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Mousis O, Canup RM. Why the European Space Agency should join the US mission to Uranus. Nature 2024; 629:755-756. [PMID: 38769451 DOI: 10.1038/d41586-024-01470-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
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2
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de Villa K, González-Cataldo F, Militzer B. Double superionicity in icy compounds at planetary interior conditions. Nat Commun 2023; 14:7580. [PMID: 37990010 PMCID: PMC10663582 DOI: 10.1038/s41467-023-42958-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 10/27/2023] [Indexed: 11/23/2023] Open
Abstract
The elements hydrogen, carbon, nitrogen and oxygen are assumed to comprise the bulk of the interiors of the ice giant planets Uranus, Neptune, and sub-Neptune exoplanets. The details of their interior structures have remained largely unknown because it is not understood how the compounds H2O, NH3 and CH4 behave and react once they have been accreted and exposed to high pressures and temperatures. Here we study thirteen H-C-N-O compounds with ab initio computer simulations and demonstrate that they assume a superionic state at elevated temperatures, in which the hydrogen ions diffuse through a stable sublattice that is provided by the larger nuclei. At yet higher temperatures, four of the thirteen compounds undergo a second transition to a novel doubly superionic state, in which the smallest of the heavy nuclei diffuse simultaneously with hydrogen ions through the remaining sublattice. Since this transition and the melting transition at yet higher temperatures are both of first order, this may introduce additional layers in the mantle of ice giant planets and alter their convective patterns.
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Affiliation(s)
- Kyla de Villa
- Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA.
| | - Felipe González-Cataldo
- Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA
| | - Burkhard Militzer
- Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA
- Department of Astronomy, University of California, Berkeley, CA, 94720, USA
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3
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Cohen IJ, Smith EJ, Clark GB, Turner DL, Ellison DH, Clare B, Regoli LH, Kollmann P, Gallagher DT, Holtzman GA, Likar JJ, Morizono T, Shannon M, Vodusek KS. Plasma Environment, Radiation, Structure, and Evolution of the Uranian System (PERSEUS): A Dedicated Orbiter Mission Concept to Study Space Physics at Uranus. SPACE SCIENCE REVIEWS 2023; 219:65. [PMID: 37869526 PMCID: PMC10587260 DOI: 10.1007/s11214-023-01013-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 10/05/2023] [Indexed: 10/24/2023]
Abstract
The Plasma Environment, Radiation, Structure, and Evolution of the Uranian System (PERSEUS) mission concept defines the feasibility and potential scope of a dedicated, standalone Heliophysics orbiter mission to study multiple space physics science objectives at Uranus. Uranus's complex and dynamic magnetosphere presents a unique laboratory to study magnetospheric physics as well as its coupling to the solar wind and the planet's atmosphere, satellites, and rings. From the planet's tilted and offset, rapidly-rotating non-dipolar magnetic field to its seasonally-extreme interactions with the solar wind to its unexpectedly intense electron radiation belts, Uranus hosts a range of outstanding and compelling mysteries relevant to the space physics community. While the exploration of planets other than Earth has largely fallen within the purview of NASA's Planetary Science Division, many targets, like Uranus, also hold immense scientific value and interest to NASA's Heliophysics Division. Exploring and understanding Uranus's magnetosphere is critical to make fundamental gains in magnetospheric physics and the understanding of potential exoplanetary systems and to test the validity of our knowledge of magnetospheric dynamics, moon-magnetosphere interactions, magnetosphere-ionosphere coupling, and solar wind-planetary coupling. The PERSEUS mission concept study, currently at Concept Maturity Level (CML) 4, comprises a feasible payload that provides closure to a range of space physics science objectives in a reliable and mature spacecraft and mission design architecture. The mission is able to close using only a single Mod-1 Next-Generation Radioisotope Thermoelectric Generator (NG-RTG) by leveraging a concept of operations that relies of a significant hibernation mode for a large portion of its 22-day orbit.
