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Kang W. Nonsynchronous rotation of icy moon ice shells: The thermal wind perspective. SCIENCE ADVANCES 2024; 10:eadk2277. [PMID: 38266084 DOI: 10.1126/sciadv.adk2277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 12/21/2023] [Indexed: 01/26/2024]
Abstract
The ice shells of icy satellites have been hypothesized to undergo nonsynchronous rotation (NSR) under the influence of tidal torques and/or ocean currents. In this work, the author proposes that the thermal wind relationship can be combined with geostrophic turbulence theory to predict ocean stress onto the ice shell inside the tangent cylinder. High-resolution numerical simulations validate the prediction within a factor of 2. For the prediction to be valid, the rotation effect must dominate (Rossby number < 1), and the upper ocean should be stratified. The latter can be achieved with sufficiently large ice thickness variations [the threshold for Europa is O(100) m]. Using this framework, once the ice rheology, thickness variations and NSR rate are determined, one may be able to estimate the ocean overturn timescale and put constraints on the ocean vertical diffusivity or the heat flux originating from the silicate core.
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Affiliation(s)
- Wanying Kang
- Earth, Atmospheric and Planetary Science Department, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA
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2
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Collins GC, Patterson GW, Detelich CE, Prockter LM, Kattenhorn SA, Cooper CM, Rhoden AR, Cutler BB, Oldrid SR, Perkins RP, Rezza CA. Episodic Plate Tectonics on Europa: Evidence for Widespread Patches of Mobile-Lid Behavior in the Antijovian Hemisphere. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2022; 127:e2022JE007492. [PMID: 37035521 PMCID: PMC10078521 DOI: 10.1029/2022je007492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/25/2022] [Accepted: 11/01/2022] [Indexed: 06/19/2023]
Abstract
A nearly pole-to-pole survey near 140°E longitude on Europa revealed many areas that exhibit past lateral surface motions, and these areas were examined to determine whether the motions can be described by systems of rigid plates moving across Europa's surface. Three areas showing plate-like behavior were examined in detail to determine the sequence of events that deformed the surface. All three areas were reconstructed to reveal the original pre-plate motion surfaces by performing multi-stage rotations of plates in spherical coordinates. Several motions observed along single plate boundaries were also noted in previous works, but this work links together isolated observations of lateral offsets into integrated systems of moving plates. Not all of the surveyed surface could be described by systems of rigid plates. There is evidence that the plate motions did not all happen at the same time, and that they are not happening today. We conclude that plate tectonic-like behavior on Europa occurs episodically, in limited regions, with less than 100 km of lateral motion accommodated along any particular boundary before plate motions cease. Europa may represent a world perched on the theoretical boundary between stagnant and mobile lid convective behavior, or it may represent an additional example of the wide variations in possible planetary convective regimes. Differences in observed strike-slip sense and plate rotation directions between the northern and southern hemispheres raise the question of whether tidal forces may influence plate motions.
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Affiliation(s)
| | | | - Charlene E. Detelich
- Johns Hopkins University Applied Physics LaboratoryLaurelMDUSA
- Now at Cornell UniversityIthacaNYUSA
| | | | | | | | | | | | | | - Reid P. Perkins
- Johns Hopkins University Applied Physics LaboratoryLaurelMDUSA
- Now at Western UniversityLondonONCanada
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Wolfenbarger NS, Buffo JJ, Soderlund KM, Blankenship DD. Ice Shell Structure and Composition of Ocean Worlds: Insights from Accreted Ice on Earth. ASTROBIOLOGY 2022; 22:937-961. [PMID: 35787145 DOI: 10.1089/ast.2021.0044] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Accreted ice retains and preserves traces of the ocean from which it formed. In this work, we study two classes of accreted ice found on Earth-frazil ice, which forms through crystallization within a supercooled water column, and congelation ice, which forms through directional freezing at an existing interface-and discuss where each might be found in the ice shells of ocean worlds. We focus our study on terrestrial ice formed in low temperature gradient environments (e.g., beneath ice shelves), consistent with conditions expected at the ice-ocean interfaces of Europa and Enceladus, and we highlight the juxtaposition of compositional trends in relation to ice formed in higher temperature gradient environments (e.g., at the ocean surface). Observations from Antarctic sub-ice-shelf congelation ice and marine ice show that the purity of frazil ice can be nearly two orders of magnitude higher than congelation ice formed in the same low temperature gradient environment (∼0.1% vs. ∼10% of the ocean salinity). In addition, where congelation ice can maintain a planar ice-water interface on a microstructural scale, the efficiency of salt rejection is enhanced (∼1% of the ocean salinity) and lattice soluble impurities such as chloride are preferentially incorporated. We conclude that an ice shell that forms by gradual thickening as its interior cools would be composed of congelation ice, whereas frazil ice will accumulate where the ice shell thins on local (rifts and basal fractures) or regional (latitudinal gradients) scales through the operation of an "ice pump."
