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| Titel |
Interior Structure and Tidal Response of Mercury |
| VerfasserIn |
Teresa Steinke, Frank Sohl, Hauke Hussmann, Martin Knapmeyer, Frank Walter Wagner |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078191
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| Zusammenfassung |
| Recent determinations of Mercury’s mean density, polar moment of inertia factor, and the
inertia of its solid outer shell provide strong constraints on the radius of its liquid core. We
present an ensemble of spherically symmetric interior structure models that all satisfy the
observational constraints. The models consist of a pure iron solid inner core, a liquid Fe-FeS
outer core, a peridotite mantle and a crust predominantly composed of plagioclase. The
sulfur content in the outer core, the iron and magnesium content of the mantle, and
the crustal thickness vary throughout the ensemble. Comparison of observed and
predicted moments of inertia yields admissible ranges for the outer core radius and
the mantle density. From this model ensemble we derive geophysical observables
that would allow further constraining the interior structure of Mercury in future
experiments.
The moment of inertia constraints allow for both forsterite and fayalite rich mantle
compositions. Variations of mantle density trade off with crustal thickness and core
composition. This non-uniqueness could be resolved using seismic travel time observations:
since the P wave velocity of a fayalite mantle is significantly lower than that of the
plagioclase-rich crust, a shadow zone arises as a clear discriminant between the two
end-member compositions.
The planet’s response to solar tidal forcing strongly depends on its interior structure and
rheological properties and can be parameterized in terms of the surface body tide Love
numbers k2 and h2, respectively. We employ the frequency-dependent Maxwell
rheology to calculate the body tide Love numbers for the main tidal period (87.97
days) using the density, rigidity and viscosity profiles of our structural models.
We obtain values between 0.38 and 0.65 for k2 and between 0.70 and 1.12 for h2,
respectively, thereby indicating the substantial tidal response of Mercury’s interior.
Furthermore we find that, via viscosity and rigidity, both k2 and h2 are foremost
dependent on the mantle composition and less affected by the inner and outer core radii.
The peak-to-peak radial displacement amplitudes are predicted to range from 47
cm to 76 cm in polar regions and from 139 cm to 223 cm in equatorial regions,
sufficiently large to be detected by laser altimetry from the BepiColombo spacecraft. |
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