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1. The Cassini Visual and Infrared Mapping Spectrometer (VIMS) Investigation

Author

Brown, R. H., Baines, K. H., Bellucci, G., Bibring, J.-P., Buratti, B. J., Capaccioni, F., Cerroni, P., Clark, R. N., Coradini, A., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., Matson, D. L., Mccord, T. B., Mennella, V., Miller, E., Nelson, R. M., Nicholson, P. D., Sicardy, B., Sotin, C., and Russell, Christopher T., editor

Published
2004
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2. The Spectral Nature of Titan's Major Geomorphological Units

Author

Solomonidou, A., Coustenis, A., Lopes, R.M.C., Malaska, M. J., Rodriguez, S., Altobelli, N., Drossart, P., Elachi, Charles, Schmitt, B., Janssen, Michael A., Wall, S., Sotin, C., Lawrence, K.J., Radebaugh, J., Stephan, Katrin, Brown, Robert H., LeMouelic, Stephane, Le Gall, Alice, Witasse, Olivier, and Matsoukas, C.

Subjects
Planetengeologie, VIMS, Cassini, Titan
Published
2018

3. Titan's Major Geomorphological Units: Their Spectral and Morphological Nature

Author

Solomonidou, A., Coustenis, A., Drossart, P., Brown, Robert H., Stephan, Katrin, Altobelli, N., Sotin, C., Lawrence, K.J., Le Mouelic, S., Rodriguez, S., Schmitt, B., Le Gall, Alice, Elachi, Charles, Lopes, R.M.C., Witasse, Olivier, Radebaugh, J., Wall, S., Malaska, M. J., Janssen, M., and Matsoukas, C.

Subjects
Planetengeologie, VIMS, Cassini, Titan
Published
2018

4. Changes on Titan’s surface

Author

Solomonidou, A., Lopes, R.M.C., Coustenis, A., Malaska, M. J., Sotin, C., Rodriguez, S., Janssen, M., Drossart, Pierre, Lawrence, K.J., Matsoukas, C., Hirtzig, M., Mouélic, S. Le, Jaumann, Ralf, Brown, Robert H., and Bratsolis, E.

Subjects
Planetengeologie, surface, Cassini, Titan
Published
2015

5. Cassini VIMS and RADAR investigation of Titan’s equatorial regions: a case for changes in surface properties

Author

Solomonidou, Anezina, Coustenis, A., Lopes, R.M.C., Rodriguez, S., Hirtzig, M., Malaska, M. J., Stephan, Katrin, Sotin, C., Drossart, P., Jaumann, R., Bratsolis, E., Mouélic, S. Le, Brown, Robert H., Henry, Florence, Jet Propulsion Laboratory, California Institute of Technology (JPL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Fondation La main à la pâte, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institute of Planetary Research, DLR, Rutherfordstrasse 2, D-12489 Berlin, Germany, National and Kapodistrian University of Athens (NKUA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, United States

Subjects
Planetengeologie, VIMS, Cassini, surface properties, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], Titan, RADAR
Abstract

International audience; The Cassini-Huygens instruments revealed that Titan, Saturn's largest moon, has - in many aspects - a complex, dynamic and Earth-like surface [1;2;3]. Understanding the distribution and interplay of geologic processes on Titan is important for constraining models of its interior, surface-atmosphere interactions, and climate evolution. Data from the remote sensing instruments have shown the presence of diverse terrains, suggesting exogenic and endogenic processes, whose composition remains largely unknown. Interpreting surface features further requires precise knowledge of the contribution by the dense intervening atmosphere, especially the troposphere, which can be recovered from near-IR data such as those collected by Cassini's Visual and Infrared Mapping Spectrometer (VIMS) collects in the so-called "methane windows". In order to simulate the atmospheric contribution and extract surface information, a statistical tool (PCA) and a radiative transfer code are applied on certain regions of interest (i.e. possibly geologically varying and suggested in some cases to be cryovolcanic and/or evaporitic in origin) [4;5;7]. We also analyze RADAR despeckled SAR images in terms of morphology [6]. For comparison, we also look at undifferentiated plains and dune fields regions that are not expected to change with time. We find that Tui Regio and Sotra Patera change with time becoming darker and brighter respectively in terms of surface albedo while the plains and the suggested evaporitic areas in the equatorial regions do not present any significant change [5]. The surface brightening of Sotra supports a possible internal rather than exogenic origin. The unchanged surface behavior of the plains supports a sedimentary origin rather than cryovolcanic. Preliminary results on the chemical composition of the changed regions with time are also presented. We therefore suggest that temporal variations of surface albedo (in chemical composition and/or morphology) exist for some areas on Titan, but that their origin may differ from one region to the other. Such a variety of geologic processes and their relationship to the methane cycle make Titan particularly significant in Solar System studies. References: [1] Lopes, R.M.C., et al.: JGR, 118, 416-435, 2013 [2] Solomonidou, A., et al.: PSS, 70, 77-104, 2013 [3] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [4] Solomonidou, A., et al.: JGR, 119, 1729-1747, 2014; [5] Solomonidou, A., et al.: Icarus, submitted, 2015; [6] Bratsolis, E., et al.: PSS, 61, 108-113, 2012; [7] Hirtzig, M., et al.: Icarus, 226, 470-486, 2013.