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Affiliation(s)
| | - Jacob J Buffo
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Krista M Soderlund
- Institute for Geophysics, University of Texas at Austin, Austin, Texas, USA
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4
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Dalton JB, Shirley JH, Kamp LW. Europa's icy bright plains and dark linea: Exogenic and endogenic contributions to composition and surface properties. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011je003909] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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5
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True polar wander on Europa from global-scale small-circle depressions. Nature 2008; 453:368-71. [DOI: 10.1038/nature06911] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Accepted: 03/06/2008] [Indexed: 11/08/2022]
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6
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Panning M, Lekic V, Manga M, Cammarano F, Romanowicz B. Long-period seismology on Europa: 2. Predicted seismic response. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006je002712] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- M. Panning
- Berkeley Seismological Laboratory; University of California, Berkeley; Berkeley California USA
| | - V. Lekic
- Berkeley Seismological Laboratory; University of California, Berkeley; Berkeley California USA
| | - M. Manga
- Department of Earth and Planetary Science; University of California, Berkeley; Berkeley California USA
| | - F. Cammarano
- Berkeley Seismological Laboratory; University of California, Berkeley; Berkeley California USA
| | - B. Romanowicz
- Berkeley Seismological Laboratory; University of California, Berkeley; Berkeley California USA
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8
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Fagents SA. Considerations for effusive cryovolcanism on Europa: The post-Galileo perspective. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2003je002128] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sarah A. Fagents
- Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Sciences and Technology; University of Hawaii at Manoa; Honolulu Hawaii USA
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9
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Ice-volcanism due to tidal stress on Europa. CHINESE SCIENCE BULLETIN-CHINESE 2003. [DOI: 10.1007/bf03184185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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10
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Prockter LM. Morphology of Europan bands at high resolution: A mid-ocean ridge-type rift mechanism. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/2000je001458] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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11
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Schulze-Makuch D, Irwin LN. Energy cycling and hypothetical organisms in Europa's ocean. ASTROBIOLOGY 2002; 2:105-121. [PMID: 12449859 DOI: 10.1089/153110702753621385] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
While Europa has emerged as a leading candidate for harboring extraterrestrial life, the apparent lack of a source of free energy for sustaining living systems has been argued. In this theoretical analysis, we have quantified the amount of energy that could in principle be obtained from chemical cycling, heat, osmotic gradients, kinetic motion, magnetic fields, and gravity in Europa's subsurface ocean. Using reasonable assumptions based on known organisms on Earth, our calculations suggest that chemical oxidation-reduction cycles in Europa's subsurface ocean could support life. Osmotic and thermal gradients, as well as the kinetic energy of convection currents, also represent plausible alternative sources of energy for living systems at Europa. Organisms thriving on these gradients could interact with each other to form the complex energy cycling necessary for establishing a stable ecosystem.
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Affiliation(s)
- Dirk Schulze-Makuch
- Department of Geological Sciences, University of Texas at El Paso, El Paso, TX, USA.
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Khurana KK, Kivelson MG, Russell CT. Searching for liquid water in Europa by using surface observatories. ASTROBIOLOGY 2002; 2:93-103. [PMID: 12449858 DOI: 10.1089/153110702753621376] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Liquid water, as far as we know, is an indispensable ingredient of life. Therefore, locating reservoirs of liquid water in extraterrestrial bodies is a necessary prerequisite to searching for life. Recent geological and geophysical observations from the Galileo spacecraft, though not unambiguous, hint at the possibility of a subsurface ocean in the Jovian moon Europa. After summarizing present evidence for liquid water in Europa, we show that electromagnetic and seismic observations made from as few as two surface observatories comprising a magnetometer and a seismometer offer the best hope of unambiguous characterization of the three-dimensional structure of the ocean and the deeper interior of this icy moon. The observatories would also help us infer the composition of the icy crust and the ocean water.
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Affiliation(s)
- Krishan K Khurana
- Institute of Geophysics and Planetary Physics, University of California at Los Angeles, Los Angeles, CA, USA.
