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602 results on '"Phillips, Roger J."'

1. PREFACE

Author

Bougher, Stephen W., primary, Hunten, Donald M., additional, and Phillips, Roger J., additional

Published
2022
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5. The curious case of Mercury's internal structure

Author

Hauck, Steven A, Margot, Jean‐Luc, Solomon, Sean C, Phillips, Roger J, Johnson, Catherine L, Lemoine, Frank G, Mazarico, Erwan, McCoy, Timothy J, Padovan, Sebastiano, Peale, Stanton J, Perry, Mark E, Smith, David E, and Zuber, Maria T

Subjects
Mercury, Internal Structure, MESSENGER, interior, Astronomical and Space Sciences, Geochemistry, Geology
Abstract

The recent determination of the gravity field of Mercury and new Earth-based radar observations of the planet's spin state afford the opportunity to explore Mercury's internal structure. These observations provide estimates of two measures of the radial mass distribution of Mercury: the normalized polar moment of inertia and the fractional polar moment of inertia of the solid portion of the planet overlying the liquid core. Employing Monte Carlo techniques, we calculate several million models of the radial density structure of Mercury consistent with its radius and bulk density and constrained by these moment of inertia parameters. We estimate that the top of the liquid core is at a radius of 2020 ± 30 km, the mean density above this boundary is 3380 ± 200 kg m-3, and the density below the boundary is 6980 ± 280 kg m-3. We find that these internal structure parameters are robust across a broad range of compositional models for the core and planet as a whole. Geochemical observations of Mercury's surface by MESSENGER indicate a chemically reducing environment that would favor the partitioning of silicon or both silicon and sulfur into the metallic core during core-mantle differentiation. For a core composed of Fe-S-Si materials, the thermodynamic properties at elevated pressures and temperatures suggest that an FeS-rich layer could form at the top of the core and that a portion of it may be presently solid. Key PointsNew MESSENGER and Earth-based radar data provide Mercury's moments of inertiaMercury's core-mantle boundary is 420 +/- 30 km below the planet's surfaceThe core may be compositionally segregated ©2013. American Geophysical Union. All Rights Reserved.

Published
2013

6. Radar Soundings of the Subsurface of Mars

Author

Picardi, Giovanni, Plaut, Jeffrey J., Biccari, Daniela, Bombaci, Ornella, Calabrese, Diego, Cartacci, Marco, Cicchetti, Andrea, Clifford, Stephen M., Edenhofer, Peter, Farrell, William M., Federico, Costanzo, Frigeri, Alessandro, Gurnett, Donald A., Hagfors, Tor, Heggy, Essam, Herique, Alain, Huff, Richard L., Ivanov, Anton B., Jordan, Rolando L., Kirchner, Donald L., Kofman, Wlodek, Leuschen, Carlton J., Nielsen, Erling, Orosei, Roberto, Pettinelli, Elena, Phillips, Roger J., Plettemeier, Dirk, Safaeinili, Ali, Seu, Roberto, Stofan, Ellen R., Vannaroni, Giuliano, Watters, Thomas R., and Zampolini, Enrico

Published
2005

7. New Perspectives on Ancient Mars

Author

Solomon, Sean C., Aharonson, Oded, Aurnou, Jonathan M., Banerdt, W. Bruce, Carr, Michael H., Dombard, Andrew J., Frey, Herbert V., Golombek, Matthew P., Hauck, Steven A., Head, James W., Jakosky, Bruce M., Johnson, Catherine L., McGovern, Patrick J., Neumann, Gregory A., Phillips, Roger J., Smith, David E., and Zuber, Maria T.

