CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Secondary Papers
2014
Porco, C., DiNino, D., Nimmo, F. (2014). "How the Geysers, Tidal Stresses, and Thermal Emissions Across the South Polar Terrain of Enceladus Are Related" The Astronomical Journal 148:45.


Nimmo, F., Porco, C., Mitchell, C. (2014). "Tidally Modulated Eruptions On Enceladus: Cassini ISS Observations and Models" The Astronomical Journal 148:46.


McKay, C., Anbar, A., Porco, C.,Tsou, P. (2014). "Follow the Plume: The Habitability of Enceladus" Astrobiology 14, 352-355.




2013
Attree, N., Murray, C., Williams, G., Cooper, N. (2013). "Survey of low-velocity collisional features in Saturn's F ring" Icarus 277, 56-66.


Thomas, P., Burns, J., Hedman, M., Helfenstein, P., Morrison, S., Tiscareno, M., Veverka, J. (2013). "The inner small satellites of Saturn: A variety of worlds" Icarus 226, 99-1019.


Tiscareno, M., Hedman, M., Burns, J., Weiss, J., Porco, C. (2013). "Probing the inner boundaries of Saturn's A ring with the Iapetus -1:0 nodal bending wave" Icarus 224, 221.


Cooper, N., Murray, C., Williams, G. (2013). "Local Variability in the Orbit of Saturn's F ring" The Astronomical Journal 145, 161-175.


Tiscareno, M., Mitchell, C., Murray, C., Di Nino, D., Hedman, M., Schmidt, J., Burns, J., Cuzzi, J., Porco, C., Beurle, K., Evans, M. (2013). "Observations of ejecta clouds produced by impacts onto Saturn's rings" Science 340, 460.


Tiscareno, M. (2013). "Planetary Rings" Planets, Stars and Stellar Systems, Volume 3: Solar and Stellar Planetary Systems 3, 309-376.


Roatsch, T., Kersten, E., Hoffmeister, A., Wahlisch, M., Matz, K.-D., Porco, C. (2013). "Recent improvements of the Saturnian Satellites Atlases: Mimas, Enceladus, and Dione" Planetary and Space Sciences 77, 118-125.


Tajeddine, R., Cooper, N.J., Lainey, V., Charnoz, S., Murray, C.D. (2013). "Astrometric Reduction of Cassini ISS Images of the Saturnian Satellites Mimas and Enceladus" Astronomy & Astrophysics 551, A129-A139.




2012
West, R.A., Ajello, J.M., Stevens, M.H., Strobel, D.F., Gladstone, G.R., Evans, J.S., Bradley, E.T. (2012). "Titan airglow during eclipse" Geophysical Research Letters 39, L18204.


Attree, N.O, Murray, C.D., Cooper, N.J., Williams, G.A. (2012). "Detection of low-velocity collisions in Saturn's F ring" The Astrophysical Journal Letters 755, L27-L31.


Del Genio, A.D., Barbara, J.M. (2012). " Constraints on Saturn's tropospheric general circulation from Cassini ISS images" Icarus 219, 689-700.


Roatsch, Th., Kersten, E., Wahlisch, M., Hoffmeister, A., Matz, K.-D., Scholten, F., Wagner, R., Denk, T., Neukum, G., and Porco, C. C. (2012). "High-resolution atlas of Rhea derived from Cassini-ISS images" Planetary Space Sciences 61, 135-141.


Hedman, M.M, Burns, J.A., Hamilton, D.P., Showalter, M.R. (2012). "The three-dimensional structure of Saturn's E ring" Icarus 217, 322-338.




2011
Fischer, G., Kurth, W.S., Gurnett, D.A., Zarka, P., Dyudina, U.A., Ingersoll, A.P., Ewald, S.P., Porco, C., Wesley, A. Go, C., Delcroix, M. (2011). "A giant thunderstorm on Saturn" Nature 475, 75-77.


West, R.A., Balloch, J., Dumont, P., Lavvas, P., Lorenz, R., Rannou, P., Ray, T., Turtle, E.P. (2011). "The evolution of Titan's detached haze layer near equinox in 2009" Geophysical Research Letters 38, L06204.


Hedman, M.M., Burns, J.A., Evans, M.W., Tiscareno, M.S., Porco, C.C. (2011). "Saturn's Curiously Corrugated C Ring" Science 332, 708-711 .


