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437 results on '"Johnson, T. V"'

1. On the volatile enrichments and heavy element content in HD 189733b

Author

Mousis, O., Lunine, J. I., Petit, J. -M., Zahnle, K., Biennier, L., Picaud, S., Johnson, T. V., Mitchell, J. B. A., Boudon, V., Cordier, D., Devel, M., Georges, R., Griffith, C., Iro, N., Marley, M. S., and Marboeuf, U.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Favored theories of giant planet formation center around two main paradigms, namely the core accretion model and the gravitational instability model. These two formation scenarios support the hypothesis that the giant planet metallicities should be higher or equal to that of the parent star. Meanwhile, spectra of the transiting hot Jupiter HD189733b suggest that carbon and oxygen abundances range from depleted to enriched with respect to the star. Here, using a model describing the formation sequence and composition of planetesimals in the protoplanetary disk, we determine the range of volatile abundances in the envelope of HD189733b that is consistent with the 20--80 Earth-masses of heavy elements estimated to be present in the planet's envelope. We then compare the inferred carbon and oxygen abundances to those retrieved from spectroscopy and we find a range of supersolar values that directly fit both spectra and internal structure models. In some cases, we find that the apparent contradiction between the subsolar elemental abundances and the {mass of heavy elements predicted in HD189733b by internal structure models} can be explained by the presence of large amounts of carbon molecules in the form of polycyclic aromatic hydrocarbons and soots in the upper layers of the envelope, as suggested by recent photochemical models. A diagnostic test that would confirm the presence of these compounds in the envelope is the detection of acetylene., Comment: Accepted for publication in The Astrophysical Journal

Published
2010
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2. Cassini Observes the Active South Pole of Enceladus

Author

Porco, C. C., Helfenstein, P., Thomas, P. C., Ingersoll, A. P., Wisdom, J., West, R., Neukum, G., Denk, T., Wagner, R., Roatsch, T., Kieffer, S., Turtle, E., McEwen, A., Johnson, T. V., Rathbun, J., Veverka, J., Wilson, D., Perry, J., Spitale, J., Brahic, A., Burns, J. A., DelGenio, A. D., Dones, L., Murray, C. D., and Squyres, S.

Published
2006

3. Cassini Imaging Science: Initial Results on Saturn's Atmosphere

Author

Porco, C. C., Baker, E., Barbara, J., Beurle, K., Brahic, A., Burns, J. A., Charnoz, S., Cooper, N., Dawson, D. D., Del Genio, A. D., Denk, T., Dones, L., Dyudina, U., Evans, M. W., Giese, B., Grazier, K., Helfenstein, P., Ingersoll, A. P., Jacobson, R. A., Johnson, T. V., McEwen, A., Murray, C. D., Neukum, G., Owen, W. M., Perry, J., Roatsch, T., Spitale, J., Squyres, S., Thomas, P., Tiscareno, M., Turtle, E., Vasavada, A. R., Veverka, J., Wagner, R., and West, R.

Published
2005

4. Cassini Imaging Science: Initial Results on Phoebe and Iapetus

Author

Porco, C. C., Baker, E., Barbara, J., Beurle, K., Brahic, A., Burns, J. A., Charnoz, S., Cooper, N., Dawson, D. D., Del Genio, A. D., Denk, T., Dones, L., Dyudina, U., Evans, M. W., Giese, B., Grazier, K., Helfenstein, P., Ingersoll, A. P., Jacobson, R. A., Johnson, T. V., McEwen, A., Murray, C. D., Neukum, G., Owen, W. M., Perry, J., Roatsch, T., Spitale, J., Squyres, S., Thomas, P. C., Tiscareno, M., Turtle, E., Vasavada, A. R., Veverka, J., Wagner, R., and West, R.

