Single‐ and Multi‐Pass Magnetometric Subsurface Ocean Detection and Characterization in Icy Worlds Using Principal Component Analysis (PCA): Application to Triton

Cochrane, Corey J.; Persinger, Randy R.; Vance, S.; Midkiff, E. L.; Castillo‐Rogez, Julie; Luspay‐Kuti, A.; Liuzzo, Lucas; Paty, C. S.; Mitchell, K. L.; Prockter, L. M.

doi:10.1029/2021ea002034

Cited by 15 publications

(14 citation statements)

References 49 publications

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“…Near the moons of Jupiter and Saturn, the ambient plasma flow is nearly always perpendicular to the direction of the magnetospheric background field. Near Neptune's moon Triton, the local magnetospheric field is never tilted by more than 43° against the direction of corotation (Cochrane et al., 2022; Liuzzo, Paty, et al., 2021). In comparison, the ambient plasma flow near Earth's Moon when located within a lobe of the terrestrial magnetotail is almost entirely aligned with the direction of the tail field.…”

Section: Discussionmentioning

confidence: 99%

A Statistical Study of the Moon's Magnetotail Plasma Environment

2022

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This study investigates the lunar plasma environment when embedded within Earth's magnetotail. We use data from 10 years of tail crossings by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) spacecraft in orbit around the Moon. We separate the plasma environments by magnetosheath‐like, magnetotail lobe‐like, and plasma sheet‐like conditions. Our findings highlight that the lobe‐like plasma is associated with low densities and a strong magnetic field, while the plasma sheet is characterized by higher densities and a weaker magnetic field. These regions are flanked by the fast, predominantly tailward flows of the terrestrial magnetosheath. During a single lunar crossing, however, the magnetotail displays a wide range of variability, with transient features—including reconnection events—intermixed between periods of lobe‐like or sheet‐like conditions. We compare and contrast the Moon's local magnetotail plasma to the environments near various outer‐planet moons. In doing so, we find that properties of the ambient lunar plasma are, at times, unique to the terrestrial magnetotail, while at others, may resemble those near the Jovian, Saturnian, and Neptunian moons. These findings highlight the complementary role of the ARTEMIS mission in providing a deeper understanding of the plasma interactions of the outer‐planet moons.

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Section: Discussionmentioning

confidence: 99%

A Statistical Study of the Moon's Magnetotail Plasma Environment

2022

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“…If the ocean is well mixed, the non-ice solids are distributed throughout the liquid similarly to the well-mixed chamber case, with the exception of the presence of a rocky core surrounded by the ocean. The 1-10 S m −1 conductivities of the partially frozen solutions considered here (Figures 5 and 7) suggest that global partially frozen oceans with these compositions would be detectable with existing remote magnetometry sensing at, e.g., the moons of ice giants (Cochrane et al 2021(Cochrane et al , 2022Castillo-Rogez et al 2023), even without considering additional contributions to solution conductivities from nitrogen-bearing species (Castillo-Rogez et al…”

Section: Applications To Cylindrical Crack and Global-scale Ocean Fre...mentioning

confidence: 69%

Salt Distribution from Freezing Intrusions in Ice Shells on Ocean Worlds: Application to Europa

Naseem,

Neveu,

Howell

et al. 2023

Planet. Sci. J.

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Several icy moons and dwarf planets appear to have hosted subsurface liquid water. Liquid water intruding upwards into the icy outer shells of these worlds freezes, forming ice and (from ocean solutes) non-ice solids. Here, we model concentrated aqueous solutions below 273 K to simulate the compositional evolution of freezing spherical intrusions. Starting solutions are based on five previously reported compositional end members for Europa’s ocean. For moderate-pH end members dominated by chloride, sulfate, and/or carbonate, the solids formed include Ca-, Mg-, and Na-sulfates and -carbonates, as well as Na- and K-chlorides. For silica-rich, high-pH end members, abundant amorphous silica forms with, potentially, similarly abundant NaOH and KOH. We further develop a new numerical model to compute the spatial distribution of the formed solids and residual brine as freezing progresses. If non-ice solids settle to the bottom, their deposits tend to have stacked hourglass shapes, widening each time the crystallization temperature of a new solid is reached. We discuss the applicability of this model to vertical fractures and global freezing of a subsurface ocean. These results inform (i) how compositional heterogeneities may affect the thermophysical properties of ice shells, which in turn influence convective and cryovolcanic transport, (ii) the compatibility of brine pockets with physicochemical conditions suitable for microbial life, and (iii) possible measurements of compositional heterogeneities within ice shells by spacecraft such as NASA’s Europa Clipper and ESA’s JUICE missions. The methodology developed here is applicable to other ice-covered ocean worlds.

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“…Building a more granular picture of Europa's ocean, however, will require incorporating these more sophisticated internal structure models into our Bayesian framework. In particular, ongoing work includes adapting our framework for models with radial conductivity structure (Eckhardt 1963;Srivastava 1966) to both probe the ocean's thermal structure, composition, and dynamics (Vance et al 2021) and enable disentangling ionospheric induction from the oceanic signal (e.g., Cochrane et al 2022). Adopting multilayer models will also enable the application of this framework to ocean worlds like Ganymede, which have been suggested to host multiple ocean layers (e.g., Vance et al 2014).…”

Section: Discussionmentioning

confidence: 99%

Revealing the Interior Structure of Icy Moons with a Bayesian Approach to Magnetic Induction Measurements

Biersteker¹,

Weiss²,

Cochrane

et al. 2023

Planet. Sci. J.

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Some icy moons and small bodies in the solar system are believed to host subsurface liquid water oceans. The interaction of these saline, electrically conductive oceans with time-varying external magnetic fields generates induced magnetic fields. Magnetometry observations of these induced fields in turn enable the detection and characterization of these oceans. We present a framework for characterizing the interiors of icy moons using multifrequency induction and Bayesian inference applied to magnetometry measurements anticipated from the upcoming Europa Clipper mission. Using simulated data from the Europa Clipper Magnetometer, our approach can accurately retrieve a wide range of plausible internal structures for Europa. In particular, the ocean conductivity is recovered to within ±50% for all internal structure scenarios considered, and the ocean thickness can be retrieved to within ±25 km for five out of seven scenarios. Characterization of the ice shell thickness to ±50% is possible for six of seven scenarios. Our recovery of the ice shell thickness is highly contingent on accurate modeling of magnetic fields arising from the interaction of Europa with the ambient magnetospheric plasma, while the ocean thickness is more modestly affected and the ocean conductivity retrieval is largely unchanged. Furthermore, we find that the addition of a priori constraints (e.g., static gravity measurements) can yield improved ocean characterization compared to magnetometry alone, suggesting that multi-instrument techniques can play a key role in revealing the interiors of Europa and other ocean worlds.

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Single‐ and Multi‐Pass Magnetometric Subsurface Ocean Detection and Characterization in Icy Worlds Using Principal Component Analysis (PCA): Application to Triton

Cited by 15 publications

References 49 publications

A Statistical Study of the Moon's Magnetotail Plasma Environment

A Statistical Study of the Moon's Magnetotail Plasma Environment

Salt Distribution from Freezing Intrusions in Ice Shells on Ocean Worlds: Application to Europa

Revealing the Interior Structure of Icy Moons with a Bayesian Approach to Magnetic Induction Measurements

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