Polar hydrogen deposits indicate Moon’s spin axis has shifted
DOI: 10.1063/PT.5.029684
Guardian : The orientation of the Moon has changed from what it was several billion years ago, according to James Keane of the University of Arizona and his colleagues. The researchers base their finding on a reexamination of data collected in the late 1990s by NASA’s Lunar Prospector. They found that hydrogen deposits in both the north and south polar regions are displaced from the Moon’s current axis by about 5.5 degrees, which indicates that true polar wander has occurred. The researchers attribute the Moon’s shift to volcanic activity more than 3.5 billion years ago. The extreme heat could have affected the Moon’s density structure in the deep mantle and caused perturbations that altered its spin. Further, the scientists propose that residual heat from that thermal anomaly continues to affect the Moon’s orientation.