Decadal timescale variability of the Enceladus plumes inferred from Cassini images
The brightness of the Enceladus plumes varies with position in the satellite's eccentric orbit, with altitude above the surface, and with time from one year to the next. Hedman et al. (2013, hereinafter H13) were the first to report these variations. They used data from Cassini's Visible a...
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ftcaltechauth:oai:authors.library.caltech.edu:sgdee-c4q46 2024-06-23T07:56:52+00:00 Decadal timescale variability of the Enceladus plumes inferred from Cassini images Ingersoll, Andrew P. Ewald, Shawn P. 2017-01-15 https://doi.org/10.1016/j.icarus.2016.09.018 unknown Elsevier https://doi.org/10.1016/j.icarus.2018.11.003 https://doi.org/10.1016/j.icarus.2016.09.018 oai:authors.library.caltech.edu:sgdee-c4q46 eprintid:71743 resolverid:CaltechAUTHORS:20161104-102822857 info:eu-repo/semantics/openAccess Other Icarus, 282, 260-275, (2017-01-15) Enceladus Saturn satellites Satellites Atmospheres info:eu-repo/semantics/article 2017 ftcaltechauth https://doi.org/10.1016/j.icarus.2016.09.01810.1016/j.icarus.2018.11.003 2024-06-12T06:19:42Z The brightness of the Enceladus plumes varies with position in the satellite's eccentric orbit, with altitude above the surface, and with time from one year to the next. Hedman et al. (2013, hereinafter H13) were the first to report these variations. They used data from Cassini's Visible and Infrared Mapping Spectrometer (VIMS). Here we present brightness observations from Cassini's Imaging Science Subsystem (ISS), which has 40 times higher spatial resolution than VIMS. Our unit of measure is slab density, the total mass of particles in a horizontal slab per unit thickness of the slab. Using slab density is one approach to correcting for the variation of brightness with wavelength and scattering angle. Approaches differ mainly by a multiplicative scaling factor that depends on particle density, which is uncertain. All approaches lead to the same qualitative conclusions and agree with the conclusions from VIMS. We summarize our conclusions as follows: At all altitudes between 50 and 200 km, the corrected brightness is 4–5 times greater when Enceladus is farther from Saturn (near apocenter) than when it is closer (near pericenter). A secondary maximum occurs after pericenter and before apocenter. Corrected brightness vs. altitude is best described as a power law whose negative exponent is greatest in magnitude at apocenter, indicating a slower launch speed for the particles at apocenter than at other points in the orbit. Corrected brightness decreased by roughly a factor of two during much of the period 2005–2015. The last is our principal result, and we offer three hypotheses to explain it. One is a long-period tide—the decreasing phase of an 11-year cycle in orbital eccentricity; another is buildup of ice at the throats of the vents; and the third is seasonal change—the end of summer at the south pole. © 2016 Elsevier Inc. Received 30 January 2016; Revised 8 September 2016; Accepted 12 September 2016; Available online 22 September 2016. This work was supported by NASA partly through the Cassini ... Article in Journal/Newspaper South pole Caltech Authors (California Institute of Technology) South Pole |
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Enceladus Saturn satellites Satellites Atmospheres |
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Enceladus Saturn satellites Satellites Atmospheres Ingersoll, Andrew P. Ewald, Shawn P. Decadal timescale variability of the Enceladus plumes inferred from Cassini images |
topic_facet |
Enceladus Saturn satellites Satellites Atmospheres |
description |
The brightness of the Enceladus plumes varies with position in the satellite's eccentric orbit, with altitude above the surface, and with time from one year to the next. Hedman et al. (2013, hereinafter H13) were the first to report these variations. They used data from Cassini's Visible and Infrared Mapping Spectrometer (VIMS). Here we present brightness observations from Cassini's Imaging Science Subsystem (ISS), which has 40 times higher spatial resolution than VIMS. Our unit of measure is slab density, the total mass of particles in a horizontal slab per unit thickness of the slab. Using slab density is one approach to correcting for the variation of brightness with wavelength and scattering angle. Approaches differ mainly by a multiplicative scaling factor that depends on particle density, which is uncertain. All approaches lead to the same qualitative conclusions and agree with the conclusions from VIMS. We summarize our conclusions as follows: At all altitudes between 50 and 200 km, the corrected brightness is 4–5 times greater when Enceladus is farther from Saturn (near apocenter) than when it is closer (near pericenter). A secondary maximum occurs after pericenter and before apocenter. Corrected brightness vs. altitude is best described as a power law whose negative exponent is greatest in magnitude at apocenter, indicating a slower launch speed for the particles at apocenter than at other points in the orbit. Corrected brightness decreased by roughly a factor of two during much of the period 2005–2015. The last is our principal result, and we offer three hypotheses to explain it. One is a long-period tide—the decreasing phase of an 11-year cycle in orbital eccentricity; another is buildup of ice at the throats of the vents; and the third is seasonal change—the end of summer at the south pole. © 2016 Elsevier Inc. Received 30 January 2016; Revised 8 September 2016; Accepted 12 September 2016; Available online 22 September 2016. This work was supported by NASA partly through the Cassini ... |
format |
Article in Journal/Newspaper |
author |
Ingersoll, Andrew P. Ewald, Shawn P. |
author_facet |
Ingersoll, Andrew P. Ewald, Shawn P. |
author_sort |
Ingersoll, Andrew P. |
title |
Decadal timescale variability of the Enceladus plumes inferred from Cassini images |
title_short |
Decadal timescale variability of the Enceladus plumes inferred from Cassini images |
title_full |
Decadal timescale variability of the Enceladus plumes inferred from Cassini images |
title_fullStr |
Decadal timescale variability of the Enceladus plumes inferred from Cassini images |
title_full_unstemmed |
Decadal timescale variability of the Enceladus plumes inferred from Cassini images |
title_sort |
decadal timescale variability of the enceladus plumes inferred from cassini images |
publisher |
Elsevier |
publishDate |
2017 |
url |
https://doi.org/10.1016/j.icarus.2016.09.018 |
geographic |
South Pole |
geographic_facet |
South Pole |
genre |
South pole |
genre_facet |
South pole |
op_source |
Icarus, 282, 260-275, (2017-01-15) |
op_relation |
https://doi.org/10.1016/j.icarus.2018.11.003 https://doi.org/10.1016/j.icarus.2016.09.018 oai:authors.library.caltech.edu:sgdee-c4q46 eprintid:71743 resolverid:CaltechAUTHORS:20161104-102822857 |
op_rights |
info:eu-repo/semantics/openAccess Other |
op_doi |
https://doi.org/10.1016/j.icarus.2016.09.01810.1016/j.icarus.2018.11.003 |
_version_ |
1802650236052570112 |