HR: 14:25h
AN: G53C-04 INVITED     [Abstracts]
TI: Protoplanet Geodesy: Expectations for Understanding the Internal Structure of Vesta from the Dawn Mission
AU: * Zuber, M T
EM: zuber@mit.edu
AF: MIT, Dept. of Earth, Atmospheric and Planetary Sciences, Cambridge, MA 02139 United States
AU: Smith, D E
EM: David.E.Smith@nasa.gov
AF: NASA/GSFC, Code 690, Greenbelt, MD 20771 United States
AB: NASA's Dawn mission presents the opportunity to study the surface and interior of two of the four largest asteroids, Vesta and Ceres. Dawn will first orbit Vesta, which likely experienced melting in response to heating by short-lived heat-producing elements, and represents the only remaining large sample of a differentiated planetary embryo. To support mission design activities we have performed a simulation to address the recovery of Vesta's internal structure from observations that will be obtained in Dawn's primary mapping mission. We assume a four-layer base model of the interior of Vesta, consistent with the asteroid's observed mass and shape, as well as spectral observations of the surface and analogous meteorite composition and petrology. The model includes a kamacite (iron-nickel) core, olivine mantle, diogenite lower crust and eucrite upper crust. The model also includes a coarse representation of the large crater detected from Hubble Space telescope observations [Thomas et al., 1997]. We numerically integrate the asteroid density distribution to obtain the expected gravitational potential, and then simulate recovery of the gravity field for the planned Dawn tracking and orbital scenario. Our simulation shows that in Dawn's low-altitude mapping orbit the spacecraft will be sensitive to gravity perturbations to degree ~10 (half-wavelength resolution 80 km). In the optimistic case in which the asteroid's surface topography is uncompensated, the gravity field is expected to have low but detectable power. Vesta's crater has made the asteroid more oblate but the shape is currently less flattened than the equilibrium figure implied by the asteroid's current rotational period. Recovery of the C2,0 (flattening) term of the gravity field to 5%, certainly achievable by Dawn, will yield useful insight into the compensation state of the crater.
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 1221 Lunar and planetary geodesy and gravity (5417, 5450, 5714, 5744, 6019, 6250)
SC: Geodesy [G]
MN: Fall Meeting 2005