Measuring tidal deformations by laser altimetry. A performance model for the Ganymede Laser Altimeter

Steinbrügge, Gregor; Stark, Alexander; Hußmann, H.; Sohl, F.; Oberst, J.

doi:10.1016/j.pss.2015.06.013

Cited by 38 publications

(36 citation statements)

References 24 publications

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“…Wahr et al [] consider tidal deformation on Europa and show that 1+| k 2 |−| h 2 | linearly depends on shell thickness and thus could be a good index for shell thickness. Steinbrügge et al [] show that this is also the case for Ganymede. These works, however, use fully elastic models with a given ice rigidity.…”

Section: Resultsmentioning

confidence: 69%

“…We found that a decrease in the error for | h 2 | leads to a decrease in the uncertainty in D sh if | k 2 | is constrained (Figure b). The nominal error in the | h 2 | measurements using Ganymede Laser Altimeter (GALA) on board the JUICE spacecraft is ∼2% and decreases with increasing number of crossover points [ Steinbrügge et al , ]. Thus, our results highlight the importance of an extended mission for altimetric measurements as well as of collaborative analyses of topography and gravity field data for constraining the interior structure of Ganymede.…”

Section: Resultsmentioning

confidence: 99%

“…Figure shows our interior structure model obtained through the procedures described above. The maximum shell thickness is found to be ∼155 km, which is much thinner than that modeled by Steinbrügge et al []. This is simply because the work by Steinbrügge et al [] does not consider the phase diagram of H 2 O in detail.…”

Section: Modelmentioning

confidence: 99%

“…In 2030s, Jupiter Icy Moons Explorer (JUICE) will orbit Ganymede carrying multiple scientific instruments to reveal the environment, surface, and interior of Ganymede [e.g., Grasset et al , ]. During the mission lifetime, Ganymede Laser Altimeter (GALA) on board the JUICE spacecraft will make multiple measurements at many geographically fixed locations to provide a time series of surface displacement [ Steinbrügge et al , ]. Considering Ganymede's nonzero eccentricity, the temporal changes of the surface displacement are likely to be due to tidal deformation.…”

Section: Introductionmentioning

confidence: 99%

“…Although the tidal response of Ganymede has already been investigated by several authors, previous models generally made simplifying assumptions. For example, the models used by Moore and Schubert [] ignore the strong temperature dependence of ice viscosity, and those by Steinbrügge et al [] assume a fully elastic model. Another study using 3‐D modeling by A et al [] adopts a depth‐dependent viscosity profile, though the parameter ranges investigated are limited.…”

Section: Introductionmentioning

confidence: 99%

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Tidal deformation of Ganymede: Sensitivity of Love numbers on the interior structure

et al. 2016

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Tidal deformation of icy satellites provides crucial information on their subsurface structures. In this study, we investigate the parameter dependence of the tidal displacement and potential Love numbers (i.e., h2 and k2, respectively) of Ganymede. Our results indicate that Love numbers for Ganymede models without a subsurface ocean are not necessarily smaller than those with a subsurface ocean. The phase lag, however, depends primarily on the presence/absence of a subsurface ocean. Thus, the determination of the phase lag would be of importance to infer whether Ganymede possesses a subsurface ocean or not based only on geodetic measurements. Our results also indicate that the major control on Love numbers is the thickness of the ice shell if Ganymede possesses a subsurface ocean. This result, however, does not necessarily indicate that measurement of either of h2 or k2 alone is sufficient to estimate the shell thickness; while a thin shell leads to large h2 and k2 independent of parameters, a thick shell does not necessarily lead to small h2 and k2. We found that to reduce the uncertainty in the shell thickness, constraining k2 in addition to h2 is necessary, highlighting the importance of collaborative analyses of topography and gravity field data.

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Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tidal deformation of Ganymede: Sensitivity of Love numbers on the interior structure

et al. 2016

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Geophysical Investigations of Habitability in Ice‐Covered Ocean Worlds

et al. 2018

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Geophysical measurements can reveal the structures and thermal states of icy ocean worlds. The interior density, temperature, sound speed, and electrical conductivity thus characterize their habitability. We explore the variability and correlation of these parameters using 1‐D internal structure models. We invoke thermodynamic consistency using available thermodynamics of aqueous MgSO4, NaCl (as seawater), and NH3; pure water ice phases I, II, III, V, and VI; silicates; and any metallic core that may be present. Model results suggest, for Europa, that combinations of geophysical parameters might be used to distinguish an oxidized ocean dominated by MgSO4 from a more reduced ocean dominated by NaCl. In contrast with Jupiter's icy ocean moons, Titan and Enceladus have low‐density rocky interiors, with minimal or no metallic core. The low‐density rocky core of Enceladus may comprise hydrated minerals or anhydrous minerals with high porosity. Cassini gravity data for Titan indicate a high tidal potential Love number (k2>0.6), which requires a dense internal ocean (ρocean>1,200 kg m−3) and icy lithosphere thinner than 100 km. In that case, Titan may have little or no high‐pressure ice, or a surprisingly deep water‐rock interface more than 500 km below the surface, covered only by ice VI. Ganymede's water‐rock interface is the deepest among known ocean worlds, at around 800 km. Its ocean may contain multiple phases of high‐pressure ice, which will become buoyant if the ocean is sufficiently salty. Callisto's interior structure may be intermediate to those of Titan and Europa, with a water‐rock interface 250 km below the surface covered by ice V but not ice VI.

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Determination of the lunar body tide from global laser altimetry data

Thor

Kallenbach

Christensen

et al. 2020

J Geod

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We use global data from the Lunar Orbiter Laser Altimeter (LOLA) to retrieve the lunar tidal Love number $$h_2$$ h 2 and find $$h_2 = 0.0387\pm 0.0025$$ h 2 = 0.0387 ± 0.0025 . This result is in agreement with previous estimates from laser altimetry using crossover points of LOLA profiles. The Love numbers $$k_2$$ k 2 and $$h_2$$ h 2 are key constraints on planetary interior models. We further develop and apply a retrieval method based on a simultaneous inversion for the topography and the tidal signal benefiting from the large volume of LOLA data. By the application to the lunar tides, we also demonstrate the potential of the method for future altimetry experiments at other planetary bodies. The results of this study are very promising with respect to the determination of Mercury’s and Ganymede’s $$h_2$$ h 2 from future altimeter measurements.

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Measuring tidal deformations by laser altimetry. A performance model for the Ganymede Laser Altimeter

Cited by 38 publications

References 24 publications

Tidal deformation of Ganymede: Sensitivity of Love numbers on the interior structure

Tidal deformation of Ganymede: Sensitivity of Love numbers on the interior structure

Geophysical Investigations of Habitability in Ice‐Covered Ocean Worlds

Determination of the lunar body tide from global laser altimetry data

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