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Laboratory Measurements and Simulations of NaCl(aq) Electrical Conductivity at Ocean World Conditions

Presentation #220.07 in the session Laboratory Investigations (Poster + Lightning Talk)

Published onOct 23, 2023
Laboratory Measurements and Simulations of NaCl(aq) Electrical Conductivity at Ocean World Conditions

The Europa Clipper mission, set to launch in 2024, is poised to investigate the composition of Europa’s putative subsurface ocean [1] through investigation of Europa’s induced magnetic field. The induced field data obtained from ~50 flybys of Europa may be inverted to identify the electrical conductivity and thickness of the salty subsurface ocean that is consistent with the magnetic measurements. Laboratory measurements relating conductivity and the concentration of candidate salts are essential to constrain possible models of Europa’s ocean composition [2]. To maximize the science return of the magnetometer investigation, a comprehensive and precise dataset of electrical conductivity at the high-pressure, low-temperature (HPLT) conditions relevant to the ocean of Europa and those of other icy moons is necessary [3]. There exist few datasets of electrical conductivity of aqueous solutions in the HPLT regime relevant to icy moons. We have conducted molecular dynamics simulations of the candidate ocean solution NaCl(aq) [4] at the most comprehensive HPLT range in the literature, at 246–307 K, 0–2000 MPa, and 2, 5, and 10 wt%. We are also preparing a laboratory high-pressure vessel based on [5] in which we will measure the electrical impedance of NaCl and other candidate solutions at HPLT conditions to high precision. Measurements are made using electrical impedance spectroscopy in a custom-built apparatus. Thus far we have made measurements at 1 bar at varying temperatures as needed to characterize the experimental apparatus and benchmark it to known values. We will report the current status of these efforts and discuss the role of these data in geophysical modeling. The datasets derived from our work form a critical component in geophysical forward models that relate ocean properties to the induced magnetic field at Europa, which will be inferred from the Europa Clipper Magnetometer data, to determine the range of possible europan ocean compositions and ultimately Europa’s capacity for habitability.

[1] Zimmer et al (2000), Icarus 147(2)

[2] Hand and Chyba (2007), Icarus 189(2).

[3] Vance et al (2021), JGR: Planets 126(2).

[4] Zolotov and Shock (2001), JGR: Planets 106(E12).

[5] Vance and Brown (2008), Rev Sci Inst 79(10).

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