Published
2005

5. Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites

Author

Porco, C. C., Baker, E., Barbara, J., Beurle, K., Brahic, A., Burns, J. A., Charnoz, S., Cooper, N., Dawson, D. D., Del Genio, A. D., Denk, T., Dones, L., Dyudina, U., Evans, M. W., Giese, B., Grazier, K., Helfenstein, P., Ingersoll, A. P., Jacobson, R. A., Johnson, T. V., McEwen, A., Murray, C. D., Neukum, G., Owen, W. M., Perry, J., Roatsch, T., Spitale, J., Squyres, S., Thomas, P., Tiscareno, M., Turtle, E., Vasavada, A. R., Veverka, J., Wagner, R., and West, R.

Published
2005

6. Galileo at Io: Results from High-Resolution Imaging

Author

McEwen, A. S., Belton, M. J. S., Breneman, H. H., Fagents, S. A., Geissler, P., Greeley, R., Head, J. W., Hoppa, G., Jaeger, W. L., Johnson, T. V., Keszthelyi, L., Klaasen, K. P., Lopes-Gautier, R., Magee, K. P., Milazzo, M. P., Moore, J. M., Pappalardo, R. T., Phillips, C. B., Radebaugh, J., Schubert, G., Schuster, P., Simonelli, D. P., Sullivan, R., Thomas, P. C., Turtle, E. P., and Williams, D. A.

Published
2000

8. High-Temperature Silicate Volcanism on Jupiter's Moon Io

Author

McEwen, A. S., Keszthelyi, L., Spencer, J. R., Schubert, G., Matson, D. L., Lopes-Gautier, R., Klaasen, K. P., Johnson, T. V., Head, J. W., Geissler, P., Fagents, S., Davies, A. G., Carr, M. H., Breneman, H. H., and Belton, M. J. S.

Published
1998

11. Galileo's First Images of Jupiter and the Galilean Satellites

Author

Belton, M. J. S., Head, J. W., Ingersoll, A. P., Greeley, R., McEwen, A. S., Klaasen, K. P., Senske, D., Pappalardo, R., Collins, G., Vasavada, A. R., Sullivan, R., Simonelli, D., Geissler, P., Carr, M. H., Davies, M. E., Veverka, J., Gierasch, P. J., Banfield, D., Bell, M., Chapman, C. R., Anger, C., Greenberg, R., Neukum, G., Pilcher, C. B., Beebe, R. F., Burns, J. A., Fanale, F., Ip, W., Johnson, T. V., Morrison, D., Moore, J., Orton, G. S., Thomas, P., and West, R. A.

Published
1996

13. The Cassini Cosmic Dust Analyzer

Author

Srama, R., Ahrens, T. J., Altobelli, N., Auer, S., Bradley, J. G., Burton, M., Dikarev, V. V., Economou, T., Fechtig, H., Görlich, M., Grande, M., Graps, A., Grün, E., Havnes, O., Helfert, S., Horanyi, M., Igenbergs, E., Jessberger, E. K., Johnson, T. V., Kempf, S., Krivov, A. V., Krüger, H., Mocker-Ahlreep, A., Moragas-Klostermeyer, G., Lamy, P., Landgraf, M., Linkert, D., Linkert, G., Lura, F., McDonnell, J. A. M., Möhlmann, D., Morfill, G. E., Müller, M., Roy, M., Schäfer, G., Schlotzhauer, G., Schwehm, G. H., Spahn, F., Stübig, M., Svestka, J., Tschernjawski, V., Tuzzolino, A. J., Wäsch, R., Zook, H. A., and Russell, Christopher T., editor

Published
2004
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19. Galileo Infrared Imaging Spectroscopy Measurements at Venus

Author

Carlson, R. W., Baines, K. H., Taylor, F. W., Drossart, P., Kamp, L. W., Pollack, J. B., Lellouch, E., Collard, A. D., Calcutt, S. B., Grinspoon, D., Weissman, P. R., Smythe, W. D., Ocampo, A. C., Danielson, G. E., Fanale, F. P., Johnson, T. V., Kieffer, H. H., Matson, D. L., McCord, T. B., and Soderblom, L. A.

