Steven D. Vance

Science potential from a Europa Lander

The prospect of a future soft landing on the surface of Europa is enticing, as it would create science opportunities that could not be achieved through flyby or orbital remote sensing, with direct relevance to Europas potential habitability. Here, we summarize the science of a Europa lander concept, as developed by our NASA-commissioned Science Definition Team. The science concept concentrates on observations that can best be achieved by in situ examination of Europa from its surface. We discuss the suggested science objectives and investigations for a Europa lander mission, along with a model planning payload of instruments that could address these objectives. The highest priority is active sampling of Europas non-ice material from at least two different depths (0.5-2u2009cm and 5-10u2009cm) to understand its detailed composition and chemistry and the specific nature of salts, any organic materials, and other contaminants. A secondary focus is geophysical prospecting of Europa, through seismology and magnetometry, to probe the satellites ice shell and ocean. Finally, the surface geology can be characterized in situ at a human scale. A Europa lander could take advantage of the complex radiation environment of the satellite, landing where modeling suggests that radiation is about an order of magnitude less intense than in other regions. However, to choose a landing site that is safe and would yield the maximum science return, thorough reconnaissance of Europa would be required prior to selecting a scientifically optimized landing site.

Geophysical controls of chemical disequilibria in Europa

The ocean in Jupiters moon Europa may have redox balance similar to Earths. On Earth, low-temperature hydration of crustal olivine produces substantial hydrogen, comparable to any potential flux from volcanic activity. Here we compare hydrogen and oxygen production rates of the Earth system with fluxes to Europas ocean. Even without volcanic hydrothermal activity, water-rock alteration in Europa causes hydrogen fluxes 10 times smaller than Earths. Europas ocean may have become reducing for a brief epoch, for example, after a thermal-orbital resonance ∼2xa0Gyr after accretion. Estimated oxidant flux to Europas ocean is comparable to estimated hydrogen fluxes. Europas ice delivers oxidants to its ocean at the upper end of these estimates if its ice is geologically active, as evidence of geologic activity and subduction implies.

Geophysical Investigations of Habitability in Ice‐Covered Ocean Worlds

Geophysical measurements can reveal the structure of icy ocean worlds and cycling of volatiles. The associated density, temperature, sound speed, and electrical conductivity of such worlds thus characterizes their habitability. To explore the variability and correlation of these parameters, and to provide tools for planning and data analyses, we develop 1-D calculations of internal structure, which use available constraints on the thermodynamics of aqueous MgSO

The influence of meridional ice transport on Europa's ocean stratification and heat content

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Seismic Wave Propagation in Icy Ocean Worlds

, NaCl (as seawater), and NH

Expected seismicity and the seismic noise environment of Europa

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Vital Signs: Seismology of Icy Ocean Worlds

, water ices, and silicate content. Limits in available thermodynamic data narrow the parameter space that can be explored: insufficient coverage in pressure, temperature, and composition for end-member salinities of MgSO

The NASA Roadmap to Ocean Worlds

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Bright prospects for radar detection of Europa’s ocean

and NaCl, and for relevant water ices; and a dearth of suitable data for aqueous mixtures of Na-Mg-Cl-SO

The Early History of Enceladus: Setting the Scene for Today's Activity

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