Turtle, E.P., Perry, J., Hayes, A., Lorenz, R., Barnes, J., McEwen, A., West, R,. Del Genio, A., Barbara, J., Lunine, J., Schaller, E., Ray, T., Lopes, R., Stofan, E. (2011). "Rapid and extensive surface changes near Titan's equator: Evidence of April showers" Science 331, 1414-1417.


Turtle, E.P., Perry, J.E., Hayes, A.G., McEwen, A.S. (2011). "Shoreline retreat at Titan's Ontario Lacus and Arrakis Planitia from Cassini Imaging Science Subsystem observations" Icarus 212, 957-959.


Turtle E.P., Del Genio A.D., Barbara J., Perry J.E., Schaller E., McEwen A.S., West R.A., Ray T.L. (2011). "Seasonal changes in Titan's meteorology" Geophysical Research Letters 38, L03203.




2010
Morales-Juberias, R., Sayanagi, K.M., Dowling, T.E., Ingersoll, A.P. (2010). "Emergence of Polar-jet Polygons from Jet Instabilities in a Saturn Model" Icarus 211, 1284-1293.


Spitale, J.N., Porco, C.C. (2010). "Free Unstable Modes and Massive Bodies in Saturn's Outer B Ring" Astronomical Journal 140, 1747-1757.


Hayes A.G., Aharonson O., Lunine J.I., Kirk R.L., Zebker H.A., Wye L.C., Lorenz R.D., Turtle E.P., Paillou P., Mitri G., Wall S.D., Stofan E.R., Mitchell K.L., Elachi C., and the Cassini RADAR team (2010). "Transient surface liquid in Titan's polar regions from Cassini" Icarus 211, 655-671.


Sayanagi, K.M., Morales-Juberias, R. and Ingersoll, A.P. (2010). "Saturn's Northern Hemisphere Ribbon: Simulations and Comparison with the Meandering Gulf Stream" Journal of the Atmospheric Sciences 67, 2658-2678.


Tiscareno, M.S., Burns, J.A., Cuzzi, J.N., Hedman, M.W. (2010). "Cassini imaging search rules out rings around Rhea" Geophysical Research Letters 37, L14205.


West, R., Knowles, B., Birath, E., Charnoz, S., DiNino, D., Hedman, M., Helfenstein, P., McEwen, A., Perry, J., Porco, C., Salmon, J., Throop, H., Wilson, D. (2010). "In-flight Calibration of the Cassini Imaging Science Sub-system Cameras" Planetary and Space Science 58, 1475-1488.


Beurle, K., Murray, C. D., Williams, G. A., Evans, M. W., Cooper, N. J., Agnor, C. B. (2010). "Direct Evidence for Gravitational Instability and Moonlet Formation in Saturn's Rings" Astrophysical Journal Letters 718, L176-L180.


Tiscareno, M.S., Burns, J.A., Sremcevic, M., Beurle, K., Hedman, M.M., Cooper, N.J., Milano, A.J., Evans, M.W., Porco, C.C., Spitale, J.N. Weiss, J.W. (2010). "Physical Characteristics and Non-Keplerian Orbital Motion of "Propeller" Moons Embedded in Saturn's Rings" Astrophysical Journal Letters 718, L92-L96.


Hedman, M. M.; Burt, J. A.; Burns, J. A.; Tiscareno, M. S. (2010). "The shape and dynamics of a heliotropic dusty ringlet in the Cassini Division" Icarus 210, 284-297.


Dyudina, U. A., Ingersoll, A. P., Ewald, S. P., Porco, C. C., Fischer, G., Kurth, W. S., West, R. A. (2010). "Detection of Visible Lightning on Saturn" Geophysical Research Letters 37, L09205.


Hedman, M.M., Cooper, N.J., Murray, C.D., Beurle, K., Evans, M.W., Tiscareno, M.S., Burns, J.A. (2010). "Aegaeon (Saturn LIII), a G-ring Object" Icarus 207, 433-447.






Denk, T., Neukum, G., Roatsch, T., Porco, C.C., Burns, J.A., Galuba, G.G., Schmedemann, N., Helfenstein, P., Thomas, P.C., Wagner, R.J., West, R.A. (2010). "Iapetus: Unique Surface Properties and a Global Color Dichotomy from Cassini Imaging" Science 327, 435-439.