Published
1991

20. Galileo Encounter with 951 Gaspra: First Pictures of an Asteroid

Author

Belton, M. J. S., Veverka, J., Thomas, P., Helfenstein, P., Simonelli, D., Chapman, C., Davies, M. E., Greeley, R., Greenberg, R., Head, J., Murchie, S., Klaasen, K., Johnson, T. V., McEwen, A., Morrison, D., Neukum, G., Fanale, F., Anger, C., Carr, M., and Pilcher, C.

Published
1992

21. Voyager 2 at Neptune: Imaging Science Results

Author

Smith, B. A., Soderblom, L. A., Banfield, D., Barnet, C., Basilevksy, A. T., Beebe, R. F., Bollinger, K., Boyce, J. M., Brahic, A., Briggs, G. A., Brown, R. H., Chyba, C., Collins, S. A., Colvin, T., Cook, A. F., Crisp, D., Croft, S. K., Cruikshank, D., Cuzzi, J. N., Danielson, G. E., Davies, M. E., De Jong, E., Dones, L., Godfrey, D., Goguen, J., Grenier, I., Haemmerle, V. R., Hammel, H., Hansen, C. J., Helfenstein, C. P., Howell, C., Hunt, G. E., Ingersoll, A. P., Johnson, T. V., Kargel, J., Kirk, R., Kuehn, D. I., Limaye, S., Masursky, H., McEwen, A., Morrison, D., Owen, T., Owen, W., Pollack, J. B., Porco, C. C., Rages, K., Rogers, P., Rudy, D., Sagan, C., Schwartz, J., Shoemaker, E. M., Showalter, M., Sicardy, B., Simonelli, D., Spencer, J., Sromovsky, L. A., Stoker, C., Strom, R. G., Suomi, V. E., Synott, S. P., Terrile, R. J., Thomas, P., Thompson, W. R., Verbiscer, A., and Veverka, J.

Published
1989

25. Voyager 2 in the Uranian System: Imaging Science Results

Author

Smith, B. A., Soderblom, L. A., Beebe, R., Bliss, D., Boyce, J. M., Brahic, A., Briggs, G. A., Brown, R. H., Collins, S. A., Cook, A. F., Croft, S. K., Cuzzi, J. N., Danielson, G. E., Davies, M. E., Dowling, T. E., Godfrey, D., Hansen, C. J., Harris, C., Hunt, G. E., Ingersoll, A. P., Johnson, T. V., Krauss, R. J., Masursky, H., Morrison, D., Owen, T., Plescia, J. B., Pollack, J. B., Porco, C. C., Rages, K., Sagan, C., Shoemaker, E. M., Sromovsky, L. A., Stoker, C., Strom, R. G., Suomi, V. E., Synnott, S. P., Terrile, R. J., Thomas, P., Thompson, W. R., and Veverka, J.

Published
1986

26. Galileo Multispectral Imaging of the North Polar and Eastern Limb Regions of the Moon

Author

Belton, M. J. S., Greeley, R., Greenberg, R., McEwen, A., Klaasen, K. P., Head, J. W., Pieters, C., Neukum, G., Chapman, C. R., Geissler, P., Heffernan, C., Breneman, H., Anger, C., Carr, M. H., Davies, M. E., Fanale, F. P., Gierasch, P. J., Ingersoll, A. P., Johnson, T. V., Pilcher, C. B., Thompson, W. R., Veverka, J., and Sagan, C.

Published
1994

27. The cosmic dust analyser onboard cassini: ten years of discoveries

Author

Srama, R., Kempf, S., Moragas-Klostermeyer, G., Altobelli, N., Auer, S., Beckmann, U., Bugiel, S., Burton, M., Economomou, T., Fechtig, H., Fiege, K., Green, S. F., Grande, M., Havnes, O., Hillier, J. K., Helfert, S., Horanyi, M., Hsu, S., Igenbergs, E., Jessberger, E. K., Johnson, T. V., Khalisi, E., Krüger, H., Matt, G., Mocker, A., Lamy, P., Linkert, G., Lura, F., Möhlmann, D., Morfill, G. E., Otto, K., Postberg, F., Roy, M., Schmidt, J., Schwehm, G. H., Spahn, F., Sterken, V., Svestka, J., Tschernjawski, V., Grün, E., and Röser, H.-P.

