorter wavelengths may be produced by damp sediments adjacent to the main liquid basin. The latter appears to be absorbing all of the photons incident upon it in the 5[mu]m spectral region and shows no discernible absorption features. A characterization of the basin composition and morphology is developed with the help of ISS and RADAR observations. The simplest model consistent with the data is an optically deep lake surrounded by a region in which ethane, propane, possibly methane, and other, less volatile hydrocarbons and nitriles are present mixed into spectroscopically neutral sediments. The dominance of relatively low vapor pressure organics outside the lake itself suggests a retreat of Ontario Lacus associated with evaporation on seasonal or longer timescales, consistent with analysis of RADAR and ISS images. Author Affiliation: (a) Institute of Atmospheric Science and Climate-CNR, Via Fosso del Cavaliere 100, I-00133 Rome, Italy (b) IFSI-INAF, Via Fosso del Cavaliere 100, I-00133 Rome, Italy (c) Escola Superior de Tecnologia e Gestao de Leiria, Campus 2, Morro do Lena-Alto do Vieiro, P-2411 Leiria, Portugal (d) IASF-INAF, Via Fosso del Cavaliere 100, I-00133 Rome, Italy (e) Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy Article History: Received 15 October 2009; Revised 22 July 2010; Accepted 27 July 2010

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.07.022 Byline: F. Altieri (a), L. Zasova (b), E. D'Aversa (a), G. Bellucci (a), F.G. Carrozzo (a), B. Gondet (c), J.-P. Bibring (c) Keywords: Mars; Atmosphere; Atmosphere; Composition; Spectroscopy Abstract: We present a method to derive the 2D maps of the O.sub.2 (a.sup.1 [DELTA].sub.g) airglow emission at 1.27[mu]m from the OMEGA/MEx nadir observations. The OMEGA imaging capabilities allow monitoring the 2D distribution, daily and seasonal variation of the O.sub.2 emission intensities with a detection limit of 4 MR. The highest values, of the order of [approximately equal to]31 MR, are found on the south pole for 11h Atmospheric waves crossing the terminator on the southern polar regions are observed for the first time during the MY28 early spring. The spatial scale of the waves ranges from 100 to 130km, and the intensity fluctuations are of the order of 4MR. This study confirms the high potentiality of O.sub.2 (a.sup.1 [DELTA].sub.g) day glow as a passive tracer of the martian atmosphere dynamics at high latitudes. Author Affiliation: (a) IFSI - INAF, Via del Fosso del Cavaliere 100, 00133 Rome, Italy (b) Space Research Institute, 84/32 Profsoyuznaya Str., 117997 Moscow, Russia (c) Institut d'Astrophysique Spatiale, BAcentst. 121, Universite Paris-Sud, 91405 Orsay Cedex, France Article History: Received 22 July 2008; Revised 18 June 2009; Accepted 6 July 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.05.020 Byline: F.G. Carrozzo (a), G. Bellucci (a), F. Altieri (a), E. D'Aversa (a), J.-P. Bibring (b) Keywords: Mars; Mineralogy; Ices; Frost; Spectroscopy Abstract: This paper reports on mapping of water frost and ice on Mars, in the range of latitudes between 30[degrees]S and 30[degrees]N. The study has been carried out by analysing 2485 orbits acquired during almost one martian year by the Mars Express/OMEGA imaging spectrometer. Water frost/ice is identified by the presence of [approximately equal to]1.5[mu]m, [approximately equal to]2[mu]m and [approximately equal to]3.0[mu]m absorptions. Although the orbits analysed in this study cover all seasons, water frost/ice is observed only near the aphelion seasons, at Ls=19[degrees] and at Ls=98-150[degrees]. Water frost/ice is detected mainly on the southern hemisphere between 15[degrees]S and 30[degrees]S latitude while it has not been identified within 15[degrees]S-15[degrees]N. In the northern hemisphere, the water frost/ice detection is complicated by the presence of clouds. Usually, water frost/ice is found in shadowed areas, while in few cases it is exposed to the sunlight. This indicates a clear relationship with the local illumination conditions on the slopes which favour the water frost/ice deposition on the surface when the temperatures are very low. OMEGA observations span from 10 to 17LT and the frost/ice is detected mainly between 15 and 16LT, with practically no detection before 13LT. We think this is due to the fact that the 10-12LT observations occur at large distances and it is not a local time effect. A thermal model is used to determine the deposition conditions on the sloped surfaces where water frost/ice has been found. There, daily atmospheric saturation does not occur on pole facing 10-25[degrees] slopes with current water vapour abundances but only by assuming values greater than 40pr[mu]m. Moreover, the water frost/ice is not detected during the northern winter, even if the thermal model foresees daily saturation on 25[degrees] slopes. Author Affiliation: (a) Istituto Nazionale di Astrofisica - Istituto Fisica Spazio Interplanetario (IFSI), Via del Fosso del Cavaliere 100, 00133 Rome, Italy (b) Institut d'Astrophysique Spatiale (IAS), BAcentstiment 121, Universite Paris Sud, 91405 Orsay Cedex, France Article History: Received 12 January 2009; Revised 4 May 2009; Accepted 23 May 2009

