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Geosciences
Special Issues
Interiors of Icy Ocean Worlds
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Interiors of Icy Ocean Worlds

A special issue of Geosciences (ISSN 2076-3263).

Deadline for manuscript submissions: closed (7 June 2019) | Viewed by 16187

Special Issue Editor

Dr. Steven D. Vance

E-Mail Website
Guest Editor
Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Interests: ocean worlds; geophysics; astrobiology; missions

Special Issue Information

Dear Colleagues,

We are soliciting contributions for a Special Issue devoted to "Interiors of Icy Ocean Worlds". In recent decades, robotic missions have returned evidence of liquid water oceans on Jupiter's icy moons Europa, Ganymede, and Callisto, and in Saturn's moons Enceladus, Titan, and possibly Mimas and Dione. The icy moons of Uranus and Neptune—especially Triton—may also have oceans. Extinct or remnant oceans seem likely on the dwarf planets Ceres and Pluto. Oceanic worlds provide the best analogues in our solar system to a class of likely water-rich "super Earth" exoplanets. Geophysical measurements by future robotic missions can reveal the compositional and rheological structures and the thermal states of icy ocean worlds. The interior density, temperature, sound speed, and electrical conductivity thus characterize their habitability. In recent years, improvements in computational capabilities have enabled new insights into the interiors of icy ocean worlds, including the geodynamics of their icy lithospheres, coupled thermal and orbital evolution, and the flow of fluids in their oceans. Future spacecraft measurements require the further development of computational techniques for forward models and the inversion of data sets. Laboratory studies of material properties, chemistry, and spectral characteristics are needed in the large domain of pressure, temperature, and composition. This Special Issue solicits theoretical, numerical, and laboratory studies advancing our ability to acquire and interpret vital information about the interiors of icy ocean worlds.

Dr. Steven D. Vance
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Geosciences is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ocean worlds
  • geophysics
  • astrobiology
  • laboratory studies
  • missions

Published Papers (4 papers)