Gombosi, T.I., Ingersoll, A.P. (2010). "Saturn: Atmosphere, Ionosphere, and Magnetosphere" Science 327, 1476-1479.




2009
Tiscareno, M., Thomas, P. C., Burns, J.A. (2009). "The rotation of Janus and Epimetheus" Icarus 204, 254-261 .


Spitale, J.N., Porco, C.C. (2009). "Time Variability in the Outer Edge of Saturn's A-Ring Revealed by Cassini Imaging" Astronomical Journal 138, 1520-1528.


Hahn, J.M., Spitale, J.N., Porco, C.C. (2009). "Dynamics of the Sharp Edges of Broad Planetary Rings" Astrophysical Journal 699, 686-710.


Morrison, S.J., Thomas, P.C., Tiscareno, M.S., Burns, J.A., Veverka, J. (2009). "Grooves on Small Saturnian Satellites and Other Objects: Characteristics and Significance" Icarus 204, 262-270.


Weiss, J.W., Porco, C.C., Tiscareno, M.S. (2009). "Ring Edge Waves and the Masses of Nearby Satellites" Astronomical Journal 138, 272-286.


Roman, M.T., West, R.A., Banfield, D.J., Gierasch, P.J., Achterberg, R.K., Nixon, C.A., Thomas, P.C. (2009). "Determining a Tilt in Titan's North-South Albedo Asymmetry from Cassini Images" Icarus 203, 242-249.


Hedman, M.M, Burns, J.A., Tiscareno, M.S., Porco, C.C. (2009). "Organizing some very tenuous things: Resonant structures in Saturn's faint rings" Icarus 202, 260-279.


Dyudina, U.A., Ingersoll, A.P., Ewald, S.P., Vasavada, A.R., West, R.A., Baines, K.H., Momary, T.W., Del Genio, A.D., Barbara, J.M., Porco, C.C., Achterberg, R.K., Flasar, F.M., Simon-Miller, A.A., Fletcher, L.N. (2009). "Saturn's south polar vortex compared to other large vortices in the Solar System" Icarus 202, 240-248.


Turtle, E. P., Perry, J. E., McEwen, A. S., DelGenio, A. D., Barbara, J., West, R. A., Dawson, D. D., Porco, C. C. (2009). "Cassini imaging of Titan's high-latitude lakes, clouds, and south-polar surface changes" Geophysical Research Letters 36, L02204.


Roatsch, T., Wählisch, M., Hoffmeister, A., Kerston, E., Matz, K.D., Scholten, F., Wagner, R., Denk, T., Neukum, G., Helfenstein, P., Porco, C. (2009). "High Resolution Atlases of Mimas, Tethys, and Iapetus derived from Cassini-ISS images" Planetary and Space Sciences 57, 83-92.


Hedman, M.M., Murray, C.D., Cooper, N.J., Tiscareno, M.S., Beurle, K., Evans, M.W., Burns, J.A. (2009). "Three Tenuous Rings/Arcs for Three Tiny Moons" Icarus 199, 378-386.


Dones, L., Chapman, C. R., McKinnon, W. B., Melosh, H. J., Kirchoff, M. R., Neukum, G., Zahnle, K. J. (2009). "Icy Satellites of Saturn: Impact Cratering and Age Determination," Saturn From Cassini-Huygens, M. Dougherty, L. Esposito, S. Krimigis, Eds. (Springer-Verlag, Dordrecht, Netherlands), pp. 613-635. ISBN 978-1-4020-9216-9.


Del Genio, A.D., Achterberg, R.K., Baines, K.H., Flasar, F.M., Read, P.L., Sanchez-Lavega, A., Showman, A.P. (2009). "Saturn Atmospheric Structure and Dynamics" Saturn From Cassini-Huygens, M. Dougherty, L. Esposito, S. Krimigis, Eds. (Springer-Verlag, Dordrecht, Netherlands), pp. 113-159. ISBN 978-1-4020-9216-9.


Roatsch, Th., Jaumann, R., Stephan, K.,Thomas, P.C. (2009). "Cartographic Mapping of the Icy Satellites Using ISS and VIMS Data" Saturn From Cassini-Huygens, M. Dougherty, L. Esposito, S. Krimigis, Eds. (Springer-Verlag, Dordrecht, Netherlands), pp. 763-781. ISBN 978-1-4020-9216-9.


