Experimental Test of the Variability ofGUsing Viking Lander Ranging Data

Results are presented from the analysis of solar system astrometric data, notably the range data to the Viking landers on Mars. A least-squares fit of the parameters of the solar system model to these data limits a simple time variation in the effective Newtonian gravitational constant to (0.2 ± 0.4) × ${10}^{-11\mathrm{}}$ ${\mathrm{yr}}^{-1\mathrm{}}$ and a rate of drift of atomic clocks relative to the implicit clock of relativistic dynamics to (0.1 ± 0.8) × ${10}^{-11\mathrm{}}$ ${\mathrm{yr}}^{-1\mathrm{}}$. The error limits quoted are the result of uncertainties in the masses of the asteroids.