1
|
Wang X, Li L, Jiang X, Fry PM, West RA, Nixon CA, Guan L, Karandana G TD, Albright R, Colwell JE, Guillot T, Hofstadter MD, Kenyon ME, Mallama A, Perez-Hoyos S, Sanchez-Lavega A, Simon AA, Wenkert D, Zhang X. Cassini spacecraft reveals global energy imbalance of saturn. Nat Commun 2024; 15:5045. [PMID: 38890296 PMCID: PMC11189510 DOI: 10.1038/s41467-024-48969-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 05/15/2024] [Indexed: 06/20/2024] Open
Abstract
The global energy budget is pivotal to understanding planetary evolution and climate behaviors. Assessing the energy budget of giant planets, particularly those with large seasonal cycles, however, remains a challenge without long-term observations. Evolution models of Saturn cannot explain its estimated Bond albedo and internal heat flux, mainly because previous estimates were based on limited observations. Here, we analyze the long-term observations recorded by the Cassini spacecraft and find notably higher Bond albedo (0.41 ± 0.02) and internal heat flux (2.84 ± 0.20 Wm-2) values than previous estimates. Furthermore, Saturn's global energy budget is not in a steady state and exhibits significant dynamical imbalances. The global radiant energy deficit at the top of the atmosphere, indicative of the planetary cooling of Saturn, reveals remarkable seasonal fluctuations with a magnitude of 16.0 ± 4.2%. Further analysis of the energy budget of the upper atmosphere including the internal heat suggests seasonal energy imbalances at both global and hemispheric scales, contributing to the development of giant convective storms on Saturn. Similar seasonal variabilities of planetary cooling and energy imbalance exist in other giant planets within and beyond the Solar System, a prospect currently overlooked in existing evolutional and atmospheric models.
Collapse
Affiliation(s)
- Xinyue Wang
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, 77004, USA
| | - Liming Li
- Department of Physics, University of Houston, Houston, TX, 77004, USA.
| | - Xun Jiang
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, 77004, USA
| | - Patrick M Fry
- Space Science and Engineering Center, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Robert A West
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Conor A Nixon
- NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - Larry Guan
- Department of Physics, University of Houston, Houston, TX, 77004, USA
| | - Thishan D Karandana G
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, 77004, USA
| | - Ronald Albright
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, 77004, USA
| | - Joshua E Colwell
- Department of Physics, University of Central Florida, Orlando, FL, 32816, USA
| | - Tristan Guillot
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, 06108, France
| | - Mark D Hofstadter
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Matthew E Kenyon
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Anthony Mallama
- Department of Mathematics and Statistics, University of Maryland, College Park, MD, 20742, USA
| | - Santiago Perez-Hoyos
- Departamento de Fisica Aplicada I, Escuela de Ingenieria UPV/EHU, Bilbao, 18013, Spain
| | | | - Amy A Simon
- NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - Daniel Wenkert
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
| | - Xi Zhang
- Department of Earth and Planetary Sciences, UCSC, Santa Cruz, CA, 95064, USA
| |
Collapse
|
2
|
Li C, de Pater I, Moeckel C, Sault RJ, Butler B, deBoer D, Zhang Z. Long-lasting, deep effect of Saturn's giant storms. SCIENCE ADVANCES 2023; 9:eadg9419. [PMID: 37566653 PMCID: PMC10421028 DOI: 10.1126/sciadv.adg9419] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 07/12/2023] [Indexed: 08/13/2023]
Abstract
Planetary-scale giant storms erupt on Saturn quasiperiodically. There have been at least six recorded occurrences of past eruptions, and the most recent one was in 2010, with its whole life span captured by the Cassini mission. In 2015, we used the Very Large Array to probe the deep response of Saturn's troposphere to the giant storms. In addition to the remnant effect of the storm in 2010, we have found long-lasting signatures of all mid-latitude giant storms, a mixture of equatorial storms up to hundreds of years old, and potentially an unreported older storm at 70°N. We derive an ammonia anomaly map that shows an extended meridional migration of the storm's aftermath and vertical transport of ammonia vapor by storm dynamics. Intriguingly, the last storm in 2010 splits into two distinct components that propagate in opposite meridional directions, leaving a gap at 43°N planetographic latitude.