West, R. A., Baines, K. H., Karkoschka, E., Sanchez-Lavega, A. (2009). "Clouds and Aerosols in Saturn's Atmosphere" Saturn From Cassini-Huygens, M. Dougherty, L. Esposito, S. Krimigis, Eds. (Springer-Verlag, Dordrecht, Netherlands), pp. 161-179. ISBN 978-1-4020-9216-9.


Tomasko, M.G., West, R.A. (2009). "Aerosols in Titan's Atmosphere" Titan from Cassini-Huygens, Brown, R., Lebreton, J.P., Waite, H., Eds. (Springer-Verlag, Dordrecht, Netherlands), pp. 297-322. ISBN 978-1-4020-9214-5.


Flasar, F. M., Baines, K. H., Bird, M. K., Tokano, T., West, R. A. (2009). "Atmospheric Dynamics and Meteorology" Titan from Cassini-Huygens, Brown, R., Lebreton, J.P., Waite, H., Eds. (Springer-Verlag, Dordrecht, Netherlands), pp. 323-353. ISBN 978-1-4020-9214-5.


Ingersoll, A.P., Pankine, A.A. (2009). "Subsurface Heat Transfer on Enceladus: Conditions under Which Melting Occurs" Icarus 206, 594-607.




2008
Giese, B., Wagner, R., Hussmann, H., Neukum, G., Perry, J., Helfenstein, P., and Thomas, P. C. (2008). "Enceladus: An Estimate of Heat Flux and Lithospheric Thickness from Flexurally Supported Topography" Geophysical Research Letters 35, L24204.


Porco, C. (2008). "The Restless World of Enceladus" Scientific American 299, No. 6, 52-63.


Porco, C., Weiss, J., Richardson, D., Dones, L., Quinn, T., Throop, H. (2008). "Simulations of the Dynamical and Light-Scattering Behavior of Saturn's Rings and the Derivation of Ring Particle and Disk Properties" Astronomical Journal 136, 2172-2200.


Roatsch, T., Wählisch, M., Hoffmeister, A., Matz, K.-D., Scholten, F., Kersten, E., Wagner, R., Denk, T., Neukum, G., Porco, C. (2008). "High Resolution Dione Atlas derived from Cassini-ISS images" Planetary and Space Sciences 56, 1499-1505.


Murray, C.D., Beurle, K., Cooper, N.J., Evans, M.W., Williams, G.A., Charnoz, S. (2008). "The determination of the structure of Saturn's F ring by nearby moonlets." Nature 453, 739-744.


Dyudina, U.A., Ingersoll, A.P., Ewald, S.P., Vasavada, A.R., West, R.A., Del Genio, A.D., Barbara, J.M., Porco, C.C., Achterberg, R.K., Flasar, F.M., Simon-Miller, A.A., Fletcher, L.N. (2008). "Dynamics of Saturn's South Polar Vortex." Science 319, 1801.


Tiscareno, M.S., Burns, J.A., Hedman, M.M., Porco, C.C. (2008). "The population of propellers in Saturn's A Ring." Astronomical Journal 135, 1083-1091.


Cooper, N.J., Murray, C.D., Evans, M.W., Beurle, K., Jacobson, R.A., Porco, C.C. (2008). "Astrometry and Dynamics of Anthe (S/2007 S 4), A New Satellite of Saturn." Icarus 195, 765-777.


Giese, B., Denk, T., Neukum, G., Roatsch, T., Helfenstein, P., Thomas, P.C., Turtle, E.P., McEwen, A., Porco, C.C. (2008). "The topography of Iapetus' leading side." Icarus 193, 359-371.


Jacobson, R., Spitale, J., Porco, C., Beurle, K., Cooper, N., Evans, M., Murray, C. (2008). "Revised Orbits of Saturn's Small Inner Satellites." Astronomical Journal 135, 261-263.


Roatsch, Th., Waehlisch, M., Giese, B., Hoffmeister, A., Matz, K.-D., Scholten, F., Kuhn, A., Wagner, R., Neukum, G., Helfenstein, P., Porco, C. (2008). "High Resolution Enceladus Atlas derived from Cassini-ISS images." Planetary and Space Science 56, 109-116.


