Moon’s ice indicates past polar shift

Science : At the Lunar and Planetary Science Conference this week, an unexpected finding about the location of the Moon’s ice was announced. Unlike the ice found on most planetary bodies in the solar system, the Moon’s ice does not cover its north and south poles, but rather is located several degrees away from its poles. Matthew Siegler of the Planetary Science Institute in Dallas, Texas, and his colleagues reexamined data collected by the Lunar Prospector mission, which orbited the Moon 16 years ago. They realized that the two patches of lunar ice were directly opposite each other. The most likely explanation for this arrangement is that the ice was originally deposited at the lunar poles, and at some point, the Moon’s axis must have shifted by more than 5°. None of the known asteroid impacts are large enough or in the right location to have been the cause. Siegler’s team believes the outpouring of lava that created the Oceanus Procellarum some 3.5 billion years ago could have unbalanced the axis.