Published
2015

6. The spectral evolution of various Titan geomorphic surface types

Author

Solomonidou, A., Coustenis, A., Lopes, R.M.C., Rodriguez, S., Malaska, M. J., Drossart, Pierre, Sotin, C., Lawrence, K.J., Hirtzig, M., Mouélic, S. Le, Stephan, K., Jaumann, Ralf, Maltagliati, L., and Brown, Robert H.

Subjects
Planetengeologie, surface, Cassini, Titan
Published
2015

7. The Eye of Saturn's North Polar Vortex: Unexpected Cloud Structures Observed at High Spatial Resolution by Cassini/VIMS.

Author

Baines, K. H., Sromovsky, L. A., Fry, P. M., Momary, T. W., Brown, R. H., Buratti, B. J., Clark, R. N., Nicholson, P. D., and Sotin, C.

Abstract

Abstract: Near‐infrared spectral maps of Saturn's north polar vortex obtained at high spatial resolution provided by Cassini/Visual Infrared Mapping Spectrometer (VIMS) reveal localized ammonia clouds composed of unusually large particles exceeding 13 μm in radius, the largest cloud particles documented during the Cassini mission. Taken under near‐optimum direct polar lighting and viewing conditions within a month of the summer solstice, these small (~200 km in breadth) discrete clouds are located within the eye of the polar vortex, which otherwise is unusually clear of observable aerosols in reflected sunlight, with total 2‐μm opacity <0.04 versus >1.0 elsewhere on Saturn. The dichotomy of large‐particle condensate cloud features—indicative of convective upwelling—within a large (~ 2000‐km diameter) nearly aerosol‐free region of downwelling characteristic of the core of a polar vortex reveals surprising polar dynamics on Saturn. [ABSTRACT FROM AUTHOR]

Published
2018
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8. Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs.

Author

Turtle, E. P., Perry, J. E., Barbara, J. M., Del Genio, A. D., Rodriguez, S., Le Mouélic, S., Sotin, C., Lora, J. M., Faulk, S., Corlies, P., Kelland, J., MacKenzie, S. M., West, R. A., McEwen, A. S., Lunine, J. I., Pitesky, J., Ray, T. L., and Roy, M.

Abstract

Abstract: Cassini observations of Titan's weather patterns over >13 years, almost half a Saturnian year, provide insight into seasonal circulation patterns and the methane cycle. The Imaging Science Subsystem and the Visual and Infrared Mapping Spectrometer documented cloud locations, characteristics, morphologies, and behavior. Clouds were generally more prevalent in the summer hemisphere, but there were surprises in locations and timing of activity: Southern clouds were common at midlatitudes, northern clouds initially appeared much sooner than model predictions, and north polar summer convective systems did not appear before the mission ended. Differences from expectations constrain atmospheric circulation models, revealing factors that best match observations, including the roles of surface and subsurface reservoirs. The preference for clouds at mid‐northern latitudes rather than near the pole is consistent with models that include widespread polar near‐surface methane reservoirs in addition to the lakes and seas, suggesting a broader subsurface methane table is accessible to the atmosphere. [ABSTRACT FROM AUTHOR]

Published
2018
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9. Geological Evolution of Titan's Equatorial Regions: Possible Nature and Origin of the Dune Material.

Author

Brossier, J. F., Rodriguez, S., Cornet, T., Lucas, A., Radebaugh, J., Maltagliati, L., Le Mouélic, S., Solomonidou, A., Coustenis, A., Hirtzig, M., Jaumann, R., Stephan, K., and Sotin, C.

Abstract

Abstract: In 13 years, infrared observations from the Visual and Infrared Mapping Spectrometer onboard Cassini provided significant hints about the spectral and geological diversity of Titan's surface. The analysis of the infrared (IR) signature of spectral units enables constraining the surface composition, which is crucial for understanding possible interactions between Titan's interior, surface, and atmosphere. Here we investigate a selection of areas in the equatorial regions, imaged by Cassini's instruments, which exhibit an apparent transition from the Visual and Infrared Mapping Spectrometer IR‐bright to the IR‐blue and IR‐brown units (from false‐color composites using red: 1.57/1.27 μm, green: 2.01/1.27 μm, and blue: 1.27/1.08 μm). By applying an updated radiative transfer model, we extract the surface albedo of IR units identified in these regions. Then, we compare them with synthetic mixtures of two expected components on Titan's surface, namely, water ice and laboratory tholins. This allows us to reconnect the derived composition and grain size information to the geomorphology observed from Radio Detection and Ranging instrument (RADAR)/Synthetic Aperture Radar images. We interpret IR‐bright units as hills and plains coated by organic material and incised by fluvial networks. Erosion products are transported downstream to areas where IR‐blue units are seen near the IR‐bright units. These units, enriched in water ice, are most likely outwash plains hosting debris from fluvial erosion. Farther away from the IR‐bright units, the IR‐brown units are dominantly made of organics with varied grain sizes, ranging from dust‐ to sand‐sized particles that form the dune fields. The transition areas therefore exhibit trends in water ice content and grain size supported by geomorphological observations. [ABSTRACT FROM AUTHOR]

Published
2018
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10. Cassini/VIMS Data Analysis of Potentially Geologically Varying Regions on Titan

Author

Solomonidou, A., Hirtzig, M., Bratsolis, E., Bampasidis, G., Coustenis, A., Kyriakopoulos, K., Le Mouélic, S., Rodriguez, S., Jaumann, R., Stephan, K., Lopes, R.M.C., Drossart, P., Sotin, C., Brown, R.H., Seymour, K.S., Moussas, X., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
Cassini, Titan, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience

Published
2012

11. Dark and Bright Albedo Changes in the Wake of a Titan Rainstorm

Author

Barnes, Jason W., Buratti, B. J., Turtle, E. P., Bow, J., Dalba, P. A., Perry, J., Rodriguez, S., LeMouelic, S., Baines, K. H., Sotin, C., Lorenz, R. D., Malaska, M. J., McCord, T. B., Clark, R. N., Jaumann, R., Hayne, P. O., Nicholson, P. D., Soderblom, J. M., and Soderblom, L. A.