Roatsch, Th., Wählisch, M., Hoffmeister, A., Scholten, F., Matz, K. D., Giese, B., Wagner, R., Kersten, E., Neukum, G., Porco, C. (2008). "Mapping and Cartography of the Icy Saturnian Satellites Using Cassini ISS Images" The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XXXVII. Part B4, 1011-1016.


McKay, C. P., Porco, C. C., Altheide,T., Davis,W. L., Kral,T. A. (2008). "The Possible Origin and Persistence of Life on Enceladus and Detection of Biomarkers in the Plume" Astrobiology 8, 909-919.




2007
Porco, C., Thomas, P., Weiss, J., Richardson, D. (2007). "Saturn's Small Inner Satellites: Clues to Their Origins." Science 318, 1602-1607.


Charnoz S., Brahic A., Thomas P., Porco C. (2007). "The equatorial ridges of Pan & Atlas: terminal accretionary ornaments?" Science 318, 1622-1624.


Giese, B., Wagner, R., Neukum, G., Helfenstein, P., and Thomas, P. (2007). "Tethys: Lithospheric thickness and heat flux from flexurally supported topography at Ithaca Chasma." Geophysical Research Letters Vol. 34, L21203.




Dyudina, U., Ingersoll, A., Ewald, S., Porco, C., Fischer, G., Kurth, W., Desch, M., Del Genio, A., Barbara, J., Ferrier, J. (2007). "Lightning Storms on Saturn observed by Cassini ISS and RPWS during 2004-2006." Icarus 190, 545-555.


Fischer, G., Kurth, W., Dyudina, U., Kaiser, M., Zarka, P., Lecacheux, A., Ingersoll, A., Gurnett, D. (2007). "Analysis of a giant lightning storm on Saturn." Icarus 190, 528-544.


Del Genio, A.D., Barbara, J.M., Ferrier, J., Ingersoll, A.P., West, R.A., Vasavada, A.R., Spitale, J., Porco, C.C. (2007). "Saturn Eddy Momentum Fluxes and Convection: First Estimates from Cassini Images." Icarus 189, 479-492.


Hedman, M.M., Burns, J.A., Tiscareno, M.S., Porco, C.C., Jones, G.H., Roussos, E., Krupp, N., Paranicas, C., Kempf, S. (2007). "The Source of Saturn’s G Ring." Science 317, 653-656.


Thomas, P.C., Burns, J.A., Helfenstein, P., Squyres, S., Veverka, J., Porco, C., Turtle, E., McEwen, A., Denk, T., Giese, B., Roatsch, T., Johnson, T.V., Jacobson, R.A. (2007). "Shapes of the Saturnian icy satellites and their significance." Icarus 190, 573-584.


Tiscareno, M.S., Burns, J.A., Nicholson, P.D., Hedman, M.M., Porco, C.C. (2007). "Cassini Imaging of Saturn's Rings II: A Wavelet Technique for Analysis of Density Waves and Other Radial Structure in the Rings." Icarus 189, 14-34.


Thomas, P., Armstrong, J., Asmar, S.W., Burns, J.A., Denk, T., Giese, B., Helfenstein, P., Iess, L., Johnson, T.V., McEwen, A., Nicolaisen, L., Porco, C., Rappaport, N., Richardson, J., Somenzi, L., Tottora, P., Turtle. E.P., Veverka, J. (2007). "Hyperion's sponge-like appearance." Nature 448, 50-53.


Hedman, M.M. Burns, J.A., Showalter, M.R., Porco, C.C., Nicholson, P.D., Bosh, A.S., Tiscareno, M.S., Brown, R.H., Buratti, B.J., Baines, K.H., Clark, R. (2007). "Saturn's Dynamic D-Ring." Icarus 188, 89-107.




2006
Li, L., Ingersoll, A.P., Vasavada, A.R., Simon-Miller, A.A., Achterberg, R.K., Ewald, S.P., Dyudina, U.A., Porco, C.C., West, R.A., Flasar, F.M. (2006). "Waves in Jupiter's atmosphere observed by the Cassini ISS and CIRS instruments." Icarus 185, 416-419.


