Science. 1972 Jan 21;175(4019):317-20. doi: 10.1126/science.175.4019.317.
Analysis of the Mariner 9 radio-tracking data shows that the Martian gravity field is rougher than that of Earth or the moon, and that the accepted direction of Mars's rotation axis is in error by about 0.5 degrees . The new value for the pole direction for the epoch 1971.9, referred to the mean equatorial system of 1950.0, is right ascension alpha= 317.3 degrees +/- 0.3 degrees , declination delta = 52.6 degrees +/- 0.2 degrees . The values found for the coefficients of the low-order harmonics of Mars's gravity field are as follows: J(2)=(1.96+/-0.01)x10(-3), referred to an equatorial radius of 3394 kilometers; C(22) = -(5 +/- 1) x 10(-5); and S(22) = (3 +/- 1) x 10(-5). The value for J(2) is in excellent agreement with the result from, Wilkins' analysis of the observations of Phobos. The other two coefficients imply a value of (2.5 +/- 0.5) x 10(-4) for the fractional difference in the principal equatorial moments of inertia; the axis of the minimum moment passes near 105 degrees W.
分析水手 9 号的无线电跟踪数据表明，火星的重力场比地球或月球的更不规则，而且人们公认的火星自转轴方向存在约 0.5 度的误差。1971.9 时极的新值，相对于 1950.0 的平均赤道系统，赤经α=317.3 度 +/- 0.3 度，赤纬δ=52.6 度 +/- 0.2 度。发现火星重力场低阶谐系数的值如下：J(2)=(1.96+/-0.01)x10(-3)，相对于赤道半径 3394 公里；C(22)=-(5+/-1) x 10(-5)；和 S(22)=(3+/-1) x 10(-5)。J(2)的值与 Wilkins 分析 Phobos 观测结果的结果非常吻合。后两个系数意味着主赤道转动惯量的分数差的值为 (2.5+/-0.5) x 10(-4)；最小转动惯量轴位于西经 105 度附近。