Saturn's icy satellites are among the main scientific objectives of the Cassini-VIMS (Visual and Infrared Mapping Spectrometer) experiment. This paper contains a first systematic and comparative analysis of the full-disk spectral properties of Dione, Enceladus, Epimetheus, Hyperion, Iapetus, Mimas, Phoebe, Rhea and Tethys as observed by VIMS from July 2004 to June 2005. The disk integrated properties (350-5100 nm reflectance spectra and phase curves at 550-2232 nm) and images of satellites are reported and discussed in detail together with the observed geometry. In general, the spectra in the visible spectral range are almost featureless and can be classified according to the spectral slopes: from the bluish Enceladus and Phoebe to the redder Iapetus, Hyperion and Epimetheus. In the 1000-1300 nm range the spectra of Enceladus, Tethys, Mimas and Rhea are characterized by a negative slope, consistent with a surface largely dominated by water ice, while the spectra of Iapetus, Hyperion and Phoebe show a considerable reddening pointing out the relevant role played by darkening materials present on the surface. In between these two classes are Dione and Epimetheus, which have a fiat spectrum in this range. The main absorption bands identified in the infrared are the 1520, 2020, 3000 nm [H.sub.2]O/OH bands (for all satellites), although Iapetus dark terrains show mostly a deep 3000 nm band while the 1520 and 2020 nm bands are very faint. In this spectral range, the Iapetus spectrum is characterized by a strong reddening. The C[O.sub.2] band at 4260 nm and the Fresnel ice peak around 3100 nm are evident only on Hyperion, Phoebe and Iapetus. The phase curves at 550 and at 2232 nm are reported for all the available observations in the 0[degrees]-144[degrees] range; Rhea shows an opposition surge at visible wavelengths in the 0.5[degrees]-1.17[degrees] interval. The improvement on the retrieval of the full-disk reflectance spectra can be appreciated by a direct comparison with ground-based telescopic data available from literature. Finally, data processing strategies and recent upgrades introduced in the VIMS-V calibration pipeline (flat-field and destriping-despiking algorithm) are discussed in appendices. Keywords: Saturn, satellites; Spectroscopy; Infrared observations; Image processing