Published
2011
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31. Evolution of Planetesimals Accreted in the Early Solar System

Author

Matson, D. L, Johnson, T. V, Castillo-Rogez, J. C, and Thomas, P. C

Subjects
Lunar And Planetary Science And Exploration
Abstract

The purpose of this presentation is to point out that the origins and abundances of short-lived nu-clides in the early solar system had important conse-quences for "icy planetesimals". It is believed that these planetesimals, composed of ice and rock, were once very abundant in the early, outer solar system. Today, spacecraft can visit remnants of that popula-tion and measure their properties. Cassini's flyby of Saturn's satellite Phoebe may have been the first visit to an object related to this population.

Published
2011

32. Enceladus: Starting Hydrothermal Activity

Author

Matson, D. L, Castillo-Rogez, J. C, Johnson, T. V, Lunine, J. I, and Davies, A. G

Subjects
Geophysics, Lunar And Planetary Science And Exploration
Abstract

We describe a process for starting the hydrothermal activity in Enceladus' South Polar Region. The process takes advantage of fissures that reach the water table, about 1 kilometer below the surface. Filling these fissures with fresh ocean water initiates a flow of water up from an ocean that can be self-sustaining. In this hypothesis the heat to sustain the thermal anomalies and the plumes comes from a slightly warm ocean at depth. The heat is brought to the surface by water that circulates up, through the crust and then returns to the ocean.

Published
2011

33. Enceladus' Hydrothermal Activity

Author

Matson, D. L, Castillo-Rogez, J. C, Johnson, T. V, Lunine, J. I, and Davies, A. G

Subjects
Lunar And Planetary Science And Exploration
Published
2011

35. Hyperion's sponge-like appearance

Author

Thomas, P. C., Armstrong, J. W., Asmar, S. W., Burns, J. A., Denk, T., Giese, B., Helfenstein, P., Less, L., Johnson, T. V., McEwen, A., Nicolaisen, L., Porco, C., Rappaport, N., Richardson, J., Somenzi, L., Tortora, P., Turtle, E. P., and Veverka, J.

Published
2007
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37. Cassini Observes the Active South Pole of Enceladus

Author

Porco, C. C, Helfenstein P, Thomas, P. C, Ingersoll, A. P, Wisdom, J, West, R, Neukum, G, Denk, T, Wagner, R, Roatsch, T, Kieffer, S, Turtle, E, McEwen, A, Johnson, T. V, Rathbun, J, Veverka, J, Wilson, D, Perry, J, Spitale, J, Brahic, A, Burns, J. A, DelGenio, A. D, Dones, L, Murray, C. D, and Squyres, S

Subjects
Astronomy
Abstract

Cassini has identified a geologically active province a the south pole of Saturn's moon Enceladus. The shape of Enceladus suggests a possible intense heating epoch in the past by capture into a 1:4 secondary spin/orbit resonance.

Published
2007
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42. Saturn Satellite Densities and the C/O Chemistry of the Solar Nebula

Author

Johnson, T. V and Lunine, J. I

Subjects
Lunar And Planetary Science And Exploration
Abstract

The composition of material condensed in the outer solar system is very dependent on the state of carbon and oxygen in the solar or circumplanetary nebula, since oxygen is the dominant solid-forming element in a solar composition gas (in the form of silicates and water ice), and carbon is about half as abundant. Past discussions of solid material formed in these regions have focused on differences expected between material formed near giant planets where carbon is generally expected to be in the reduced, CH4, form and material formed in the outer protoplanetary solar nebula where CO is believed to be the dominant form [1]. The composition and expected density of these materials are quite sensitive to the C and O solar abundances in all these models. We discuss here the effects of recently suggested modifications to solar abundances on the interpretation of the mean densities for satellites in the Saturn system.