Subjects
Albedo, ISS, VIMS, Cassini, Titan
Published
2012

12. Enceladus: Correlation of Surface Particle Distribution and Geology

Author

Jaumann, R., Stephan, K., Brown, Robert H., Clark, R. N., Filacchione, G., Buratti, B.J., Nelson, R.M., Nicholson, P. D., Le Mouelic, S., Rodriguez, S., Hansen, G.B., Roatsch, Thomas, Capaccioni, F., and Sotin, C.

Subjects
Planetengeologie, Enceladus, Cassini, Saturn satellite
Abstract

The surface of Enceladus consists almost completely of water ice [1,2]. The band depths of water ice absorptions are sensitive to the size of particles [2,3,4] covering the surface. The Visual and Infrared Mapping Spectrometer [5] observed Enceladus with high spatial resolution during multiple Cassini fly-bys. Based on these data we measured the band depths of water ice absorptions over Enceladus' surface and mapped their distribution. The spatial resolution of VIMS is sufficient to distinguish three major geologic units: heavily cratered terrain, fractured and ridged terrain and complex tectonically deformed regions of troughs and ridges [6], which include the south pole region. Surface ages, as derived from the impact flux models of [7,8] indicate the cratered terrain being oldest while the Sulci the youngest unit [2,9]. From the distribution of particle sizes we can conclude that the largest particle diameters are those inside the tectonically deformed regions, with a decrease in size departing from the fractures. These occur not only at the south pole but also in older tectonic regions [2]. The basic correlation between particle diameter, geologic unit and age suggests the following relative stratigraphic sequence [2,10]: (1) Formation of a primary crust (heavily cratered terrain); (2) Mechanical weathering of the surface particles by microimpacts and sputtering during the last 4 billion years; (3) Tectonic disruption of the surface and deposition of new material with large particles. Although this newly deposited material has undergone mechanical weathering of the particles by microimpacts and sputtering, these particles are larger due to a shorter exposure time; (4) Recent deposition of larger particles in the south polar region. If the larger particles in the tectonically deformed regions have of the same cryovolcanic origin as at the south pole, the volcanic activity must have a temporal evolution. However, there are still different possibilities to explain this observation [2]: (1) The eruption zones may have moved from north to south. (2) Cryovolcanic eruptions might have occurred across the entire surface and later shrunk to a small zone at the south pole, which would be indicative of a probable decrease in internal heat transfer. (3) The intensity of cryovolcanic eruptions had a different temporal evolution at different locations with maximum activity in the south polar region.

Published
2012

13. Potentially active regions on Titan: New processing of Cassini/VIMS data

Author

Solomonidou, A., Hirtzig, M., Bratsolis, E., Bampasidis, G., Coustenis, A., Kyriakopoulos, K., Le Mouelic, S., Stephan, K., Jaumann, R., Drossart, P., Sotin, C., Seymour, K., and Moussas, X.

Subjects
Planetengeologie, Cassini, Titan
Abstract

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) obtained data of Titan's surface from flybys performed during the last seven years. In the 0.8-5.2 µm range, these spectro-imaging data showed that the surface consists of a multivariable geological terrain hosting complex geological processes. The data from the seven narrow methane spectral "windows" centered at 0.93, 1.08, 1.27, 1.59, 2.03, 2.8 and 5 µm provide some information on the lower atmospheric context and the surface parameters that we want to determine. Atmospheric scattering and absorption need to be clearly evaluated before we can extract the surface properties. We apply here a statistical method [1, 2] and a radiative transfer method [3, 1] on three potentially "active" regions on Titan, i.e. regions possibly subject to change over time (in brightness and/or in color etc) [4]: Tui Regio (20°S, 130°W) [5], a 1,500-km long flow-like figure, Hotei Regio (26°S, 78°W) [6], a 700-km wide volcanic-like terrain, and Sotra Facula (15°S, 42°W) [7], a 235-km in diameter area. With our method of Principal Component Analysis (PCA) we have managed to isolate specific regions of distinct and diverse chemical composition. We have tested this method on the previously studied Sinlap crater [8], delimitating compositional heterogeneous areas compatible with the published conclusions by Le Mouélic et al. (2008). Our follow-up method focuses on retrieving the surface albedo of the three areas and of the surrounding terrains with different spectral response by applying a radiative transfer (RT) code. We have used as input most of the Cassini HASI and DISR measurements, as well as new methane absorption coefficients [9], which are important to evaluate the atmospheric contribution and to allow us to better constrain the real surface alterations, by comparing the spectra of these regions. By superposing these results onto the PCA maps, we can correlate composition and morphology. As a test case, we used our RT code to verify the varying brightness of Hotei Regio reported by other investigators based on models lacking proper simulation of the atmospheric absorption [10]. Even though we have used exactly the same dataset, we did not detect any significant surface albedo variations over time; this led us to revise the definition of "active" regions: even if these regions have not visually changed over the course of the Cassini mission, the determination of the chemical composition and the correlation with the morphological structures [11] observed in these areas do not rule out that past and/or ongoing cryovolcanic processes are still a possible interpretation. [1] Solomonidou, A. et al. (2011). Potentially active regions on Titan: New processing of Cassini/VIMS data. In preparation. [2] Stephan, K. et al. (2008). Reduction of instrument-dependent noise in hyperspectral image data using the principal component analysis: Applications to Galileo NIMS data. Planetary and Space Science 56, 406-419. [3] Hirtzig, M. et al. (2011). Applications of a new methane linelist to Cassini/VIMS spectra of Titan in the 1.28-5.2 µm range . In preparation. [4] Wall, s. D. et al. (2009). Cassini RADAR images at Hotei Arcus and western Xanadu, Titan: Evidence for geologically recent cryovolcanic activity. Journal of Geophysical Research 36, L04203, [5] Barnes, J.W. et al. (2006). Cassini observations of flow-like features in western Tui Regio, Titan. Geophysical Research Letters 33, L16204. [6] Soderblom, L.A. et al. (2009). The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR. Icarus 204, 610-618. [7] Lopes, R.M.C. et al. (2010). Distribution and interplay of geologic processes on Titan from Cassini radar data. Icarus 205, 540-558. [8] Le Mouélic et al. (2008). Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data. Journal of Geophysical Research 113, E04003. [9] Campargue, A. et al. (2011). An empirical line list for methane at 80 K and 296 K in the 1.26-1.71 µm region for planetary investigations. Application to Titan. Icarus. Submitted. [10] Nelson, R. et al (2009). Saturn's Titan: Surface change, ammonia, and implications for atmospheric and tectonic activity. Icarus 199, 429-441. [11] Solomonidou, A. et al. (2011). Possible morphotectonic features on Titan and their origin. Planetary and Space Science. Submitted.