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Affiliation(s)
- Ian J Cohen
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Evan J Smith
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - George B Clark
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Drew L Turner
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Donald H Ellison
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Ben Clare
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Leonardo H Regoli
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Peter Kollmann
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | | | - G Allan Holtzman
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Justin J Likar
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Takeshi Morizono
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
| | - Matthew Shannon
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA
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Thermodynamics of diamond formation from hydrocarbon mixtures in planets. Nat Commun 2023; 14:1104. [PMID: 36843123 PMCID: PMC9968715 DOI: 10.1038/s41467-023-36841-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 02/15/2023] [Indexed: 02/28/2023] Open
Abstract
Hydrocarbon mixtures are extremely abundant in the Universe, and diamond formation from them can play a crucial role in shaping the interior structure and evolution of planets. With first-principles accuracy, we first estimate the melting line of diamond, and then reveal the nature of chemical bonding in hydrocarbons at extreme conditions. We finally establish the pressure-temperature phase boundary where it is thermodynamically possible for diamond to form from hydrocarbon mixtures with different atomic fractions of carbon. Notably, here we show a depletion zone at pressures above 200 GPa and temperatures below 3000 K-3500 K where diamond formation is thermodynamically favorable regardless of the carbon atomic fraction, due to a phase separation mechanism. The cooler condition of the interior of Neptune compared to Uranus means that the former is much more likely to contain the depletion zone. Our findings can help explain the dichotomy of the two ice giants manifested by the low luminosity of Uranus, and lead to a better understanding of (exo-)planetary formation and evolution.
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Mandt KE. The first dedicated ice giants mission. Science 2023; 379:640-642. [PMID: 36795812 DOI: 10.1126/science.ade8446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
The mysteries of the Uranus system can be unlocked through interdisciplinary exploration.
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Celliers PM, Millot M. Imaging velocity interferometer system for any reflector (VISAR) diagnostics for high energy density sciences. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:011101. [PMID: 36725591 DOI: 10.1063/5.0123439] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/28/2022] [Indexed: 06/18/2023]
Abstract
Two variants of optical imaging velocimetry, specifically the one-dimensional streaked line-imaging and the two-dimensional time-resolved area-imaging versions of the Velocity Interferometer System for Any Reflector (VISAR), have become important diagnostics in high energy density sciences, including inertial confinement fusion and dynamic compression of condensed matter. Here, we give a brief review of the historical development of these techniques, then describe the current implementations at major high energy density (HED) facilities worldwide, including the OMEGA Laser Facility and the National Ignition Facility. We illustrate the versatility and power of these techniques by reviewing diverse applications of imaging VISARs for gas-gun and laser-driven dynamic compression experiments for materials science, shock physics, condensed matter physics, chemical physics, plasma physics, planetary science and astronomy, as well as a broad range of HED experiments and laser-driven inertial confinement fusion research.
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Affiliation(s)
- Peter M Celliers
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Marius Millot
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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Semi-Analytical Search for Sun-Synchronous and Planet Synchronous Orbits around Jupiter, Saturn, Uranus and Neptune. MATHEMATICS 2022. [DOI: 10.3390/math10152684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
With the development of aerospace science and technology, more and more probes are expected to be deployed around extraterrestrial planets. In this paper, some special orbits around Jupiter, Saturn, Uranus, and Neptune are discussed and analyzed. The design methods of some special orbits are sorted out, considering the actual motion parameters and main perturbation forces of these four planets. The characteristics of sun-synchronous orbits, repeating ground track orbits, and synchronous planet orbits surrounding these plants are analyzed and compared. The analysis results show that Uranus does not have sun-synchronous orbits in the general sense. This paper also preliminarily calculates the orbital parameters of some special orbits around these planets, including the relationship between the semi-major axis, the eccentricity and the orbital inclination of the sun-synchronous orbits, the range of the regression coefficient of the sun-synchronous repeating ground track orbits, and the orbital parameters of synchronous planet orbits, laying a foundation for more accurate orbit design of future planetary probes.
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Ranieri U, Conway LJ, Donnelly ME, Hu H, Wang M, Dalladay-Simpson P, Peña-Alvarez M, Gregoryanz E, Hermann A, Howie RT. Formation and Stability of Dense Methane-Hydrogen Compounds. PHYSICAL REVIEW LETTERS 2022; 128:215702. [PMID: 35687440 DOI: 10.1103/physrevlett.128.215702] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 02/02/2022] [Accepted: 04/20/2022] [Indexed: 06/15/2023]
Abstract
Through a series of x-ray diffraction, optical spectroscopy diamond anvil cell experiments, combined with density functional theory calculations, we explore the dense CH_{4}-H_{2} system. We find that pressures as low as 4.8 GPa can stabilize CH_{4}(H_{2})_{2} and (CH_{4})_{2}H_{2}, with the latter exhibiting extreme hardening of the intramolecular vibrational mode of H_{2} units within the structure. On further compression, a unique structural composition, (CH_{4})_{3}(H_{2})_{25}, emerges. This novel structure holds a vast amount of molecular hydrogen and represents the first compound to surpass 50 wt % H_{2}. These compounds, stabilized by nuclear quantum effects, persist over a broad pressure regime, exceeding 160 GPa.
