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| Titel |
Mercury’s interior from MESSENGER geodetic measurements |
| VerfasserIn |
Antonio Genova, Erwan Mazarico, Sander Goossens, Frank G. Lemoine, Gregory A. Neumann, David E. Smith, Maria T. Zuber, Sean C. Solomon |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128000
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| Publikation (Nr.) |
 EGU/EGU2016-7940.pdf |
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| Zusammenfassung |
| The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER)
spacecraft completed more than 4 years of operations in orbit about Mercury. One of the main
mission goals was the determination of the interior structure of Mercury enabled by geodetic
observations of the topography, gravity field, rotation, and tides by the Mercury Laser
Altimeter (MLA) and radio science system.
MLA acquired over 25 million individual measurements of Mercury’s shape that are
mostly limited to the northern hemisphere because of MESSENGER’s eccentric orbit.
However, the lack of laser altimetry in the southern hemisphere has been partly compensated
by ∼400 occultations of spacecraft radio signals.
X-band radio tracking data collected by the NASA Deep Space Network (DSN) allowed
the determination of Mercury’s gravity field to spherical harmonic degree and order 100, the
planet’s obliquity, and the Love number k2.
The combination of altimetry and radio measurements provides a powerful tool for the
investigation of Mercury’s orientation and tides, which enable a better understanding of the
interior structure of the planet.
The MLA measurements have been assembled into a digital elevation model
(DEM) of the northern hemisphere. We then used individual altimetric measurements
from the spacecraft for orbit determination, together with the radio tracking, over a
continuous span of time using a batch least-squares filter. All observations were
combined to recover directly the gravity field coefficients, obliquity, librations, and tides
by minimizing the discrepancies between the computed observables and actual
measurements.
We will present the estimated 100×100 gravity field model, the obliquity, the Love
number k2, and, for the first time, the tidal phase lag φ and the amplitude of the longitudinal
libration from radio and altimetry data. The k2 phase provides information on Mercury’s
dissipation and mantle viscosity and allows a determination of the Q factor. A refinement of
the longitudinal libration, on the other hand, helps to constrain the ratio of the polar
moment of inertia of Mercury’s crust and mantle (Cm) to that of the planet (C). |
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