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Abstract
Several impact craters on Jupiter's satellite Europa exhibit central peaks. On the terrestrial planets, central peaks consist of fractured but competent rock uplifted during cratering. Therefore, the observation of central peaks on Europa indicates that an ice layer must be sufficiently thick that the impact events did not completely penetrate it. We conducted numerical simulations of vapor and melt production during cratering of water ice layers overlying liquid water to estimate the thickness of Europa's icy crust. Because impacts disrupt material well beyond the zone of partial melting, our simulations put a lower limit on ice thickness at the locations and times of impact. We conclude that the ice must be more than 3 to 4 kilometers thick.
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Affiliation(s)
- E P Turtle
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
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Fanale FP, Li YH, De Carlo E, Farley C, Sharma SK, Horton K, Granahan JC. An experimental estimate of Europa's “ocean” composition independent of Galileo orbital remote sensing. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000je001385] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Chyba C, Phillips C. Possible ecosystems and the search for life on Europa. Proc Natl Acad Sci U S A 2001; 98:801-4. [PMID: 11158549 PMCID: PMC33371 DOI: 10.1073/pnas.98.3.801] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- C Chyba
- Center for the Study of Life in the Universe, SETI Institute, Mountain View, CA 94043, USA.
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Abstract
As the field of astrobiology matures and search strategies for life on other worlds are developed, the need to analyze in a systematic way the plausibility for life on other planetary systems becomes increasingly apparent. We propose the adoption of a simple plausibility of life (POL) rating system based on specific criteria. Category I applies to any body shown to have conditions essentially equivalent to those on Earth. Category II applies to bodies for which there is evidence of liquid water and sources of energy and where organic compounds have been detected or can reasonably be inferred (Mars, Europa). Category III applies to worlds where conditions are physically extreme but possibly capable of supporting exotic forms of life unknown on Earth (Titan, Triton). Category IV applies to bodies that could have seen the origin of life prior to the development of conditions so harsh as to make its perseverance at present unlikely but conceivable in isolated habitats (Venus, Io). Category V would be reserved for sites where conditions are so unfavorable for life by any reasonable definition that its origin or persistence there cannot be rated a realistic probability (the Sun, gas giant planets). The proposed system is intended to be generic. It assumes that life is based on polymeric chemistry occurring in a liquid medium with uptake and degradation of energy from the environment. Without any additional specific assumptions about the nature of life, the POL system is universally applicable.
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Affiliation(s)
- L N Irwin
- Department of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968, USA.
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Kadel SD, Chuang FC, Greeley R, Moore JM. Geological history of the Tyre region of Europa: A regional perspective on Europan surface features and ice thickness. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001203] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Riley J, Hoppa GV, Greenberg R, Tufts BR, Geissler P. Distribution of chaotic terrain on Europa. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001164] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Greeley R, Figueredo PH, Williams DA, Chuang FC, Klemaszewski JE, Kadel SD, Prockter LM, Pappalardo RT, Head JW, Collins GC, Spaun NA, Sullivan RJ, Moore JM, Senske DA, Tufts BR, Johnson TV, Belton MJS, Tanaka KL. Geologic mapping of Europa. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001173] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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20
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Figueredo PH, Greeley R. Geologic mapping of the northern leading hemisphere of Europa from Galileo solid-state imaging data. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001107] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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21
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Greenberg R, Geissler P, Tufts BR, Hoppa GV. Habitability of Europa's crust: The role of tidal-tectonic processes. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001147] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Head JW, Pappalardo RT, Sullivan R. Europa: Morphological characteristics of ridges and triple bands from Galileo data (E4 and E6) and assessment of a linear diapirism model. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998je001011] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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23
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Pappalardo RT, Belton MJS, Breneman HH, Carr MH, Chapman CR, Collins GC, Denk T, Fagents S, Geissler PE, Giese B, Greeley R, Greenberg R, Head JW, Helfenstein P, Hoppa G, Kadel SD, Klaasen KP, Klemaszewski JE, Magee K, McEwen AS, Moore JM, Moore WB, Neukum G, Phillips CB, Prockter LM, Schubert G, Senske DA, Sullivan RJ, Tufts BR, Turtle EP, Wagner R, Williams KK. Does Europa have a subsurface ocean? Evaluation of the geological evidence. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998je000628] [Citation(s) in RCA: 304] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
NASA's Galileo mission to Jupiter and improved Earth-based observing capabilities have allowed major advances in our understanding of Jupiter's moons Io, Europa, Ganymede, and Callisto over the past few years. Particularly exciting findings include the evidence for internal liquid water oceans in Callisto and Europa, detection of a strong intrinsic magnetic field within Ganymede, discovery of high-temperature silicate volcanism on Io, discovery of tenuous oxygen atmospheres at Europa and Ganymede and a tenuous carbon dioxide atmosphere at Callisto, and detection of condensed oxygen on Ganymede. Modeling of landforms seen at resolutions up to 100 times as high as those of Voyager supports the suggestion that tidal heating has played an important role for Io and Europa.
