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Durante D, Guillot T, Iess L, Stevenson DJ, Mankovich CR, Markham S, Galanti E, Kaspi Y, Zannoni M, Gomez Casajus L, Lari G, Parisi M, Buccino DR, Park RS, Bolton SJ. Juno spacecraft gravity measurements provide evidence for normal modes of Jupiter. Nat Commun 2022; 13:4632. [PMID: 36042221 PMCID: PMC9427753 DOI: 10.1038/s41467-022-32299-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 07/21/2022] [Indexed: 11/25/2022] Open
Abstract
The Juno spacecraft has been collecting data to shed light on the planet’s origin and characterize its interior structure. The onboard gravity science experiment based on X-band and Ka-band dual-frequency Doppler tracking precisely measured Jupiter’s zonal gravitational field. Here, we analyze 22 Juno’s gravity passes to investigate the gravity field. Our analysis provides evidence of new gravity field features, which perturb its otherwise axially symmetric structure with a time-variable component. We show that normal modes of the planet could explain the anomalous signatures present in the Doppler data better than other alternative explanations, such as localized density anomalies and non-axisymmetric components of the static gravity field. We explain Juno data by p-modes having an amplitude spectrum with a peak radial velocity of 10–50 cm/s at 900–1200 μHz (compatible with ground-based observations) and provide upper bounds on lower frequency f-modes (radial velocity smaller than 1 cm/s). The new Juno results could open the possibility of exploring the interior structure of the gas giants through measurements of the time-variable gravity or with onboard instrumentation devoted to the observation of normal modes, which could drive spacecraft operations of future missions. Juno spacecraft experienced unknown accelerations near the closest approach to Jupiter. Here, the authors show that Jupiter’s axially symmetric, north-south asymmetric gravity field measured by Juno is perturbed by a time-variable component, associated to internal oscillations.
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Affiliation(s)
- Daniele Durante
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, Rome, Italy.
| | - Tristan Guillot
- Observatoire de la Côte d'Azur, Université Côte d'Azur, CNRS, Nice, France
| | - Luciano Iess
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, Rome, Italy
| | - David J Stevenson
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Christopher R Mankovich
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Steve Markham
- Observatoire de la Côte d'Azur, Université Côte d'Azur, CNRS, Nice, France
| | - Eli Galanti
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Yohai Kaspi
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Marco Zannoni
- Department of Industrial Engineering, University of Bologna, Forlì, Italy
| | - Luis Gomez Casajus
- Department of Industrial Engineering, University of Bologna, Forlì, Italy
| | - Giacomo Lari
- Department of Mathematics, University of Pisa, Pisa, Italy
| | - Marzia Parisi
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Dustin R Buccino
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Ryan S Park
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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Ingersoll AP. Cassini Exploration of the Planet Saturn: A Comprehensive Review. SPACE SCIENCE REVIEWS 2020; 216:122. [PMID: 35027776 PMCID: PMC8753610 DOI: 10.1007/s11214-020-00751-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 10/10/2020] [Indexed: 06/14/2023]
Abstract
Before Cassini, scientists viewed Saturn's unique features only from Earth and from three spacecraft flying by. During more than a decade orbiting the gas giant, Cassini studied the planet from its interior to the top of the atmosphere. It observed the changing seasons, provided up-close observations of Saturn's exotic storms and jet streams, and heard Saturn's lightning, which cannot be detected from Earth. During the Grand Finale orbits, it dove through the gap between the planet and its rings and gathered valuable data on Saturn's interior structure and rotation. Key discoveries and events include: watching the eruption of a planet-encircling storm, which is a 20- or 30-year event, detection of gravity perturbations from winds 9000 km below the tops of the clouds, demonstration that eddies are supplying energy to the zonal jets, which are remarkably steady over the 25-year interval since the Voyager encounters, re-discovery of the north polar hexagon after 25 years, determination of elemental abundance ratios He/H, C/H, N/H, P/H, and As/H, which are clues to planet formation and evolution, characterization of the semiannual oscillation of the equatorial stratosphere, documentation of the mysteriously high temperatures of the thermosphere outside the auroral zone, and seeing the strange intermittency of lightning, which typically ceases to exist on the planet between outbursts every 1-2 years. These results and results from the Jupiter flyby are all discussed in this review.
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Affiliation(s)
- Andrew P Ingersoll
- Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125, USA
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