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Affiliation(s)
- Umbertoluca Ranieri
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
- Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Lewis J Conway
- Centre for Science at Extreme Conditions and The School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, United Kingdom
| | - Mary-Ellen Donnelly
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
| | - Huixin Hu
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
| | - Mengnan Wang
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
| | - Philip Dalladay-Simpson
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
| | - Miriam Peña-Alvarez
- Centre for Science at Extreme Conditions and The School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, United Kingdom
| | - Eugene Gregoryanz
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
- Centre for Science at Extreme Conditions and The School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, United Kingdom
- Key Laboratory of Materials Physics, Institute of Solid State Physics, CAS, Hefei, China
| | - Andreas Hermann
- Centre for Science at Extreme Conditions and The School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, United Kingdom
| | - Ross T Howie
- Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China
- Centre for Science at Extreme Conditions and The School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, United Kingdom
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Teanby NA, Irwin PGJ, Moses JI, Helled R. Neptune and Uranus: ice or rock giants? PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190489. [PMID: 33161863 PMCID: PMC7658781 DOI: 10.1098/rsta.2019.0489] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/04/2020] [Indexed: 05/20/2023]
Abstract
Existing observations of Uranus and Neptune's fundamental physical properties can be fitted with a wide range of interior models. A key parameter in these models is the bulk rock:ice ratio and models broadly fall into ice-dominated (ice giant) and rock-dominated (rock giant) categories. Here we consider how observations of Neptune's atmospheric temperature and composition (H2, He, D/H, CO, CH4, H2O and CS) can provide further constraints. The tropospheric CO profile in particular is highly diagnostic of interior ice content, but is also controversial, with deep values ranging from zero to 0.5 parts per million. Most existing CO profiles imply extreme O/H enrichments of >250 times solar composition, thus favouring an ice giant. However, such high O/H enrichment is not consistent with D/H observations for a fully mixed and equilibrated Neptune. CO and D/H measurements can be reconciled if there is incomplete interior mixing (ice giant) or if tropospheric CO has a solely external source and only exists in the upper troposphere (rock giant). An interior with more rock than ice is also more compatible with likely outer solar system ice sources. We primarily consider Neptune, but similar arguments apply to Uranus, which has comparable C/H and D/H enrichment, but no observed tropospheric CO. While both ice- and rock-dominated models are viable, we suggest a rock giant provides a more consistent match to available atmospheric observations. This article is part of a discussion meeting issue 'Future exploration of ice giant systems'.
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Affiliation(s)
- N. A. Teanby
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - P. G. J. Irwin
- Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK
| | - J. I. Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - R. Helled
- Institute for Computational Science, Center for Theoretical Astrophysics and Cosmology, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
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Lamy L. Auroral emissions from Uranus and Neptune. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190481. [PMID: 33161867 PMCID: PMC7658782 DOI: 10.1098/rsta.2019.0481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/14/2020] [Indexed: 05/20/2023]
Abstract
Uranus and Neptune possess highly tilted/offset magnetic fields whose interaction with the solar wind shapes unique twin asymmetric, highly dynamical, magnetospheres. These radiate complex auroral emissions, both reminiscent of those observed at the other planets and unique to the ice giants, which have been detected at radio and ultraviolet (UV) wavelengths to date. Our current knowledge of these radiations, which probe fundamental planetary properties (magnetic field, rotation period, magnetospheric processes, etc.), still mostly relies on Voyager 2 radio, UV and in situ measurements, when the spacecraft flew by each planet in the 1980s. These pioneering observations were, however, limited in time and sampled specific solar wind/magnetosphere configurations, which significantly vary at various timescales down to a fraction of a planetary rotation. Since then, despite repeated Earth-based observations at similar and other wavelengths, only the Uranian UV aurorae have been re-observed at scarce occasions by the Hubble Space Telescope. These observations revealed auroral features radically different from those seen by Voyager 2, diagnosing yet another solar wind/magnetosphere configuration. Perspectives for the in-depth study of the Uranian and Neptunian auroral processes, with implications for exoplanets, include follow-up remote Earth-based observations and future orbital exploration of one or both ice giant planetary systems. This article is part of a discussion meeting issue 'Future exploration of ice giant systems'.
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Affiliation(s)
- L. Lamy
- LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
- LAM, Pythéas, Aix Marseille Université, CNRS, CNES, 38 Rue Frédéric Joliot Curie, 13013 Marseille, France
- e-mail:
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