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Research

11 pages, 5525 KiB  
Article
Asymmetric Craters on the Dwarf Planet Ceres—Results of Second Extended Mission Data Analysis
by Katrin Krohn, Ralf Jaumann, Kai Wickhusen, Katharina A. Otto, Elke Kersten, Katrin Stephan, Roland J. Wagner, Carol A. Raymond and Christopher T. Russell
Geosciences 2019, 9(11), 475; https://doi.org/10.3390/geosciences9110475 - 12 Nov 2019
Cited by 2 | Viewed by 3234
Abstract
After almost three years of successful operation on Ceres, the Dawn spacecraft entered its last orbits around the dwarf planet and obtained a set of high-resolution images of 3 to 5 m/pixel. These images reveal a variety of morphologic features, including a set [...] Read more.
After almost three years of successful operation on Ceres, the Dawn spacecraft entered its last orbits around the dwarf planet and obtained a set of high-resolution images of 3 to 5 m/pixel. These images reveal a variety of morphologic features, including a set of asymmetric crater morphologies as observed earlier in the mission on the asteroid Vesta. We identified 269 craters, which are located between 60° N to 60° S latitude and 197° E to 265° E longitude, and investigated their morphological characteristics using a digital terrain model (DTM). These craters range in diameter from 0.30 to 4.2 km, and exhibit a sharp crater rim on the uphill side and a smooth one on the downhill side. We found that all asymmetric craters are formed on a sloping surface with the majority appearing at slope angles between 5 and 20 degrees. This implies that, as observed on Vesta, the topography is the main cause for these asymmetries. Full article
(This article belongs to the Special Issue Interiors of Icy Ocean Worlds)
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16 pages, 1970 KiB  
Article
Acoustic and Microstructural Properties of Partially Molten Samples in the Ice–Ammonia System
by Christine McCarthy, Michael A. Nielson, Allie N. Coonin, Jessica Shea Minker and Armando A. Domingos
Geosciences 2019, 9(8), 327; https://doi.org/10.3390/geosciences9080327 - 25 Jul 2019
Cited by 3 | Viewed by 2832
Abstract
We measured the ultrasonic properties and microstructure of two-phase binary mixtures of the ice–ammonia partial melt system, which was selected based on its importance for numerous planetary bodies. The equilibrium microstructure of ice–ammonia melt was examined using a light microscope within a cold [...] Read more.
We measured the ultrasonic properties and microstructure of two-phase binary mixtures of the ice–ammonia partial melt system, which was selected based on its importance for numerous planetary bodies. The equilibrium microstructure of ice–ammonia melt was examined using a light microscope within a cold room. The measured median dihedral angle between the solid and melt at 256 K is approximately 63°, with a broad distribution of observed angles between 10° and 130°. P-wave velocities in the partially molten samples were measured as a function of temperature (177 < T(K) < 268) and composition (1–6.4 wt % NH3). Vp decreases approximately linearly with increasing temperature and melt fraction. We compare the results of this study to those of other potential binary systems by normalizing the datasets using a vertical lever (TL–TE) and articulating the potential effects on the mechanical behavior and transport capabilities of partially molten ice in icy satellites. Full article
(This article belongs to the Special Issue Interiors of Icy Ocean Worlds)
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15 pages, 3586 KiB  
Article
Measuring Ganymede’s Librations with Laser Altimetry
by Gregor Steinbrügge, Teresa Steinke, Robin Thor, Alexander Stark and Hauke Hussmann
Geosciences 2019, 9(7), 320; https://doi.org/10.3390/geosciences9070320 - 20 Jul 2019
Cited by 9 | Viewed by 4026
Abstract
Jupiter’s moon Ganymede might be in possession of a subsurface ocean located between two ice layers. However, from Galileo data it is not possible to unambiguously infer the thickness and densities of the individual layers. The upcoming icy satellite mission JUICE (JUpiter ICy [...] Read more.
Jupiter’s moon Ganymede might be in possession of a subsurface ocean located between two ice layers. However, from Galileo data it is not possible to unambiguously infer the thickness and densities of the individual layers. The upcoming icy satellite mission JUICE (JUpiter ICy moons Explorer) will have the possibility to perform more detailed investigations of Ganymede’s interior structure with the radio science experiment 3GM and the GAnymede Laser Altimeter (GALA). Here we investigate the possibility to derive the rotational state of the outer ice shell by using topography measured by laser altimetry. We discuss two different methods to invert synthetic laser altimetry data. Method 1 is based on a spherical harmonics expansion and Method 2 solves for B-splines on a rectangular grid. While Method 1 has significant limitations due to the omission of high degrees of the global expansion, Method 2 leads to stable results allowing for an estimate of the in-orbit measurement accuracy. We estimate that GALA can measure the amplitude of Ganymede’s librations with an accuracy of 2.5–6.6 μ rad (6.6–17.4 m at the equator). This allows for determining the thickness of an elastic ice shell, if decoupled from the deeper interior by a subsurface ocean, to about an accuracy of 24–65 km. Full article
(This article belongs to the Special Issue Interiors of Icy Ocean Worlds)
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22 pages, 7005 KiB  
Article
High Pressure Hydrocarbons Revisited: From van der Waals Compounds to Diamond
by Lewis J. Conway and Andreas Hermann
Geosciences 2019, 9(5), 227; https://doi.org/10.3390/geosciences9050227 - 16 May 2019
Cited by 18 | Viewed by 5635
Abstract
Methane and other hydrocarbons are major components of the mantle regions of icy planets. Several recent computational studies have investigated the high-pressure behaviour of specific hydrocarbons. To develop a global picture of hydrocarbon stability, to identify relevant decomposition reactions, and probe eventual formation [...] Read more.
Methane and other hydrocarbons are major components of the mantle regions of icy planets. Several recent computational studies have investigated the high-pressure behaviour of specific hydrocarbons. To develop a global picture of hydrocarbon stability, to identify relevant decomposition reactions, and probe eventual formation of diamond, a complete study of all hydrocarbons is needed. Using density functional theory calculations we survey here all known C-H crystal structures augmented by targeted crystal structure searches to build hydrocarbon phase diagrams in the ground state and at elevated temperatures. We find that an updated pressure-temperature phase diagram for methane is dominated at intermediate pressures by CH 4 :H 2 van der Waals inclusion compounds. We discuss the P-T phase diagram for CH and CH 2 (i.e., polystyrene and polyethylene) to illustrate that diamond formation conditions are strongly composition dependent. Finally, crystal structure searches uncover a new CH 4 (H 2 ) 2 van der Waals compound, the most hydrogen-rich hydrocarbon, stable between 170 and 220 GPa. Full article
(This article belongs to the Special Issue Interiors of Icy Ocean Worlds)
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