Collapse
Affiliation(s)
- Cheng Li
- Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Imke de Pater
- Department of Astronomy, University of California, Berkeley, Berkeley, CA, USA
- Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA, USA
| | - Chris Moeckel
- Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA, USA
| | - R. J. Sault
- School of Physics, University of Melbourne, Victoria 3010, Australia
| | - Bryan Butler
- National Radio Astronomy Observatory, Socorro, NM, USA
| | - David deBoer
- Department of Astronomy, University of California, Berkeley, Berkeley, CA, USA
| | - Zhimeng Zhang
- Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| |
Collapse
|
3
|
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.
Collapse
Affiliation(s)
- Andrew P Ingersoll
- Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125, USA
| |
Collapse
|
4
|
Fletcher LN, Kaspi Y, Guillot T, Showman AP. How Well Do We Understand the Belt/Zone Circulation of Giant Planet Atmospheres? SPACE SCIENCE REVIEWS 2020; 216:30. [PMID: 32214508 PMCID: PMC7067733 DOI: 10.1007/s11214-019-0631-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 12/24/2019] [Indexed: 05/20/2023]
Abstract
The atmospheres of the four giant planets of our Solar System share a common and well-observed characteristic: they each display patterns of planetary banding, with regions of different temperatures, composition, aerosol properties and dynamics separated by strong meridional and vertical gradients in the zonal (i.e., east-west) winds. Remote sensing observations, from both visiting spacecraft and Earth-based astronomical facilities, have revealed the significant variation in environmental conditions from one band to the next. On Jupiter, the reflective white bands of low temperatures, elevated aerosol opacities, and enhancements of quasi-conserved chemical tracers are referred to as 'zones.' Conversely, the darker bands of warmer temperatures, depleted aerosols, and reductions of chemical tracers are known as 'belts.' On Saturn, we define cyclonic belts and anticyclonic zones via their temperature and wind characteristics, although their relation to Saturn's albedo is not as clear as on Jupiter. On distant Uranus and Neptune, the exact relationships between the banded albedo contrasts and the environmental properties is a topic of active study. This review is an attempt to reconcile the observed properties of belts and zones with (i) the meridional overturning inferred from the convergence of eddy angular momentum into the eastward zonal jets at the cloud level on Jupiter and Saturn and the prevalence of moist convective activity in belts; and (ii) the opposing meridional motions inferred from the upper tropospheric temperature structure, which implies decay and dissipation of the zonal jets with altitude above the clouds. These two scenarios suggest meridional circulations in opposing directions, the former suggesting upwelling in belts, the latter suggesting upwelling in zones. Numerical simulations successfully reproduce the former, whereas there is a wealth of observational evidence in support of the latter. This presents an unresolved paradox for our current understanding of the banded structure of giant planet atmospheres, that could be addressed via a multi-tiered vertical structure of "stacked circulation cells," with a natural transition from zonal jet pumping to dissipation as we move from the convectively-unstable mid-troposphere into the stably-stratified upper troposphere.
Collapse
Affiliation(s)
- Leigh N. Fletcher
- School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH UK
| | - Yohai Kaspi
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, 76100 Israel
| | - Tristan Guillot
- Université Côte d’Azur, OCA, Lagrange CNRS, 06304 Nice, France
| | - Adam P. Showman
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092 USA
| |
Collapse
|
5
|
Fletcher LN, Orton GS, Sinclair JA, Guerlet S, Read PL, Antuñano A, Achterberg RK, Flasar FM, Irwin PGJ, Bjoraker GL, Hurley J, Hesman BE, Segura M, Gorius N, Mamoutkine A, Calcutt SB. A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex. Nat Commun 2018; 9:3564. [PMID: 30177694 PMCID: PMC6120878 DOI: 10.1038/s41467-018-06017-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 08/01/2018] [Indexed: 11/30/2022] Open
Abstract
Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon-which was previously expected to be trapped in the troposphere-can influence the stratospheric temperatures some 300 km above Saturn's clouds.