Tiscareno, M.S., Nicholson, P.D., Burns, J.A., Hedman, M.M., Porco, C.C. (2006). "Unraveling Temporal Variability in Saturn's Spiral Density Waves: Results and Predictions." Astrophysical Journal Letters 651, L65-L68.


Roatsch, Th., Wahlisch, M., Scholten, F., Hoffmeister, A., Matz, K.-D., Denk, T., Neukum, G., Thomas, P., Helfenstein, P., Porco, C. (2006). "Mapping of the icy Saturnian satellites: First results from Cassini-ISS." Planetary and Space Science 54, 1137-1145.


Giese, B., Neukum, G., Roatsch, T., Denk, T., Porco, C.C. (2006). "Topographic modeling of Phoebe using Cassini images." Planetary and Space Science 54, 1156-1166.


Spitale, J.N., Jacobson, R.A., Porco, C.C., Owen, W.M., Jr. (2006). "The Orbits of Saturn's Small Satellites Derived from Combined Historic and Cassini Imaging Observations." Astronomical Journal 132, 692-710.


Jacobson, R.A. Spitale, J., Porco, C.C., Owen, W.M., Jr. (2006). "The GM Values of Mimas and Tethys and the Libration of Methone." Astronomical Journal 132, 711-713.


Vasavada, A.R., Horst, S.M., Kennedy, M.R., Ingersoll, A.P., Porco, C.C., Del Genio, A.D., West, R.A. (2006). "Cassini imaging of Saturn: Southern hemisphere winds and vortices." Journal of Geophysical Research-Planets 111, E05004.


Li, L., Ingersoll, A.P., Vasavada, A.R., Simon-Miller, A.A., Del Genio, A.D., Ewald, S.P., Porco, C.C., West, R.A. (2006). "Vertical Wind Shear on Jupiter from Cassini Images." Journal of Geophysical Research-Planets 111, E04004.


Tiscareno, M.S., Burns, J.A., Hedman, M.M., Porco, C.C., Weiss, J.W., Dones, L., Richardson, D.C., Murray, C.D. (2006). "100-metre-diameter Moonlets in Saturn's A-ring from Observations of 'Propeller' Structures." Nature 440, 648-650.


Mitchell, C.J., Horanyi, M., Havnes, O., Porco, C.C. (2006). "Saturn's Spokes: Lost and Found." Science 311, 1587-1589.


Cooper, N.J., Murray, C.D., Porco, C.C., Spitale, J.N. (2006). "Cassini ISS Astrometric Observations of the Inner Jovian Satellites, Amalthea and Thebe." Icarus 181, 223-234.




2005
Charnoz, S., Porco, C.C., Deau, E., Brahic, A., Spitale, J.N., Bacques, G., Baillie, K. (2005). "Cassini Discovers a Kinematic Spiral Ring around Saturn." Science 310, 1241-1351.


Murray, C.D., Chavez, C., Beurle, K., Cooper, N., Evans, M.W., Burns, J.A., Porco, C.C. (2005). "How Prometheus creates structure in Saturn's F ring." Nature 437, 1326-1329.


Dyudina, U.A., Sackett, P.D., Bayliss, D.D.R., Seager, S., Porco, C.C., Throop, H.B., Dones, L. (2005). "Phase Light Curves for Extrasolar Jupiters and Saturns." Astrophysical Journal 618, 973-986.




2004
Throop, H.B., Porco, C.C., West, R.A., Burns, J.A., Showalter, M.R., Nicholson, P. D. (2004). "The Jovian Rings: New Results Derived from Cassini, Galileo, Voyager and Earth-based Observations." Icarus 172, 59-77.


Li, L., Ingersoll, A.P., Vasavada, A.R., Porco, C.C., del Genio, A.D., Ewald, S.P. (2004). "Life Cycles of Spots on Jupiter from Cassini Images." Icarus 172, 9-23.


Geissler, P., McEwen, A., Porco, C., Strobel, D., Saur, J., Ajello, J., West, R. (2004). "Cassini Observations of Io's Visible Aurorae." Icarus 172, 127-140.


Dyudina, U.A., del Genio, A.D., Ingersoll, A.P., Porco, C.C., West, R.A., Vasavada, A.R., Barbara, J.M. (2004). "Lightning on Jupiter Observed by Cassini ISS Camera and the Strength of the H-alpha Line in the Lightning Spectrum." Icarus 172, 24-36.