Published
2012

14. Cassini/VIMS Spectra and Time-Evolution of Precipitation-Associated Surface Brightenings on Titan

Author

Barnes, J.W., Buratti, B.J., Turtle, E.P., Bow, J., Dalba, P.A., Perry, J., Rodriguez, S., Lé Mouélic, S., Baines, K.H., Sotin, C., Lorenz, R.D., Malaska, M.J., McCord, T.B., Brown, R.H., Clark, R.N., Jaumann, R., Hayne, P., Nicholson, P.D., Soderblom, J.M., and Soderblom, L.A.

Subjects
Planetengeologie, surface, Cassini, Titan
Abstract

Large areas of Titan’s surface brightened at all wavelengths as seen from Cassini/VIMS for several months. The brightenings occurred after a large storm and rainfall event, and may relate to volatile refreezing due to evaporative cooling.

Published
2012

15. Singular regional brightening events on Titan as seen by Cassini/VIMS

Author

Rodriguez, S., Le Mouélic, Stéphane, Barnes, J. W., Hirtzig, M., Rannou, P., Sotin, C., Brown, R. H., Bow, J., Vixie, Graham, Cornet, T., Bourgeois, O., Narteau, C., Courrech du Pont, S., Griffith, C. A., Jaumann, Ralf, Stephan, K., Buratti, B.J., Clark, R. N., Baines, K. H., Nicholson, P. D., and Coustenis, A.

Subjects
Planetengeologie, Saturn, satellite, Cassini, Titan
Abstract

Titan, the largest satellite of Saturn, is the only satellite in the solar system with a dense atmosphere. The close and continuous observations of Titan by the Cassini spacecraft, in orbit around Saturn since July 2004, bring us evidences that Titan tropo-sphere and low stratosphere experience an exotic, but complete meteorological cycle similar to the Earth hy-drological cycle, with hydrocarbons evaporation, con-densation in clouds, and rainfall. Cassini monitoring campaigns also demonstrate that Titan’s cloud cover-age and climate vary with latitude. Titan’s tropics, with globally weak meteorological activity and widespread dune fields, seem to be slightly more arid than the poles, where extensive and numerous liquid reservoirs and sustained cloud activity were discovered. Only a few tropospheric clouds have been observed at Titan’s tropics during the southern summer [2-4]. As equinox was approaching (in August 2009), they oc-curred more frequently and appeared to grow in strength and size [5-7].

Published
2012

16. Detection of a specular reflection on Titan by Cassini-VIMS

Author

Stephan, K., Jaumann, R., Brown, Robert H., Soderblom, Jason M., Soderblom, L.A., Barnes, Jason W., Sotin, C., Griffith, C. A., Kirk, R.L., Baines, K. H., Buratti, B.J., Clark, R. N., Lytle, D. M., Nelson, R.M., and Nicholson, P. D.

Subjects
Planetengeologie, VIMS, Cassini, Titan
Published
2010

17. Mimas: Preliminary Evidence For Amorphous Water Ice From VIMS

Author

Cruikshank, Dale P., Marzo, G., Pinilla-Alonso, N., Roush, T. L., Mastrapa, R. M., Dalle Ore, C. M., Buratti, B. J., Stephan, Katrin, Brown, R.H., Baines, K. H., Clark, R. N., Nicholson, P.D., and Sotin, C.