Collapse
Affiliation(s)
- L N Fletcher
- Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK.
| | - G S Orton
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA
| | - J A Sinclair
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA
| | - S Guerlet
- Laboratoire de Meteorologie Dynamique/IPSL, Sorbonne Université, École Normale Supérieure, PSL Research University, École Polytechnique, CNRS, F-75005, Paris, France
| | - P L Read
- Department of Physics (Atmospheric, Oceanic and Planetary Physics), University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - A Antuñano
- Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | - R K Achterberg
- Department of Astronomy, University of Maryland, College Park, MD, 20742, USA
| | - F M Flasar
- NASA/Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - P G J Irwin
- Department of Physics (Atmospheric, Oceanic and Planetary Physics), University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - G L Bjoraker
- NASA/Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - J Hurley
- STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK
| | - B E Hesman
- Space Telescope Science Institute (STScI), 3700 San Martin Drive, Baltimore, MD, 21218, USA
| | - M Segura
- NASA/Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - N Gorius
- Department of Physics, The Catholic University of America, Washington, DC, 20064, USA
| | - A Mamoutkine
- NASA/Goddard Space Flight Center, Greenbelt, MD, 20771, USA
| | - S B Calcutt
- Department of Physics (Atmospheric, Oceanic and Planetary Physics), University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| |
Collapse
|
6
|
Fletcher LN, Melin H, Adriani A, Simon AA, Sanchez-Lavega A, Donnelly PT, Antuñano A, Orton GS, Hueso R, Kraaikamp E, Wong MH, Barnett M, Moriconi ML, Altieri F, Sindoni G. Jupiter's Mesoscale Waves Observed at 5 μm by Ground-based Observations and Juno JIRAM. THE ASTRONOMICAL JOURNAL 2018; 156:67. [PMID: 30510303 PMCID: PMC6267995 DOI: 10.3847/1538-3881/aace02] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We characterize the origin and evolution of a mesoscale wave pattern in Jupiter's North Equatorial Belt (NEB), detected for the first time at 5 μm using a 2016-17 campaign of "lucky imaging" from the VISIR instrument on the Very Large Telescope and the NIRI instrument on the Gemini observatory, coupled with M-band imaging from Juno's JIRAM instrument during the first seven Juno orbits. The wave is compact, with a 1°.1-1°.4 longitude wavelength (wavelength 1300-1600 km, wavenumber 260-330) that is stable over time, with wave crests aligned largely north-south between 14°N and 17°N (planetographic). The waves were initially identified in small (10° longitude) packets immediately west of cyclones in the NEB at 16°N but extended to span wider longitude ranges over time. The waves exhibit a 7-10 K brightness temperature amplitude on top of an ∼210 K background at 5 μm. The thermal structure of the NEB allows for both inertio-gravity waves and gravity waves. Despite detection at 5 μm, this does not necessarily imply a deep location for the waves, and an upper tropospheric aerosol layer near 400-800 mbar could feature a gravity wave pattern modulating the visible-light reflectivity and attenuating the 5-μm radiance originating from deeper levels. Strong rifting activity appears to obliterate the pattern, which can change on timescales of weeks. The NEB underwent a new expansion and contraction episode in 2016-17 with associated cyclone-anticyclone formation, which could explain why the mesoscale wave pattern was more vivid in 2017 than ever before.