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2005.12.022 Byline: V. Formisano (a), A. Maturilli (a), M. Giuranna (a), E. D'Aversa (a), M.A. Lopez-Valverde (b) Keywords: Mars; Mars; atmosphere; Atmospheres; composition Abstract: We report on PFS-MEX (Planetary Fourier Spectrometer on board Mars Express) limb observations of the non-Local Thermodynamic Equilibrium emission by CO and CO.sub.2 isotopic molecules. The CO emission is observed peaking at altitudes lower than the CO.sub.2 emission peak. Two orbits have been considered, which explore latitudes from 75 to 15[degrees] N, located in local time at 11:30 and 06:40, and with L.sub.s=138[degrees] and 168[degrees], respectively. In general in the season considered (northern summer) the emission intensity increases going to lower latitudes. The peak emission height is also decreasing with decreasing latitude. The CO.sub.2 isotopic molecules are emitting radiance out of proportion with respect to the normal isotopic abundance, which surely indicates a strong contribution from a large number of much weaker CO.sub.2 bands, a result that will demand careful theoretical modeling. By comparison with Hitran data base we can identify, among the emitting bands, the second hot band for the 626 and 636 molecule, while for the 628 and 627 emission from the third hot bands are very possible. Other minor bands or lines are also observed in emission for the first time in Mars. In one of the two orbits considered, the orbit 1234 of MEX, we also observe at altitudes 80-85 km scattered radiation, with indication of CO.sub.2 ice aerosols as scattering centers. At the same altitude the Pathfinder descending measurements show a temperature that allows CO.sub.2 condensation. Pathfinder measurements were at 03:00 local time, while our observations are for orbit 1234 showing CO.sub.2 ice signature at 11:30 local time. These non-LTE limb emissions, with their unprecedented spectral resolution in this portion of the near infrared and their sensitivity and geographical coverage, will represent in our opinion an excellent data set for testing current theoretical models of the martian upper atmosphere. Author Affiliation: (a) Istituto di Fisica dello Spazio Interplanetario IFSI-INAF, Via del Fosso del Cavaliere 100, 00113 Roma, Italy (b) Instituto de Astrofisica de Andalucia (CSIC), Apdo. 3004, 18080 Granada, Spain Article History: Received 23 May 2005; Revised 20 December 2005

During the Cassini-Jupiter flyby, VIMS observed Io at different phase angles, both in full sunlight and in eclipse. By using the sunlight measurements, we were able to produce phase curves in the visual through all the near infrared wavelengths covered by the VIMS instrument (0.85-5.1 [micro]m). The phase angle spanned from ~2[degrees] to ~120[degrees]. The measurements, done just after Io emerged from Jupiter's shadow, show an increase of about 15% in Io's reflectance with respect to what would be predicted by the phase curve. This behavior is observed at wavelengths > 1.2 [micro]m. Moreover, just after emergence from eclipse an increase of about 25% is observed in the depth of S[O.sub.2] frost bands at 4.07 and 4.35 [micro]m. At 0.879 < [lambda] < 1.04 [micro]m the brightening is 10-24%. Below [lambda] = 0.879 [micro]m the brightening, if present, should be less than the precision of our measurements (~5%). Apparently, these observations are not explained neither by a diverse spatial distribution of S[O.sub.2] on the Io' surface nor by atmospheric S[O.sub.2] condensation on the surface during the eclipse. Keywords: Io; Atmosphere; Infrared observations: Satellites of Jupiter

We report unusual and somewhat unexpected observations of the jovian satellite Io, showing strong methane absorption bands. These observations were made by the Cassini VIMS experiment during the Jupiter flyby of December/January 2000/2001. The explanation is straightforward: Entering or exiting from Jupiter's shadow during an eclipse, Io is illuminated by solar light which has transited the atmosphere of Jupiter. This light, therefore becomes imprinted with the spectral signature of Jupiter's upper atmosphere, which includes strong atmospheric methane absorption bands. Intercepting solar light refracted by the jovian atmosphere, Io essentially becomes a 'mirror' for solar occultation events of Jupiter. The thickness of the layer where refracted solar light is observed is so large (more than 3000 km at Io's orbit), that we can foresee a nearly continuous multi-year period of similar events at Saturn, utilizing the large and bright ring system. During Cassini's 4-year nominal mission, this probing technique should reveal information of Saturn's atmosphere over a large range of southern latitudes and times. Keywords: Occultations; Jupiter; Infrared observations

