Paper No. 7
Presentation Time: 9:45 AM
VESTA'S TEMPERATURE: FIRST RESULTS FROM DAWN'S SURVEY ORBIT
TOSI, Federico1, CAPRIA, Maria Teresa
2, CORADINI, Angioletta
1, GRASSI, Davide
1, DE SANCTIS, Maria Cristina
2, CAPACCIONI, Fabrizio
2, FILACCHIONE, Gianrico
3, COMBE, Jean-Philippe
4, TITUS, Timothy
5 and RUSSELL, C.T.
6, (1)INAF, Istituto Nazionale di Astrofisica, IFSI, Istituto di Fisica dello Spazio Interplanetario, Via del Fosso del Cavaliere, 100, Rome, 000133, Italy, (2)INAF, Istituto Nazionale di Astrofisica, IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via del Fosso del Cavaliere, 100, Rome, 00133, Italy, (3)INAF, Istituto Nazionale di Astrofisica, IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via del Fosso del Cavaliere, 100, Rome, Italy, (4)Bear Fight Institute, P.O. Box 667, 22 Fiddler's Rd, Winthrop, WA 98862, (5)U.S. Geological Survey, Astrogeology Science Center, Flagstaff, AZ 86001, (6)Institute of Geophysics, University of California, Los Angeles, Los Angeles, CA 90095, federico.tosi@ifsi-roma.inaf.it
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.