Published
2005

9. The Geophysics of Mercury: Current Status and Anticipated Insights from the MESSENGER Mission

Author

Zuber, Maria T, Aharonson, Oded, Aurnou, Jonathan M, Cheng, Andrew F, Hauck, Steven A, Heimpel, Moritz H, Neumann, Gregory A, Peale, Stanton J, Phillips, Roger J, Smith, David E, Solomon, Sean C, and Stanley, Sabine

Subjects
Clinical Research, Mercury, MESSENGER, core, rotational state, magnetic dynamos, thermal history, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract

Current geophysical knowledge of the planet Mercury is based upon observations from ground-based astronomy and flybys of the Mariner 10 spacecraft, along with theoretical and computational studies. Mercury has the highest uncompressed density of the terrestrial planets and by implication has a metallic core with a radius approximately 75% of the planetary radius. Mercury's spin rate is stably locked at 1.5 times the orbital mean motion. Capture into this state is the natural result of tidal evolution if this is the only dissipative process affecting the spin, but the capture probability is enhanced if Mercury's core were molten at the time of capture. The discovery of Mercury's magnetic field by Mariner 10 suggests the possibility that the core is partially molten to the present, a result that is surprising given the planet's size and a surface crater density indicative of early cessation of significant volcanic activity. A present-day liquid outer core within Mercury would require either a core sulfur content of at least several weight percent or an unusual history of heat loss from the planet's core and silicate fraction. A crustal remanent contribution to Mercury's observed magnetic field cannot be ruled out on the basis of current knowledge. Measurements from the MESSENGER orbiter, in combination with continued ground-based observations, hold the promise of setting on a firmer basis our understanding of the structure and evolution of Mercury's interior and the relationship of that evolution to the planet's geological history. © 2007 Springer Science+Business Media B.V.

Published
2007

13. The Global Topography of Mars and Implications for Surface Evolution

Author

Smith, David E., Zuber, Maria T., Solomon, Sean C., Phillips, Roger J., Head, James W., Garvin, James B., Banerdt, W. Bruce, Muhleman, Duane O., Pettengill, Gordon H., Neumann, Gregory A., Lemoine, Frank G., Abshire, James B., Aharonson, Oded, Brown, C. David, Hauck, Steven A., Ivanov, Anton B., McGovern, Patrick J., Zwally, H. Jay, and Duxbury, Thomas C.

Published
1999

14. Signatures of Higgs-Triplet Representations at Tev--e+e- Colliders

Author

Cheung, Kingman, Phillips, Roger J. N., and Pilaftsis, Apostolos

Subjects
High Energy Physics - Phenomenology
Abstract

We investigate the potential of future TeV linear e^+e^- colliders to observe singly-charged Higgs bosons ($H^\pm$) via the coupling $H^\pm W^\mp Z$, which would signal the existence of exotic Higgs representations. In the context of a Higgs-triplet model compatible with the electroweak oblique parameters, we estimate the cross section for pro- ducing charged Higgs-triplet bosons that couple predominantly to $W$ and $Z$ bosons in 0.5--2 TeV-$e^+e^-$ colliders. The principal backgrounds are evaluated and the viability of the signal is discussed and illustrated., Comment: LaTeX, 20 pages, 4 figures

Published
1994
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15. Observations of the North Polar Region of Mars from the Mars Orbiter Laser Altimeter

Author

Zuber, Maria T., Smith, David E., Solomon, Sean C., Abshire, James B., Afzal, Robert S., Aharonson, Oded, Fishbaugh, Kathryn, Ford, Peter G., Frey, Herbert V., Garvin, James B., Head, James W., Ivanov, Anton B., Johnson, Catherine L., Muhleman, Duane O., Neumann, Gregory A., Pettengill, Gordon H., Phillips, Roger J., Sun, Xiaoli, Zwally, H. Jay, Banerdt, W. Bruce, and Duxbury, Thomas C.