Abstract Radiative transfer (RT) modelling of planetary atmospheres allows to obtain extremely valuable information about these environments. The computation of optical properties of the aerosols and gases, that is heavily time consuming, is always required as input for both forward models and inversion algorithms. We provide look up tables for these coefficients, ready to be ingested in RT solvers, in the visible and near infrared spectral ranges and covering the main species of the Solar System planets' atmospheres. Gases absorption coefficients have been computed with the line-by-line approach from the HITRAN 2012 spectral database and an improved method to interpolate them is suggested. Aerosols single scattering properties have been computed using the Mie and Rayleigh models for a set of selected species relevant for planetary atmospheres. Optimization in terms of tabulated wavelengths and maximum number of Legendre polynomial expansion terms has been performed for each species. Highlights • Development of databases of aerosols and gases properties for radiative transfer applications. • Improved interpolation method for gases absorption coefficients. • Applicability of the developed databases to studies related to the atmospheres of the Solar System planets. [ABSTRACT FROM AUTHOR]

During Cassini – Jupiter flyby occurred in December 2000, Visual–Infrared mapping spectrometer (VIMS) instrument took several image cubes of Jupiter at different phase angles and distances. We have analysed the spectral images acquired by the VIMS visual channel by means of a principal component analysis technique (PCA). The original data set consists of 96 spectral images in the 0.35–1.05 μm wavelength range. The product of the analysis are new PC bands, which contain all the spectral variance of the original data. These new components have been used to produce a map of Jupiter made of seven coherent spectral classes. The map confirms previously published work done on the Great Red Spot by using NIMS data. Some other new findings, presently under investigation, are presented. [Copyright &y& Elsevier]

In this paper, we detail the retrieval methods developed for the analysis of the spectral data from the JIRAM experiment on board of the Juno NASA mission [1], operating in orbit around Jupiter since July 2016. Our focus is on the analysis of the thermal radiation in the 5 µm transparency window in regions of lesser cloud opacity (namely, hot-spots). Moving from the preliminary analysis presented in [2], a retrieval scheme has been developed and implemented as a complete end-to-end processing software. Performances in terms of fit quality and retrieval errors are discussed from tests on simulated spectra, while some example and issue from usage on actual Jupiter data are also discussed. Following the suggestion originally presented in [3] for the analysis of the data from the Near Infrared Mapping Spectrometer (NIMS) on board of the NASA Galileo spacecraft, the state vector to be retrieved has been drastically simplified on physically sounding basis, aiming mostly to distinguish between the 'deep' content of minor gaseous components (H 2 O, NH 3 , PH 3 ) and their relative humidity or fractional scale height in the upper troposphere. The retrieval code is based on a Bayesian scheme [4], complemented by simulated annealing method for most problematic cases. The key parameters retrievable from JIRAM individual spectra are the NH 3 and PH 3 deep contents, the H 2 O vapor relative humidity as well as the total aerosol opacity. Limitations related to the approximations of forward model methods are also assessed quantitatively. [ABSTRACT FROM AUTHOR]

Abstract: Imaging spectrometers are highly effective instruments for investigation of planetary atmospheres. They present the advantage of coupling the compositional information to the spatial distribution, allowing simultaneous study of chemistry and dynamics in the atmospheres of Venus and Mars. In this work, we summarize recent results about the O2(a1 Δ g) night and day glows, respectively obtained by VIRTIS/Venus Express and OMEGA/Mars Express, the imaging spectrometers currently in orbit around Venus and Mars. The case of the O2(a1 Δ g – X3 Σ g −) IR emission at 1.27μm on the night side of Venus and the day side of Mars is analyzed, pointing out dynamical aspects of these planets, like the detection of gravity waves in their atmospheres. The monitoring of seasonal and daily airglow variations provides hints about the photochemistry on these planets. [Copyright &y& Elsevier]

