Geological Society of America

T239 Dawn at Vesta: Initial Results from the Survey Orbit

Wednesday, 12 October 2011
8:00 AM - 12:00 PM
Room L100H-J

VESTA'S TEMPERATURE: FIRST RESULTS FROM DAWN'S SURVEY ORBIT

Paper number: T239-7
Program: Technical Sessions
Time: 9:45 AM – 10:00 AM

Authors

Federico Tosi Presenting Author
IFSI, Istituto di Fisica dello Spazio Interplanetario, Rome, N/A
C.T. Russell
University of California, Los Angeles, Los Angeles, CA
Maria Teresa Capria
IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Rome, N/A
Angioletta Coradini
IFSI, Istituto di Fisica dello Spazio Interplanetario, Rome, N/A
Davide Grassi
IFSI, Istituto di Fisica dello Spazio Interplanetario, Rome, N/A
Maria Cristina De Sanctis
IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Rome, N/A
Fabrizio Capaccioni
IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Rome, N/A
Gianrico Filacchione
IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Rome, N/A
Jean-Philippe Combe
Bear Fight Institute, Winthrop, WA
Timothy Titus
USGSAstrogeology, Flagstaff, AZ

Abstract

The Dawn spacecraft is orbiting around Vesta, the second-most-massive object in the main asteroid belt and the largest differentiated planetesimal that survived to the primordial bombardment. The onboard instruments are mapping its surface at various resolutions and in different regions of the electromagnetic spectrum. The VIR imaging spectrometer is acquiring data in the overall spectral range 0.4-5.1 microns. VIR infrared spectra in the range longward of 3 microns are affected by the thermal emission of the asteroid, hence the measured radiance in that spectral region can be used to retrieve surface temperatures and spectral emissivities by means of temperature-retrieval algorithms, with the goal of obtaining spatially- resolved temperature maps of the surface.

Variations of temperatures across the surface with respect to local solar times provide key information on the thermal properties (such as thermal thermal inertia) of materials composing the surface. Any hint we will be able to obtain on these properties will help us, together with the knowledge of composition, in the determination of the nature and physical status of the different areas of Vesta’s surface.

Due to instrumental constraints, the VIR spectrometer is sensitive only to temperatures greater than 170-180 K (hence only dayside temperatures of Vesta can be retrieved). In order to complement the information derived from the infrared spectra, theoretical codes solving the heat equation are needed. These codes will help us in the determination of the thermal inertia needed to explain the measured temperatures.

The results of both the temperature retrieval algorithms and the thermal codes will be checked against all the available determination of Vesta’s temperatures as obtained from on-ground and satellite observation.