Subjects
Planetengeologie, Mimas, VIMS, Cassini
Published
2010

18. Spectrally Dominant Aromatic Hydrocarbon Compounds on Titan

Author

Clark, R.N., Pearson, N., Brown, R. H., Cruikshank, D., Barnes, J. W., Jaumann, R., Soderblom, L. A., Rodriguez, S., Le Mouelic, S., Lunine, J., Sotin, C., Baines, K.H., Buratti, B. J., Nicholson, P. D., Nelson, R. M., and Stephan, K.

Subjects
Planetengeologie, Cassini, Titan
Published
2010

19. Cassini/VIMS Discovery of Organic Evaporite Deposits in Titan's Dry Lakebeds

Author

Barnes, Jason W., Bow, J., Schwartz, J., Brown, R. H., Soderblom, J. M., Hayes, A., Le Mouélic, S., Rodriguez, S., Sotin, C., Jaumann, R., Stephan, K., Soderblom, L. A., Clark, R. N., Buratti, B. J., Baines, K. H., and Nicholson, P. D.

Subjects
Planetengeologie, Cassini, Titan
Published
2010

23. Spatial and Spectral Filtering Strategies for Cassini VIMS Surface Images of Titan

Author

Mouélic S., Le, Sotin, C., Rodriguez, S., Tobie, G., Corre L., Le, R. H., Brown, Barnes, J.W., Buratti, B., Soderblom, L., Jaumann, R., K. H., Baines, Clark, R., P. D., Nicholson, Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Planetengeologie, spectral channel, [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, VIMS, atmospheric transmission windows, Cassini, ComputingMethodologies_GENERAL, Titan, ComputingMilieux_MISCELLANEOUS
Abstract

The VIMS imaging spectrometer onbord CASSINI provides hyperspectral images of Titan in 352 spectral channels from 0.3 to 5.1 μm. In-frared channels are particularly useful to map the sur-face of Titan through narrow atmospheric transmission windows [1,2]. VIMS can be used for geomorphologi-cal studies thanks to the imaging capabilities. The spectral dimension is used to investigate the composi-tion of the surface materials. We focus here on the improvement of the S/N ratio both for surface imaging and spectral studies.

Published
2007

24. Saturn's Titan: Cassini VIMS reports regional reflectance change consistent with surface activity

Author

Nelson, R.M., Kamp, L., Matson, D.L., Irwin, P.G.J., Baines, K.H., Boryta, M.D., Leader, F.E., Jaumann, R., Smythe, W.D., Sotin, C., Clark, R.N., Cruikshank, D.P., Drossart, P., Pearl, J.C., Hapke, B.W., Lunine, J., Combes, M., Bellucci, G., Bibring, J.-P., Capaccioni, F., Cerroni, P., Coradini, A., Formisano, V., Filacchione, G., Langevin, R.Y., McCord, T.B., Mennella, V., Nicholson, P.D., and Sicardy, B.

Subjects
Planetengeologie, Saturn, brightenings, near-infrared reflectance, VIMS, Cassini, Titan
Abstract

The near-infrared reflectance of a 73,000 km2 area on Titan changed between July 2004 and March of 2006. The reflectance of the region (latitude 26S, longitude 78W) increased twofold between July 2004 and March-April 2005. It then returned to the July 2004 level by November 2005. By late December 2005 the reflectance had surged upward again to a new maximum. It then declined for the next three months. Detailed analyses indicate that the brightenings are a surface phenomenon, making these the first changes seen on Titan’s surface. The spectral differences between the region and its surroundings rule out the ices of H2O, CO2, and CH4 as possible causes. Remarkably, the change is spectrally consistent with the deposition and removal of ammoniated materials. NH3 has been proposed as a constituent of Titan’s interior but not its surface or atmosphere. This transitory NH3 spectral signature is consistent with occasional effusion events in which juvenile ammonia is brought to the surface. Its decomposition may feed nitrogen to the atmosphere. The size of the region suggests it may exceed the size of the largest active volcanic areas in the solar system.

Published
2007

26. Cassini/VIMS observations of Titan during the T20 flyby

Author

Sotin, C., LeMouelic, S., Brown, R.H., Barnes, J., Soderblom, L., Jaumann, R., Buratti, B.J., Clark, R.N., Baines, K.H., Nelson, R.M., Nicholson, P.D., and VIMS Science Team

Subjects
Planetengeologie, T20 Flyby, methane, infrared, VIMS, Cassini
Abstract

Since its insertion in Saturn’s environment in July 2004, the Cassini spacecraft has realized 20 Titan flybys. Three instruments can see through the haze: the ISS camera thanks to the infrared channel, the SAR (Synthetic Aperture Radar) and the Visual and Infrared Mapping Spectrometer (VIMS) [1]. During the first flyby, the VIMS showed its great potential to map and to characterize Titan’s surface despite scattering by haze particles and strong absorption of light by methane contained in the atmosphere [2]. Six infrared windows provide images of Titan’s surface and its spectral properties. At closest approach, the spatial resolution can be as good as 250 m/pixel, a resolution similar to that of the radar swaths. Because the VIMS capabilities were unexpected before the first observations, the VIMS had never been the prime instrument at closest approach before the T20 flyby that happened on 24 October 2006. This paper reports on the findings of this flyby.

Published
2007

27. Surface erosion of Titan

Author

Jaumann, R., Brown, R.H., Stephan, K., Soderblom, L.A., Sotin, C., Le Mouélic, S., Rodriguez, S., Clark, R.N., Barnes, J., Buratti, B.J., McCord, T.B., Baines, K.H., Cruikshank, D.P., Griffith, C.A., and Nicholson, P.D.