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Affiliation(s)
- A P Showman
- Department of Mechanical Engineering, University of Louisville, 215 Sackett Hall, Louisville, KY 40292, USA
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25
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Prockter LM, Antman AM, Pappalardo RT, Head JW, Collins GC. Europa: Stratigraphy and geological history of the anti-Jovian region from Galileo E14 solid-state imaging data. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1998je001015] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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Abstract
We exploit recent theoretical advances toward the origin and orbital evolution of comets and asteroids to obtain revised estimates for cratering rates in the jovian system. We find that most, probably more than 90%, of the craters on the Galilean satellites are caused by the impact of Jupiter-family comets (JFCs). These are comets with short periods, in generally low-inclination orbits, whose dynamics are dominated by Jupiter. Nearly isotropic comets (long period and Halley-type) contribute at the 1-10% level. Trojan asteroids might also be important at the 1-10% level; if they are important, they would be especially important for smaller craters. Main belt asteroids are currently unimportant, as each 20-km crater made on Ganymede implies the disruption of a 200-km diameter parental asteroid, a destruction rate far beyond the resources of today's asteroid belt. Twenty-kilometer diameter craters are made by kilometer-size impactors; such events occur on a Galilean satellite about once in a million years. The paucity of 20-km craters on Europa indicates that its surface is of order 10 Ma. Lightly cratered surfaces on Ganymede are nominally of order 0.5-1.0 Ga. The uncertainty in these estimates is about a factor of five. Callisto is old, probably more than 4 Ga. It is too heavily cratered to be accounted for by the current flux of JFCs. The lack of pronounced apex-antapex asymmetries on Ganymede may be compatible with crater equilibrium, but it is more easily understood as evidence for nonsynchronous rotation of an icy carapace.
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Affiliation(s)
- K Zahnle
- NASA Ames Research Center, Moffett Field, California 94035, USA.
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27
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Naganuma T, Uematsu H. Dive Europa: a search-for-life initiative. UCHU SEIBUTSU KAGAKU 1998; 12:126-30. [PMID: 11541880 DOI: 10.2187/bss.12.126] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Liquid water, underwater volcanoes and possibly life forms have been suggested to be present beneath the estimated 10 km-thick ice shell of Europa the Jovian satellite J2. Europa's possible ocean is estimated to be 100-200km deep. Despite the great depth of the Europa's ocean, hydrostatic pressure at the seafloor would be 130-260 MPa, corresponding to 13-26 km depth of a theoretical Earth's ocean. The hydrostatic pressure is not beyond the edge of existing deep-sea technology. Here we propose exploration of Europa's deep-sea by the use of current technologies, taking a symbolic example of a deep submergence vehicle Shinkai 6500 which dives to a depth of 6.5 km deep (50 km depth of Europa's ocean). Shinkai 6500 is embarkable in the payload bay of the Space Shuttles in terms of size and weight for the transportation to a Low Earth Orbit (LEO). Secondary boost is needed for interplanetary flight from the LEO. On-orbit assembly of the secondary booster is a technological challenge. The International Space Station (ISS) and ISS-related technologies will facilitate the secondary boost. Also, ice shell drilling is a challenge and is needed before the dive into Europa's ocean. These challenges should be overcome during a certain leading time for matured experience in the ISS operation.
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Affiliation(s)
- T Naganuma
- Faculty of Applied Biological Science, Hiroshima University, Higashi-hiroshima, Japan.
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28
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Pappalardo RT, Head JW, Greeley R, Sullivan RJ, Pilcher C, Schubert G, Moore WB, Carr MH, Moore JM, Belton MJ, Goldsby DL. Geological evidence for solid-state convection in Europa's ice shell. Nature 1998; 391:365-8. [PMID: 9450750 DOI: 10.1038/34862] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean. Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively.
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Affiliation(s)
- R T Pappalardo
- Department of Geological Sciences, Brown University, Providence, Rhode Island 02912-1846, USA.
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