Published
1998

17. Gravity field of the Orientale basin from the Gravity Recovery and Interior Laboratory Mission

Author

Zuber, Maria T., Smith, David E., Neumann, Gregory A., Goossens, Sander, Andrews-Hanna, Jeffrey C., Head, James W., Kiefer, Walter S., Asmar, Sami W., Konopliv, Alexander S., Lemoine, Frank G., Matsuyama, Isamu, Melosh, H. Jay, McGovern, Patrick J., Nimmo, Francis, Phillips, Roger J., Solomon, Sean C., Taylor, G. Jeffrey, Watkins, Michael M., Wieczorek, Mark A., Williams, James G., Jansen, Johanna C., Johnson, Brandon C., Keane, James T., Mazarico, Erwan, Miljković, Katarina, Park, Ryan S., Soderblom, Jason M., and Yuan, Dah-Ning

Published
2016

26. Jets

Author

Barger, Vernon D., primary and Phillips, Roger J. N., additional

Published
2018
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37. MESSENGER at Mercury: Early orbital operations

Author

McNutt, Ralph L., Jr., Solomon, Sean C., Bedini, Peter D., Anderson, Brian J., Blewett, David T., Evans, Larry G., Gold, Robert E., Krimigis, Stamatios M., Murchie, Scott L., Nittler, Larry R., Phillips, Roger J., Prockter, Louise M., Slavin, James A., Zuber, Maria T., Finnegan, Eric J., and Grant, David G.

Published
2014
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40. The Origin of Lunar Mascon Basins

Author

Melosh, H. J., Freed, Andrew M., Johnson, Brandon C., Blair, David M., Andrews-Hanna, Jeffrey C., Neumann, Gregory A., Phillips, Roger J., Smith, David E., Solomon, Sean C., Wieczorek, Mark A., and Zuber, Maria T.

Published
2013
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43. The Crust of the Moon as Seen by GRAIL

Author

Wieczorek, Mark A., Neumann, Gregory A., Nimmo, Francis, Kiefer, Walter S., Taylor, G. Jeffrey, Melosh, H. Jay, Phillips, Roger J., Solomon, Sean C., Andrews-Hanna, Jeffrey C., Asmar, Sami W., Konopliv, Alexander S., Lemoine, Frank G., Smith, David E., Watkins, Michael M., Williams, James G., and Zuber, Maria T.

Published
2013
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44. Ancient Igneous Intrusions and Early Expansion of the Moon Revealed by GRAIL Gravity Gradiometry

Author

Andrews-Hanna, Jeffrey C., Asmar, Sami W., Head, James W., Kiefer, Walter S., Konopliv, Alexander S., Lemoine, Frank G., Matsuyama, Isamu, Mazarico, Erwan, McGovern, Patrick J., Melosh, H. Jay, Neumann, Gregory A., Nimmo, Francis, Phillips, Roger J., Smith, David E., Solomon, Sean C., Taylor, G. Jeffrey, Wieczorek, Mark A., Williams, James G., and Zuber, Maria T.

Published
2013
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45. Gravity Field and Internal Structure of Mercury from MESSENGER

Author

Smith, David E., Zuber, Maria T., Phillips, Roger J., Solomon, Sean C., Hauck, Steven A., Lemoine, Frank G., Mazarico, Erwan, Neumann, Gregory A., Peale, Stanton J., Margot, Jean-Luc, Johnson, Catherine L., Torrence, Mark H., Perry, Mark E., Rowlands, David D., Goossens, Sander, Head, James W., and Taylor, Anthony H.

Published
2012
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46. Topography of the Northern Hemisphere of Mercury from MESSENGER Laser Altimetry

Author

Zuber, María T., Smith, David E., Phillips, Roger J., Solomon, Sean C., Neumann, Gregory A., Hauck, Steven A., Peale, Stanton J., Barnouin, Olivier S., Head, James W., Johnson, Catherine L., Lemoine, Frank G., Mazarico, Erwan, Sun, Xiaoli, Torrence, Mark H., Freed, Andrew M., Klimczak, Christian, Margot, Jean-Luc, Oberst, Jürgen, Perry, Mark E., McNutt, Ralph L., Balcerski, Jeffrey A., Michel, Nathalie, Talpe, Matthieu J., and Di Yang

Published
2012
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