Subjects
Planetengeologie, dune fields, Huygens, VIMS, Cassini, sand seas, Titan, T20, Surface erosion
Abstract

The surface of Titan has been revealed globally by the Cassini observations in the infrared and radar wavelength ranges as well as locally by the Huygens instruments. Sand seas, recently discovered lakes, distinct landscapes and dendritic erosion pattern indicate dynamic surface processes. During Cassini’s T20 flyby the Visible and Infrared Mapping Spectrometer (VIMS) [1] observed an extremely eroded area at 30° W, 7° S with resolution better than 350 m. Analyses of the drainage dynamics and comparison with the drainage systems at the Huygens landing site yield high discharge values of the associated channel systems and extreme runoff production rates of 10 to 50 cm/day. In addition, large sandur-like alluvial fans covering ten thousands of square kilometres are discovered at the boundary between high-standing bright and low-laying dark regions. To account for the estimated runoff production and widespread alluvial fan deposits of fine-grained material both frequent recurrence intervals and sudden release of areadependent large fluid volumes are required. Frequent equatorial storms with heavy rainfall of methane and related hydrocarbons might explain this catastrophic erosion. High-energy flow will cause mechanical weathering and large accumulations of sand in alluvial fans that is picked up by winds to form Titan’s vast equatorial sand seas and dune fields.

Published
2007

28. Nearinfrared spectral mapping of Titan's mountains and channels

Author

Barnes, J.W., Radebaugh, J., Brown, R.H., Wall, S., Soderblum, L., Lunine, J., Buratti, B.J., Baines, K.H., Sotin, C., Le Mouelic, S., Rodriguez, S., Clark, R.N., Nicholson, P.D., Jaumann, Ralf, Lopes, R., Mitchell, K., Lorenz, R., and Wood, C.A.

Subjects
Spectral Mapping, Institut für Planetenforschung, VIMS, Cassini, Titan, Mountain, Channel
Abstract

Cassini studies of the surface of Titan are beginning to reveal its nature. In addition to hills, channels, and cobbles seen by the Huygens probe, the Visual and Infrared Mapping Spectrometer (VIMS) and RADAR instruments onboard the orbiter have seen sand dunes , channels , mountains [5, 6], and cryovolcanic candidates. Recently the RADAR team announced the discovery of possible lakes near Titan’s north pole.

Published
2007

29. Determination of the Haze Layer Parameters in the Saturn Atmosphere from Cassini-VIMS Images

Author

Adriani, A., Moriconi, M., Colosimo, F., Coradini, A., Filacchione, G., Orosei, R., D Aversa, E., Capaccioni, F., Cerroni, P., Bellucci, G., Brown, R. H., Baines, K. H., Bibring, J. -P, Buratti, B. J., Clark, R. N., Combes, M., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., Matson, D. L., Mccord, T. B., Vito Mennella, Nelson, R. M., Nicholson, P. D., Sicardy, B., Sotin, C., Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
Planetengeologie, Saturn, Atmosphere, Haze layers, VIMS, Cassini, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2006

30. Consideration on the Titan topography based on the Cassini-VIMS measurements in the NIR range

Author

Moriconi, M., Adriani, A., Gardini, A., Coradini, A., Filacchione, G., Orosei, R., D'Aversa, E., Capaccioni, F., Cerroni, P., Bellucci, G., Brown, R. H., Baines, K. H., Bibring, J. P., Buratti, B. J., Clark, R. N., Combes, M., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., Matson, D. L., McCord, T. B., Mennella, V., Nelson, R. M., Nicholson, P. D., Sicardy, B., and Sotin, C.

Subjects
Planetengeologie, topography, Saturnian system, VIMS, Cassini, NIR, Titan
Published
2006

31. Distribution of icy particles across Enceladus' surface

Author

Jaumann, R., Stephan, K., Wagner, R., G. B., Hansen, R. H., Brown, K. H., Baines, Belucci, G., J.-P., Bibring, B. J., Buratti, Capaccioni, F., Cerroni, P., R. N., Clark, Combes, M., Coradini, A., D. P., Cruikshank, Drossart, P., Filacchione, G., Formisano, V., C. A., Hibbitts, Langevin, Y., D. L., Matson, T. B., Mccord, Menella, V., R. M., Nelson, P. D., Nicholson, Sicardy, B., Sotin, C., Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
Planetengeologie, Enceladus, [SDU]Sciences of the Universe [physics], Saturnian Moons, ice, VIMS, Cassini, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2006

32. Cassini/VIMS observations of Titan: geological implications

Author

Sotin, C., Rodriguez, S., Le Mouélic, S., Tobie, G., Buratti, B. J., Brown, R. H., Jaumann, R., Clark, R. N., Baines, K. H., McCord, T. B., Nelson, R. M., and VIMS Science Team

Subjects
Planetengeologie, geology, VIMS, Cassini, Titan
Published
2006

33. Cassini observations of the opposition effect of Saturn's rings 1

Author

Nelson, R. M., Hapke, B. W., Brown, R. H., Spilker, L. J., Smythe, W. D., Kamp, L., Boryta, M., Leader, F., Matson, D. L., Edgington, S., Nicholson, P. D., Filacchione, G., Clark, R. N., Bibring, J.-P., Baines, K. H., Buratti, B., Bellucci, G., Capaccioni, F., Cerroni, P., Combes, M., Coradini, A., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., McCord, T. B., Mennella, V., Sicardy, B., and Sotin, C.