Jupiter’s atmosphere presents limited regions of relatively thin cloud coverage (the so-called ‘hot spots’), which allow thermal radiation by warmer, deeper atmospheric layers to be transmitted directly to space. Hot spots therefore represent a means for probing physical conditions (namely chemical composition) below the main aerosol deck. Forthcoming missions to the Jovian system – Juno and EJSM spacecrafts – will host as payload components spectro-imagers operating in the infrared. Their coverage of 5μm CH4 transparency windows make them particularly suitable for the investigation of hot spots. This study is an assessment of their retrieval capabilities on the evaluation of gaseous mixing ratios from nighttime observations, on the basis of Bayesian theory. The retrieval performance is evaluated for the JIRAM instrument, a confirmed payload component of Juno. Its data will provide effective constraints on the mixing ratios of water vapor between 40 and 70km below the reference 1bar pressure level (between 3.5 and 7bars). Assuming an a priori correlation length equal to half the scale height, we achieve a minimum retrieval uncertainty of 0.17, once the mixing ratio is given in terms of log10(α), with α being the adimensional mixing ratio (vs. altitude) relative to a given reference profile. The JIRAM-Juno dataset will further allow determination of the ammonia mixing ratio, with a minimum relative retrieval uncertainty of 0.32 in the same altitude range, and of the phosphine mixing ratio, with comparable uncertainty up to the reference altitude. The retrieval performance is evaluated for a second instrument VIRHIS, which is a proposed payload component of Jupiter Ganymede Orbiter (JGO), one of the two spacecrafts of Europa-Jupiter System Mission (EJSM). This instrument has the benefit of higher spectral resolution and extended spectral range, when compared to JIRAM-Juno. Evaluation of the water vapor retrieval shows the uncertainty would be reduced to 0.08 with VIRHIS. The ammonia retrieval range would be expanded up to 10km (0.66bar), with a minimum uncertainty value of 0.10. Both instruments will place these measurements in a spatial context due to their simultaneous imaging capabilities, enabling therefore a number of studies covering chemical and dynamical aspects of atmospheric evolution. [Copyright &y& Elsevier]

Abstract: Titan''s bulk density along with Solar System formation models indicates considerable water as well as silicates as its major constituents. This satellite''s dense atmosphere of nitrogen with methane is unique. Deposits or even oceans of organic compounds have been suggested to exist on Titan''s solid surface due to UV-induced photochemistry in the atmosphere. Thus, the composition of the surface is a major piece of evidence needed to determine Titan''s history. However, studies of the surface are hindered by the thick, absorbing, hazy and in some places cloudy atmosphere. Ground-based telescope investigations of the integral disk of Titan attempted to observe the surface albedo in spectral windows between methane absorptions by calculating and removing the haze effects. Their results were reported to be consistent with water ice on the surface that is contaminated with a small amount of dark material, perhaps organic material like tholin. We analyze here the recent Cassini Mission''s visual and infrared mapping spectrometer (VIMS) observations that resolve regions on Titan. VIMS is able to see surface features and shows that there are spectral and therefore likely compositional units. By several methods, spectral albedo estimates within methane absorption windows between 0.75 and 5μm were obtained for different surface units using VIMS image cubes from the Cassini-Huygens Titan Ta encounter. Of the spots studied, there appears to be two compositional classes present that are associated with the lower albedo and the higher albedo materials, with some variety among the brighter regions. These were compared with spectra of several different candidate materials. Our results show that the spectrum of water ice contaminated with a darker material matches the reflectance of the lower albedo Titan regions if the spectral slope from 2.71 to 2.79μm in the poorly understood 2.8-μm methane window is ignored. The spectra for brighter regions are not matched by the spectrum of water ice or unoxidized tholin, in pure form or in mixtures with sufficient ice or tholin present to allow the water ice or tholin spectral features to be discerned. We find that the 2.8-μm methane absorption window is complex and seems to consist of two weak subwindows at 2.7 and 2.8μm that have unknown opacities. A ratio image at these two wavelengths reveals an anomalous region on Titan that has a reflectance unlike any material so far identified, but it is unclear how much the reflectances in these two subwindows pertain to the surface. [Copyright &y& Elsevier]