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Science 12 July 1974:
Vol. 185. no. 4146, pp. 179 - 180
DOI: 10.1126/science.185.4146.179
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Articles

Mercury: Results on Mass, Radius, Ionosphere, and Atmosphere from Mariner 10 Dual-Frequency Radio Signals

H. T. Howard 1, G. L. Tyler 1, P. B. Esposito 2, J. D. Anderson 2, R. D. Reasenberg 3, I. I. Shapiro 3, G. Fjeldbo 4, A. J. Kliore 4, G. S. Levy 4, D. L. Brunn 4, R. Dickinson 4, R. E. Edelson 4, W. L. Martin 4, R. B. Postal 4, B. Seidel 4, T. T. Sesplaukis 4, D. L. Shirley 4, C. T. Stelzried 4, D. N. Sweetnam 4, G. E. Wood 4, and A. I. Zygielbaum 4

1 Center for Radar Astronomy, Stanford University, Stanford, California 94305
2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91103
3 Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge 02139
4 Jet Propulsion Laboratory

Analysis of the radio-tracking data from Mariner 10 yields 6,023,600 ± 600 for the ratio of the mass of the sun to that of Mercury, in very good agreement with values determined earlier from radar data alone. Occultation measurements yielded values for the radius of Mercury of 2440 ± 2 and 2438 ± 2 kilometers at laditudes of 2°N and 68°N, respectively, again in close agreement with the average equatorial radius of 2439 ± 1 kilometers determined from radar data. The mean density of 5.44 grams per cubic centimeter deduced for Mercury from Mariner 10 data thus virtually coincides with the prior determination. No evidence of either an ionosphere or an atmosphere was found, with the data yielding upper bounds on the electron density of about 1500 and 4000 electrons per cubic centimeter on the dayside and nightside, respectively, and an inferred upper bound on the surface pressure of 10-8 millibar.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Observations at Mercury Encounter by the Plasma Science Experiment on Mariner 10.
K. W. Ogilvie, J. D. Scudder, R. E. Hartle, G. L. Siscoe, H. S. Bridge, A. J. Lazarus, J. R. Asbridge, S. J. Bame, and C. M. Yeates (1974)
Science 185, 145-151
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