Two spacecraft carrying identical pendulum gravity meters have landed on Mars, one at the equator and one at the North pole. Over a fixed period of time the pendulum at the equator is observed to oscillate 250 times compared with 251 times at the pole. Calculate the difference in the strength of gravity between the equator and the pole. Assuming Mars to be a spherically symmetric, rotating body, derive an expression for the difference in the strength of gravity at the Martian pole and equator due to the rotation of the planet and calculate its value. State what conclusions you draw when comparing the measured difference in gravity between the Martian equator and pole with the difference due to rotation.