Subjects
Planetengeologie, Saturn, VIMS, Cassini, opposition effect, rings
Published
2006

34. Titan: surface composition from Cassini VIMS

Author

McCord, T. B., Hansen, G. B., Buratti, B. J., Clark, R. N., Cruikshank, D. P., D'Aversa, E., Griffith, C. A., Baines, K. H., Brown, R. H., Dalle Ore, C. M., Filacchione, G., Formisano, V., Hibbitts, C. A., Jaumann, R., Lunine, J. I., Nelson, R. M., Sotin, C., and Cassini VIMS Team

Subjects
Planetengeologie, Saturnian system, surface composition, VIMS, Cassini, Titan
Published
2006

35. Iapetus, Phoebe and Hyperion: are they related?

Author

Tosi, F., Coradini, A., Capaccioni, F., Cerroni, P., Filacchione, G., Bellucci, G., Adriani, A., Moriconi, M., D Aversa, E., Brown, R. H., Baines, K. H., Bibring, J. -P, Buratti, B. J., Clark, R. N., Combes, M., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., Matson, D. L., Mccord, T. B., Vito Mennella, Nelson, R. M., Nicholson, P. D., Sicardy, B., Sotin, C., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Planetengeologie, Phoebe, [SDU]Sciences of the Universe [physics], Iapetus, Saturnian moons, VIMS, Cassini, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS, Hyperion
Abstract

International audience

Published
2006

36. Cassini VIMS Preliminary Exploration of Titan's Surface Hemispheric Albedo Dichotomy

Author

Nelson, R. M., Brown, R. H., Hapke, B. W., Smythe, W. D., Kamp, L., Boryta, M., Baines, K. H., Bellucci, G., Biebring, J. P., Buratti, B. J., Capaccioni, F., Cerroni, P., Clark, R. N., Coradini, A., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., Matson, D. L., Mccord, T. B., Vito Mennella, Nicholson, P. D., Sicardy, B., Sotin, C., Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
Institut für Planetenforschung, albedo dichotomy, VIMS, Cassini, Saturnian satellites, Titan, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2005

37. Cassini VIMS at Saturn: The first 6 months

Author

Brown, R. H., Baines, K. H., Bellucci, G., Buratti, B. J., Capaccioni, F., Cerroni, P., Clark, R. N., Coradini, A., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Matson, D. L., Mccord, T. B., Vito Mennella, Nelson, R. M., Nicolson, P., Sicardy, B., Sotin, C., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)

Subjects
Saturn, Institut für Planetenforschung, VIMS, Saturnian Satellites, Cassini, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience

Published
2005

38. The history and processes of Titan's equator from the geospatial-topology of spectrally distinct units.

Author

Kutsop, N., Hayes, A.G., Sotin, C., Lunine, J.I., Birch, S.P.D., Corlies, P.M., Lawrence, K., Le Mouélic, S., Madden, J., Malaska, M.J., Rodriguez, S., Soderblom, J.M., and Solomonidou, A.

Subjects
*MONTE Carlo method, *VECTOR quantization, *IR spectrometers, *GEOMORPHOLOGY
Abstract

We use hyperspectral-imaging observations from the Visual and Infrared Mapping Spectrometer (VIMS) to identify and explain processes of Titan's equator through the qualitative spatial relationships between geographic features (i.e. geospatial-topology). Our geographic features are defined by their spectra and geomorphology. We use tens of millions of VIMS pixels between 30°S and 30°N with incidence and emission angles <75°, and a pixel spatial scale of 200 km or less. Our dataset is several orders of magnitude larger than previous studies. This is possible through our use of novel techniques to reduce scattering and improve inter-flyby comparisons. We validate the dataset produced by these techniques by reproducing the results of previous studies. We use vector quantization, dimension reduction, and the Monte Carlo method to identify 14–16 spectrally and spatially distinct units within our dataset, a priori maps or images. These spectral units occur in distinct sequences, indicating that there is a discrete number of spectral pathways to describe the transitions across the surface. Using the same methodology used to identify the spectral units, we determine the spectral transition between units can be explained by five spectroclines. We define a spectrocline as the geographic expression of change in spectra between two spectrally distinct units; it is the spectral equivalent of an ecocline. We compare the spectra of the five spectroclines to the USGS spectral library to identify candidates for the change in compositions across the equator. We find evidence among the spectra of the spectroclines for changes in abundance of water-ice, acetylene, benzene, and alkane species. With the help of the geomorphological units identified in Cassini RADAR images, we discuss the significance of the spectral units and the spectroclines based on their geospatial-topology including their distribution, frequency, size, patterns, and sequences. From the correlations we identify between the spectra and geomorphology, we propose mechanisms for the formation and evolution of Titan's equatorial surface features. •.At Titan's equator, variance in the spectra can be explained by 14–16 units and in the spectral gradient by 5 spectroclines. • Compositional candidatesfor changing spectra are identified including water-ice, acetylene, benzene, and alkanes. • Hummock rich plains, like Xanadu, show evidence of being more organic rich than the undifferentiated plains on the surface. • Windward vs. leeward spectral topology shows aeolian transport effects on equatorial evolution. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Cassini Observations of the Opposition Effect of Saturn's Rings 2. Interpretation: Plaster of Paris as an Analog of Ring Particles

