Range and Doppler tracking data from Mariners 6 and 7 have been used to obtain values for the ratio of the mass of the earth to that of the moon which are in substantial agreement with those determined from other Mariner and Pioneer spacecraft. There is an inconsistency of about 0.004 percent in values for the mass of the moon determined from lunar trajectories. A gravitational constant for Mars of 42,828.48 � 1.38 cubic kilometers per second per second, obtained on the basis of data collected during the 5 days prior to the closest approach of Mariner 6 to Mars, is in excellent agreement with the result obtained by Null from tracking data of Mariner 4