Collapse
Affiliation(s)
- Leigh N Fletcher
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK;
| | - H Melin
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK;
| | - A Adriani
- INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - A A Simon
- NASA Goddard Space Flight Center Solar System Exploration Division (690) Greenbelt, MD 20771, USA
| | - A Sanchez-Lavega
- Departamento de Física Aplicada I, Escuela de Ingeniera de Bilbao, UPV/EHU, Plaza Ingeniero Torres Quevedo, 1, E-48013 Bilbao, Spain
| | - P T Donnelly
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK;
| | - A Antuñano
- Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK;
| | - G S Orton
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
| | - R Hueso
- Departamento de Física Aplicada I, Escuela de Ingeniera de Bilbao, UPV/EHU, Plaza Ingeniero Torres Quevedo, 1, E-48013 Bilbao, Spain
| | - E Kraaikamp
- Jourdanstraat 121/8, B-1060, Sint-Gillis, Belgium
| | - M H Wong
- University of California at Berkeley, Astronomy Department, Berkeley, CA 947200-3411, USA
| | - M Barnett
- University of California at Berkeley, Astronomy Department, Berkeley, CA 947200-3411, USA
| | - M L Moriconi
- CNR-Istituto di Scienze dell Atmosfera e del Clima, Bologna e Roma, Italy
| | - F Altieri
- INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| | - G Sindoni
- INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy
| |
Collapse
|
7
|
Sánchez-Lavega A, García-Melendo E, Pérez-Hoyos S, Hueso R, Wong MH, Simon A, Sanz-Requena JF, Antuñano A, Barrado-Izagirre N, Garate-Lopez I, Rojas JF, Del Río-Gaztelurrutia T, Gómez-Forrellad JM, de Pater I, Li L, Barry T. An enduring rapidly moving storm as a guide to Saturn's Equatorial jet's complex structure. Nat Commun 2016; 7:13262. [PMID: 27824031 PMCID: PMC5105178 DOI: 10.1038/ncomms13262] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 09/16/2016] [Indexed: 11/09/2022] Open
Abstract
Saturn has an intense and broad eastward equatorial jet with a complex three-dimensional structure mixed with time variability. The equatorial region experiences strong seasonal insolation variations enhanced by ring shadowing, and three of the six known giant planetary-scale storms have developed in it. These factors make Saturn's equator a natural laboratory to test models of jets in giant planets. Here we report on a bright equatorial atmospheric feature imaged in 2015 that moved steadily at a high speed of 450 ms-1 not measured since 1980-1981 with other equatorial clouds moving within an ample range of velocities. Radiative transfer models show that these motions occur at three altitude levels within the upper haze and clouds. We find that the peak of the jet (latitudes 10° N to 10° S) suffers intense vertical shears reaching +2.5 ms-1 km-1, two orders of magnitude higher than meridional shears, and temporal variability above 1 bar altitude level.
Collapse
Affiliation(s)
- A Sánchez-Lavega
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - E García-Melendo
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain.,Fundació Observatori Esteve Duran, c/ Montseny, 46-Urb. El Montanyá, Seva 08553, Barcelona, Spain
| | - S Pérez-Hoyos
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - R Hueso
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - M H Wong
- University of California, Department of Astronomy, 501 Campbell Hall, Berkeley, California 94720, USA
| | - A Simon
- NASA Goddard Space Flight Center/690, 8800 Greenbelt Road, Greenbelt, Maryland 20771, USA
| | - J F Sanz-Requena
- Universidad Europea Miguel de Cervantes, Departamento de Ciencias Experimentales, C/Padre Julio Chevalier, 2, 47012 Valladolid, Spain
| | - A Antuñano
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - N Barrado-Izagirre
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - I Garate-Lopez
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - J F Rojas
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - T Del Río-Gaztelurrutia
- Departamento Física Aplicada I, Universidad del País Vasco UPV/EHU, Escuela de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013 Bilbao, Spain
| | - J M Gómez-Forrellad
- Fundació Observatori Esteve Duran, c/ Montseny, 46-Urb. El Montanyá, Seva 08553, Barcelona, Spain
| | - I de Pater
- University of California, Department of Astronomy, 501 Campbell Hall, Berkeley, California 94720, USA
