Updated Europa gravity field and interior structure from a reanalysis of Galileo tracking data

Casajus, Luis Gomez; Zannoni, Marco; Modenini, Dario; Tortora, Paolo; Nimmo, F.; Hoolst, Tim Van; Buccino, Dustin; Oudrhiri, Kamal

doi:10.1016/j.icarus.2020.114187

Cited by 33 publications

(52 citation statements)

References 39 publications

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“…The data analysis was carried out using a multi-arc approach, in which radiometric data obtained during the different encounters are analyzed together to produce a single solution of a set of "global" parameters, which do not vary among the arcs. The multi-arc approach has been successfully applied to the analysis of radio science data of several deep space missions (Iess et al, 2012c;Iess et al, 2014;Modenini & Tortora, 2014;Tortora et al, 2016;Zannoni et al, 2018;Durante et al, 2019;Gomez Casajus et al, 2019, Serra et al, 2019. The parameters were estimated using a weighted least-squares batch filter, which determines corrections to an a-priori dynamical model to minimize the difference between the real and the simulated measurements.…”

Section: Estimationmentioning

confidence: 99%

The gravity field and interior structure of Dione

Zannoni,

Hemingway,

Gomez Casajus

et al. 2020

Icarus

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During its mission in the Saturn system, Cassini performed five close flybys of Dione. During three of them, radio tracking data were collected during the closest approach, allowing estimation of the full degree-2 gravity field by precise spacecraft orbit determination.The gravity field of Dione is dominated by J2 and C22, for which our best estimates are J2 x 10 6 = 1496 ± 11 and C22 x 10 6 = 364.8 ± 1.8 (unnormalized coefficients, 1-σ uncertainty). Their ratio is J2/C22 = 4.102 ± 0.044, showing a significative departure (about 17-σ) from the theoretical value of 10/3, predicted for a relaxed body in slow, synchronous rotation around a planet. Therefore, it is not possible to retrieve the moment of inertia directly from the measured gravitational field.The interior structure of Dione is investigated by a combined analysis of its gravity and topography, which exhibits an even larger deviation from hydrostatic equilibrium, suggesting some degree of compensation. The gravity of Dione is far from the expectation for an undifferentiated hydrostatic body, so we built a series of three-layer models, and considered both Airy and Pratt compensation mechanisms. The interpretation is non-unique, but Dione's excess topography may suggest some degree of Airy-type isostasy, meaning that the outer ice shell is underlain by a higher density, lower viscosity layer, such as a subsurface liquid water ocean. The data permit a broad range of possibilities, but the best fitting models tend towards large shell thicknesses and small ocean thicknesses.

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Section: Estimationmentioning

confidence: 99%

The gravity field and interior structure of Dione

Zannoni,

Hemingway,

Gomez Casajus

et al. 2020

Icarus

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“…Gravity measurements performed by the Galileo spacecraft indicate that Europa's deep interior is likely differentiated into an iron core and a silicate mantle and is overlaid by a hydrosphere estimated to be between 80‐ and 170‐km thick (Anderson et al., 1998; Gomez Casajus et al., 2020). The thickness of the ice may be from a few kilometers to several tens of kilometer thick, depending on the efficiency of heat transfer through the ice shell and the total energy released by the silicate interior (Hussmann & Spohn, 2004; Tobie et al., 2003; Travis et al., 2012; Turtle & Pierazzo, 2001).…”

Section: Introductionmentioning

confidence: 99%

Tidally Induced Magmatic Pulses on the Oceanic Floor of Jupiter's Moon Europa

Běhounková

Tobie

Choblet

et al. 2021

Geophysical Research Letters

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The habitability of Europa's subsurface ocean is conditioned by heat released from the deep interior and by intensity of magmatic activity. Here, we investigate the melting of the silicate mantle through time and its consequences for seafloor magmatism by modeling Europa's internal heat production and transfer using a three‐dimensional numerical model. We show that melt can be produced during most of Europa's history due to the limited efficiency of internal cooling by thermal convection and the presence of radiogenic heating. The melting rate is amplified by tidal friction, possibly leading to magmatic pulses during enhanced eccentricity periods and focusing melting to high latitudes. The volume of generated melts during magmatic episodes is comparable to those involved in Large Igneous Provinces, commonly observed on Earth, and may impact ocean chemistry. We predict that gravity measurements, detection of anomalous H2/CH4, and astrometric data by future missions could confirm ongoing large‐scale seafloor activity.

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“…As a first step, a visual inspection of the Doppler residuals at 60 s count time was performed to highlight the presence of major signatures within the data and to identify possible causes for these features. The specific value of 60 s for the count time was selected since it represents a standard case for radio science applications (Casajus et al, 2021;Durante et al, 2019;Tortora et al, 2016;Zannoni et al, 2020). In fact, this value is sufficiently smaller than the characteristic time scales of the typical investigated processes and sufficiently large to avoid numerical noise issues (Zannoni & Tortora, 2013).…”

Section: Resultsmentioning

confidence: 99%

Performance Characterization of ESA's Tropospheric Delay Calibration System for Advanced Radio Science Experiments

et al. 2021

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Precise radiometric tracking is of key importance during operations of interplanetary missions and for advanced radio science applications. Radio science research performed on deep space missions like Cassini, Juno, BepiColombo, and the upcoming JUICE mission, rely on a combination of X and K a band radio links to mitigate the dispersive effects of propagation through interplanetary plasma, solar corona, and Earth ionosphere, leaving tropospheric delay as one of the main error contributors to Doppler and ranging measurements.To meet the demanding requirements of BepiColombo's Mercury Orbiter Radio science Experiment (MORE) (Iess et al., 2021) and JUICE's Geodesy and Geophysics of Jupiter and the Galilean Moons (3 GM) radio science experiment (Cappuccio et al., 2020), in terms of radiometric tracking accuracy and end-toend stability of the Doppler signals, ground-based microwave radiometers (MWR) are deemed as the most appropriate instruments for tropospheric delay calibration (Iess et al., 2009).Microwave radiometers have been extensively used in the past decades for the correction of tropospheric induced delay in astrometric and geodetic observations using very large base interferometry (VLBI) (Nikolic et al., 2013;Roy et al., 2007). However, their application to deep space radiometric tracking was originally introduced by the Jet Propulsion Laboratory (JPL) to support the Cassini radio science experiments, with the development and installation of two dedicated high-stability water vapor radiometers at the Goldstone deep space communication complex in California (

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Updated Europa gravity field and interior structure from a reanalysis of Galileo tracking data

Cited by 33 publications

References 39 publications

The gravity field and interior structure of Dione

The gravity field and interior structure of Dione

Tidally Induced Magmatic Pulses on the Oceanic Floor of Jupiter's Moon Europa

Performance Characterization of ESA's Tropospheric Delay Calibration System for Advanced Radio Science Experiments

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