Entrainment and dynamics of ocean-derived impurities within Europa's ice shell

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Planets 125(10),(2020): e2020JE006394, doi:10.1029/2020JE006394.Compositional heterogeneities within Europa's ice shell likely impact the dynamics and habitability of the ice and subsurface ocean, but the total inventory and distribution of impurities within the shell are unknown. In sea ice on Earth, the thermochemical environment at the ice‐ocean interface governs impurity entrainment into the ice. Here, we simulate Europa's ice‐ocean interface and bound the impurity load (1.053–14.72 g/kg [parts per thousand weight percent, or ppt] bulk ice shell salinity) and bulk salinity profile of the ice shell. We derive constitutive equations that predict ice composition as a function of the ice shell thermal gradient and ocean composition. We show that evolving solidification rates of the ocean and hydrologic features within the shell produce compositional variations (ice bulk salinities of 5–50% of the ocean salinity) that can affect the material properties of the ice. As the shell thickens, less salt is entrained at the ice‐ocean interface, which implies Europa's ice shell is compositionally homogeneous below ~1 km. Conversely, the solidification of water filled fractures or lenses introduces substantial compositional variations within the ice shell, creating gradients in mechanical and thermal properties within the ice shell that could help initiate and sustain geological activity. Our results suggest that ocean materials entrained within Europa's ice shell affect the formation of geologic terrain and that these structures could be confirmed by planned spacecraft observations.This study was supported by the NASA Earth and Space Science Fellowship, grants NNX16AP43H S01 and NNX16AP43H S002. Britney Schmidt was additionally supported by the Europa Clipper Mission. Resources supporting this work were provided by the NASA High‐End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center.2021-03-2

Advances in planetary geology, volume 2

This publication is a continuation of volume 1; it is a compilation of reports focusing on research into the origin and evolution of the solar system with emphasis on planetary geology. Specific reports include a multispectral and geomorphic investigation of the surface of Europa and a geologic interpretation of remote sensing data for the Martian volcano Ascreaus Mons

Directory of research projects, 1991. Planetary geology and geophysics program

Information is provided about currently funded scientific research within the Planetary Geology and Geophysics Program. The directory consists of the proposal summary sheet from each proposal funded by the program during fiscal year 1991. Information is provided on the research topic, principal investigator, institution, summary of research objectives, past accomplishments, and proposed investigators

Part 1: Aspects of lithospheric evolution on Venus. Part 2: Thermal and collisional histories of chondrite parent bodies

The geological evolution of distinctly different kinds of solar system objects is addressed. Venus has been observed over the past decade by orbital radars on both American and Soviet spacecraft. These surface measurements provide clues to the structure and evolution of the lithosphere. The parent bodies of chondritic meteorites, thought to resemble asteroids, represent the other end of the size spectrum of terrestrial objects. Their early thermal and collisional histories may be constrained by the chemical and textural record preserved in meteorite samples. Impact craters on Venus have been observed by the Soviet Venera 15/16 spacecraft. A formalism is presented by which the size-frequency distribution of impact craters may be used to estimate upper bounds on the mean global rates of volcanic resurfacing and lithospheric recycling on that planet over the past several hundred million years. The impact crater density reported from Venera observations, if valid for the entire Venus surface, indicates a mean volcanic flux no greater than 2 cu km/y, corresponding to a maximum average rate of resurfacing of about 4 km/b.y. For the lowest estimated mean crater retention age of the surface of Venus imaged by Venera 15/16, the rate of lithospheric recycling on Venus does not exceed 1.5 sq km/y. Ordinary chondrite meteorites show textural and chemical patterns indicative of varying intensities of thermal metamorphism. The conventional onion-shell model, which envisions highly metamorphosed material in the core and less intensely heated rocks near the surface, predicts an inverse relation between peak temperature and cooking rate, but none has been observed. A metamorphosed-planetesimal model is devised to explain this discrepancy, whereby heating occurs in planetesimals a few kilometers in radius which then accrete to form 100-km-radius parent bodies. Cooling rates are then randomly controlled by burial depth. Thermal and collisional constraints are examined, and the model is found to be applicable only to highly insulating Al-26-rich planetesimals that remain closely aggregated upon accretion. An alternative model is presented, in which onion-shell parent bodies are collisionally fragmented during metamorphism and then gravitationally reassembled. If reassembly times are short, then cooling rates would be determined by burial depth in the reaccreted parent body. This model, unlike previous ones, can explain both coherent and incoherent cooling of Breccia clasts by collisions during or after metamorphism, respectively