| | - L Li
- Department of Physics, University of Houston, Houston, Texas 77204, USA
| | - T Barry
- Broken Hill Observatory, 406 Bromide Street, Broken Hill, New South Wales 2880, Australia
| |
Collapse
|
8
|
Trammell HJ, Li L, Jiang X, Pan Y, Smith MA, Bering EA, Hörst SM, Vasavada AR, Ingersoll AP, Janssen MA, West RA, Porco CC, Li C, Simon AA, Baines KH. Vortices in Saturn's Northern Hemisphere (2008-2015) Observed by Cassini ISS. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2016; 121:1814-1826. [PMID: 29629249 PMCID: PMC5886353 DOI: 10.1002/2016je005122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We use observations from the Imaging Science Subsystem on Cassini to create maps of Saturn's Northern Hemisphere (NH) from 2008 to 2015, a time period including a seasonal transition (i.e., Spring Equinox in 2009) and the 2010 giant storm. The processed maps are used to investigate vortices in the NH during the period of 2008-2015. All recorded vortices have diameters (east-west) smaller than 6000 km except for the largest vortex that developed from the 2010 giant storm. The largest vortex decreased its diameter from ~11000 km in 2011 to ~5000 km in 2015, and its average diameter is ~6500 km during the period of 2011-2015. The largest vortex lasts at least 4 years, which is much longer than the lifetimes of most vortices (less than 1 year). The largest vortex drifts to north, which can be explained by the beta drift effect. The number of vortices displays varying behaviors in the meridional direction, in which the 2010 giant storm significantly affects the generation and development of vortices in the middle latitudes (25-45°N). In the higher latitudes (45-90°N), the number of vortices also displays strong temporal variations. The solar flux and the internal heat do not directly contribute to the vortex activities, leaving the temporal variations of vortices in the higher latitudes (45-90°N) unexplained.
Collapse
Affiliation(s)
- Harold Justin Trammell
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas, USA
| | - Liming Li
- Department of Physics, University of Houston, Houston, Texas, USA
| | - Xun Jiang
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas, USA
| | - Yefeng Pan
- Department of Physics, University of Houston, Houston, Texas, USA
| | - Mark A Smith
- Department of Chemistry, University of Houston, Houston, Texas, USA
| | - Edgar A Bering
- Department of Physics, University of Houston, Houston, Texas, USA
| | - Sarah M Hörst
- Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland, USA
| | - Ashwin R Vasavada
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Andrew P Ingersoll
- Division of Geological and Planetary Sciences, Caltech, Pasadena, California, USA
| | - Michael A Janssen
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Robert A West
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Carolyn C Porco
- Space Science and Engineering Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Cheng Li
- Division of Geological and Planetary Sciences, Caltech, Pasadena, California, USA
| | - Amy A Simon
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - Kevin H Baines
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| |
Collapse
|
9
|
Moses JI, Armstrong ES, Fletcher LN, Friedson AJ, Irwin PGJ, Sinclair JA, Hesman BE. Evolution of Stratospheric Chemistry in the Saturn Storm Beacon Region. ICARUS 2015; 261:149-168. [PMID: 30842685 PMCID: PMC6398963 DOI: 10.1016/j.icarus.2015.08.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The giant northern-hemisphere storm that erupted on Saturn in December 2010 triggered significant changes in stratospheric temperatures and species abundances that persisted for more than a year after the original outburst. The stratospheric regions affected by the storm have been nicknamed "beacons" due to their prominent infrared-emission signatures (Fletcher, L.N. et al. [2011]. Science 332, 1413). The two beacon regions that were present initially merged in April 2011 to form a single, large, anticyclonic vortex (Fletcher, L.N. et al. [2012]. Icarus 221, 560). We model the expected photochemical evolution of the stratospheric constituents in the beacons from the initial storm onset through the merger and on out to March 2012. The results are compared with longitudinally resolved Cassini/CIRS spectra from May 2011. If we ignore potential