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Science 5 December 1997:
Vol. 278. no. 5344, pp. 1749 - 1752
DOI: 10.1126/science.278.5344.1749
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Reports

Interior Structure and Seasonal Mass Redistribution of Mars from Radio Tracking of Mars Pathfinder

W. M. Folkner, * C. F. Yoder, D. N. Yuan, E. M. Standish, R. A. Preston

Doppler and range measurements to the Mars Pathfinder lander made using its radio communications system have been combined with similar measurements from the Viking landers to estimate improved values of the precession of Mars' pole of rotation and the variation in Mars' rotation rate. The observed precession of -7576 ± 35 milliarc seconds of angle per year implies a dense core and constrains possible models of interior composition. The estimated annual variation in rotation is in good agreement with a model of seasonal mass exchange of carbon dioxide between the atmosphere and ice caps.

Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
*   To whom correspondence should be addressed. E-mail: william.folkner{at}jpl.nasa.gov

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Science. ISSN 0036-8075 (print), 1095-9203 (online)