Author

Hapke, B. W., Nelson, R. M., Brown, R. H., Spilker, L. J., Smythe, W. D., Kamp, L., Boryta, M. C., Leader, F., Matson, D. L., Edgington, S., Nicholson, P. D., Filacchione, G., Clark, R. N., Bibring, J. -P, Baines, K. H., Buratti, B. J., Bellucci, G., Capaccioni, F., Cerroni, P., Combes, M., Coradini, A., Cruikshank, D. P., Drossart, P., Formisano, V., Jaumann, R., Langevin, Y., Mccord, T. B., Vito Mennella, Sicardy, B., Sotin, C., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), and Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Planetengeologie, Saturn, VIMS, Cassini, opposition effect, rings, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

40. Titan's fluvial valleys: Morphology, distribution, and spectral properties

Author

Langhans, M.H., Jaumann, R., Stephan, K., Brown, R.H., Buratti, B.J., Clark, R.N., Baines, K.H., Nicholson, P.D., Lorenz, R.D., Soderblom, L.A., Soderblom, J.M., Sotin, C., Barnes, J.W., and Nelson, R.

Subjects
*SYNTHETIC aperture radar, *FLUVIAL geomorphology, *METEOROLOGICAL precipitation, *CLIMATE change, *DIVERGENCE (Meteorology), *TITAN (Satellite), TITANIAN atmosphere
Abstract

Abstract: Titan''s fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on Titan on a global scale. It will also study the spatial relations between fluvial valleys and Titan''s geologic units and spectral surface units which have become accessible thanks to Cassini-VIMS data. Several distinct morphologic types of fluvial valleys can be discerned by SAR-images. Dendritic valley networks appear to have much in common with terrestrial dendritic systems owing to a hierarchical and tree-shaped arrangement of the tributaries which is indicative of an origin from precipitation. Dry valleys constitute another class of valleys resembling terrestrial wadis, an indication of episodic and strong flow events. Other valley types, such as putative canyons, cannot be correlated with rainfall based on their morphology alone, since it cannot be ruled out that they may have originated from volcanic/tectonic action or groundwater sapping. Highly developed and complex fluvial networks with channel lengths of up to 1200km and widths of up to 10km are concentrated only at a few locations whereas single valleys are scattered over all latitudes. Fluvial valleys are frequently found in mountainous areas. Some terrains, such as equatorial dune fields and undifferentiated plains at mid-latitudes, are almost entirely free of valleys. Spectrally, fluvial terrains are often characterized by a high reflectance in each of Titan''s atmospheric windows, as most of them are located on Titan''s bright ‘continents’. Nevertheless, valleys are spatially associated with a surface unit appearing blue due to its higher reflection at in a VIMS false color RGB composite with R: , G: , and B: ; the channels either dissect pure bluish surface units or they are carved into terrain with a mixed spectral signature between bright and bluish surface materials. The global picture of fluvial flows clearly indicates a high diversity of parameters controlling fluvial erosion, such as climatic processes, as well as surface and bedrock types. Recent fluvial activity is very likely in the north polar region in contrast to more arid conditions at lower latitudes and at the south pole of Titan. This divergence is probably an indication of seasonal climatic asymmetries between the hemispheres. However, traces of previous fluvial activity are scattered over all latitudes of Titan, which is indicative of previous climatic conditions with at least episodic rainfall. [Copyright &y& Elsevier]

Published
2012
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41. Composition of Titan's surface from Cassini VIMS

Author

McCord, T.B., Hansen, G.B., Buratti, B.J., Clark, R.N., Cruikshank, D.P., D’Aversa, E., Griffith, C.A., Baines, E.K.H., Brown, R.H., Dalle Ore, C.M., Filacchione, G., Formisano, V., Hibbitts, C.A., Jaumann, R., Lunine, J.I., Nelson, R.M., and Sotin, C.

Subjects
*ALBEDO, *ASTROPHYSICAL radiation, *TITAN (Satellite), *SPECTRUM analysis
Abstract

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]

Published
2006
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42. Photometrically-corrected global infrared mosaics of Enceladus: New implications for its spectral diversity and geological activity.

Author

Robidel, R., Le Mouélic, S., Tobie, G., Massé, M., Seignovert, B., Sotin, C., and Rodriguez, S.

Subjects
*IR spectrometers, *INFRARED spectra, *ORDERED sets, *GEOLOGIC hot spots, *WAVELENGTHS, *TIGERS, *GEODIVERSITY, WESTERN countries
Abstract

Between 2004 and 2017, spectral observations have been gathered by the Visual and Infrared Mapping Spectrometer (VIMS) on-board Cassini (Brown et al., 2004) during 23 Enceladus close encounters, in addition to more distant surveys. The objective of the present study is to produce a global hyperspectral mosaic of the complete VIMS data set of Enceladus in order to highlight spectral variations among the different geological units. This requires the selection of the best observations in terms of spatial resolution and illumination conditions. We have carried out a detailed investigation of the photometric behavior at several key wavelengths (1.35, 1.5, 1.65, 1.8, 2.0, 2.25, 2.55 and 3.6 μm), characteristics of the infrared spectra of water ice. We propose a new photometric function, based on the model of Shkuratov et al. (2011). When combined, corrected mosaics at different wavelengths reveal heterogeneous areas, in particular in the terrains surrounding the Tiger Stripes on the South Pole and in the northern hemisphere around 30°N, 90°W. Those areas appear mainly correlated to tectonized units, indicating an endogenous origin, potentially driven by seafloor hotspots. [ABSTRACT FROM AUTHOR]

Published
2020
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