changes due to vertical winds within the beacon, we find that C2H2, C2H6, and C3H8 remain unaffected by the increased stratospheric temperatures in the beacon, the abundance of the shorter-lived CH3C2H decreases, and the abundance of C2H4 increases significantly due to the elevated temperatures, the latter most notably in a secondary mixing-ratio peak located near mbar pressures. The C4H2 abundance in the model decreases by a factor of a few in the 0.01-10 mbar region but has a significant increase in the 10-30 mbar region due to evaporation of the previously condensed phase. The column abundances of C6H6 and H2O above ~30 mbar also increase due to aerosol evaporation. Model-data comparisons show that models that consider temperature changes alone underpredict the abundance of C2H x species by a factor of 2-7 in the beacon core in May 2011, suggesting that other processes not considered by the models, such as downwelling winds in the vortex, are affecting the species profiles. Additional calculations indicate that downwelling winds of order -10 cm s -1 near ~0.1 mbar need to be included in the photochemical models in order to explain the inferred C2H x abundances in the beacon core, indicating that both strong subsiding winds and chemistry at elevated temperatures are affecting the vertical profiles of atmospheric constituents in the beacon. We (i) discuss the general chemical behavior of stratospheric species in the beacon region, (ii) demonstrate how the evolving beacon environment affects the species vertical profiles and emission characteristics (both with and without the presence of vertical winds), (iii) make predictions with respect to compositional changes that can be tested against Cassini and Herschel data, and higher-spectral-resolution ground-based observations of the beacon region, and (iv) discuss future measurements and modeling that could further our understanding of the dynamical origin, evolution, and chemical processing within these unexpected stratospheric vortices that were generated after the 2010 convective event.
Collapse
Affiliation(s)
- Julianne I Moses
- Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
| | - Eleanor S Armstrong
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | - Leigh N Fletcher
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | | | - Patrick G J Irwin
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | - James A Sinclair
- Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK
| | - Brigette E Hesman
- Department of Astronomy, University of Maryland, College Park, MD, 20742, USA
| |
Collapse
|
10
|
Li L, Achterberg RK, Conrath BJ, Gierasch PJ, Smith MA, Simon-Miller AA, Nixon CA, Orton GS, Flasar FM, Jiang X, Baines KH, Morales-Juberías R, Ingersoll AP, Vasavada AR, Del Genio AD, West RA, Ewald SP. Strong temporal variation over one Saturnian year: from Voyager to Cassini. Sci Rep 2013; 3:2410. [PMID: 23934437 PMCID: PMC3740281 DOI: 10.1038/srep02410] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 07/22/2013] [Indexed: 11/09/2022] Open
Abstract
Here we report the combined spacecraft observations of Saturn acquired over one Saturnian year (~29.5 Earth years), from the Voyager encounters (1980-81) to the new Cassini reconnaissance (2009-10). The combined observations reveal a strong temporal increase of tropic temperature (~10 Kelvins) around the tropopause of Saturn (i.e., 50 mbar), which is stronger than the seasonal variability (~a few Kelvins). We also provide the first estimate of the zonal winds at 750 mbar, which is close to the zonal winds at 2000 mbar. The quasi-consistency of zonal winds between these two levels provides observational support to a numerical suggestion inferring that the zonal winds at pressures greater than 500 mbar do not vary significantly with depth. Furthermore, the temporal variation of zonal winds decreases its magnitude with depth, implying that the relatively deep zonal winds are stable with time.
Collapse
Affiliation(s)
- Liming Li
- University of Houston, Houston, TX, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
|
12
|
Fischer G, Kurth WS, Gurnett DA, Zarka P, Dyudina UA, Ingersoll AP, Ewald SP, Porco CC, Wesley A, Go C, Delcroix M. A giant thunderstorm on Saturn. Nature 2011; 475:75-7. [DOI: 10.1038/nature10205] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 05/17/2011] [Indexed: 11/09/2022]
|