Published
2005

44. Galileo photometry of asteroid 951 Gaspra

Author

Helfenstein, P., Veverka, J., Thomas, P.C., Simonelli, D.P., Lee, P., Klaasen, K., Johnson, T. V., Breneman, H., Head, J.W., Murchie S., Fanale, F., Robinson, M., Clark, B., Granahan, J., Garbeil, H., McEwen, A.S., Kirk, R.L., Davies, M., Neukum, G., Mottola, S., Wagner, R., Belton, M., Chapman, C., and Pilcher, Carl

Subjects
Astronomical photometry -- Usage, Gaspra (Asteroid) -- Research, Astronomy, Earth sciences
Abstract

Photometric studies of the images of asteroid 951 Gaspra, taken by the Galileo space craft during the October 1991 flyby, reveal the particle-phase function characteristics and microscopic texture of the asteroid. The texture and phase function characteristics are similar to those of other asteroids and the moon. The particle scattering albedo is 0.36 and the macroscopic surface roughness parameter is 29 degrees.

Published
1994

45. Loki Patera as the Surface of a Magma Sea

Author

Matson, D. L, Davies, A. G, Veeder, G. J, Rathbun, J. A, and Johnson, T. V

Subjects
Lunar And Planetary Science And Exploration
Abstract

Inspired by the finding of Schubert et al that Io's figure is consistent with a hydrostatic shape, we explore the consequences of modeling Loki Patera as the surface of a large magma sea. This model is attractive because of its sheer simplicity and its usefulness in interpreting and predicting observations. Here, we report on that work.

Published
2004

49. Polar Heat Flow on Io

Author

Veeder, G. J, Matson, D. L, Johnson, T. V, Davies, A. G, and Blaney, D. L

Subjects
Lunar And Planetary Science And Exploration
Abstract

Recently, Galileo spacecraft data have revealed Io's polar regions to be much warmer than previously expected. This unexpected development came from Photo-Polarimeter Radiometer (PPR) data which show that the minimum night temperatures are in the range of 90-95 K virtually everywhere on Io. The minimum night temperatures show no dependence upon latitude and, when away from the sunset terminator, they show no dependence upon time of night. This is indeed bizarre behavior for surface units which generally had been assumed to be passive with respect to Io's pervasive volcanism. Night temperatures of 90-95 K at high, polar latitudes are particularly hard to explain. Even assuming infinite thermal inertia, at these latitudes there is insufficient sunlight to support these warm night temperatures. Thus, through the process of elimination of other possibilities, we come to the conclusion that these surfaces are volcanically heated. Taking previously passive units and turning them into new sources of heat flow is a radical departure from previous thermophysical model paradigms. However, the geological interpretation is straight forward. We are simply seeing the effect of old, cool lava flows which cover most of the surface of Io but yet have some heat to radiate. Under these new constraints, we have taken on the challenge of formulating a physical model which quantitatively reproduces all of the observations of Io's thermal emission. In the following we introduce a new parametric model which suffices to identify a previously unrecognized polar component of Io's heat flow.

Published
2003

50. Lava Flows on Io: Modelling Cooling After Solidification

Author

Davies, A. G, Matson, D. L, Veeder, G. J, Johnson, T. V, and Blaney, D. L

Subjects
Lunar And Planetary Science And Exploration
Abstract

We have modeled the cooling of lava bodies on Io after solidification of the lava, a process that has been little explored since Carr (1986). With recent estimates of lava flow thicknesses on Io ranging from 1 m to 10 m, the modeling of thermal emission from active volcanism must take into account the cooling behaviour after the solidification of the lava, which we model using a finite-element model. Once a lava body is fully solidified, the surface temperature decreases faster, as heat loss is no longer buffered by release of latent heat. This is significant as observed surface temperature is often the only clue available to determine lava surface age. We also find that cooling from the base of the lava is an important process that accelerates the solidification of a flow and therefore subsequent cooling. It is necessary to constrain the cooling process in order to better understand temperature-area relationships on Io's surface and to carry out stochastic modelling of lava flow emplacement.

Published
2003

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