I. Aspects of lithospheric evolution on Venus. ; II. Thermal and collisional histories of chondrite parent bodies

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Includes bibliographical references.by Robert E. Grimm.Ph.D

Directory of research projects: Planetary geology and geophysics program

Information about currently funded scientific research within the Planetary Geology and Geophysics Program is provided, including the proposal summary sheet from each proposal funded under the program during fiscal year 1990. Information about the research project, including title, principal investigator, institution, summary of research objectives, past accomplishments, and proposed new investigations is also provided

The Science of Solar System Ices (ScSSI) : a cross-disciplinary workshop, May 5-8, 2008, Oxnard, California

As a response to the growing need for cross-disciplinary dialog and communication in the Planetary Ices science community, NASA’s Jet Propulsion Laboratory and the Lunar and Planetary Institute are hosting a workshop entitled The Science of Solar System Ices (ScSSI): A Cross-Disciplinary Workshop. The role of laboratory research and simulations in advancing our understanding of solar system ices (including satellites, KBOs, comets, and giant planets) is becoming increasingly important. Understanding ice surface radiation processing, particle and radiation penetration depths, surface and subsurface chemistry, morphology, phases, density, conductivity, etc., are only a few examples of the inventory of issues that are being addressed by Earth-based laboratory research. This workshop aims to achieve direct dialog and foster focused collaborations among the observational, modeling, and laboratory research communities.Lunar and Planetary Institute, Jet Propulsion Laboratory, California Institute of Technology, National Aeronautics and Space Administration, Ball Aerospace and Technologies Corporation, Kurt J. Lesker Company, Thermo Fisher Scientific, Varian Incorporatedorganizers, Murthy Gudipati, Bob Pappalardo, Julie CastilloPARTIAL CONTENTS: Sublimation, Depostion and UV Photochemistry of Enceladus Plume Mixtures--The Roles of Energy Localization and Buried Interfaces in Electronic Sputtering of Pristine and Mixed Low-Temperature Ices--Spectroscopic Remote Sensing of Solar System Ices: Laboratory Research and Applications for Mapping Compounds--Ice Properties Relevant to Radar Sounding of Icy Moons: Lessons from Earth Applied to Europa

Workshop on Ices, Oceans, and Fire : Satellites of the Outer Solar System, August 13-15, 2007, Boulder, Colorado

The purpose of this workshop is to bring together researchers focused on specific satellites or mechanisms to share their work in the broader context of common processes and unique properties shaping the satellites of the outer solar system.sponsors, Lunar and Planetary Institute, National Aeronautics and Space Administrationconvener, Curt NieburPARTIAL CONTENTS: The Impact of Cratering in the Outer Solar System / P.M. Schenk -- Aurora on Ganymede / M.A. McGrath -- The Role of Tides in Tectonic Formation and Eruption Activity on Satellites in the Outer Solar System / T. Hurford -- Modeling Europa's Surface Composition with Cryogenic Sulfate Hydrates / J.B. Dalton III -- The Convective Dynamics of Icy Satellites and Implications for Surface Evolution / A. Showman

Reports of planetary geology and geophysics program, 1989

Abstracts of reports from Principal Investigators of NASA's Planetary Geology and Geophysics Program are compiled. The research conducted under this program during 1989 is summarized. Each report includes significant accomplishments in the area of the author's funded grant or contract