Volcanic activity may have tilted Mars’s axis of rotation

New Scientist : Mars hosts the largest volcanic complex in the solar system. Called the Tharsis region, it comprises volcanic rock more than 10 km thick spread over an area about 5000 km across. As the region formed, it bent the planet’s crust and was thought to have influenced the formation and direction of river networks. Based on the circular pattern of those networks, however, Sylvain Bouley of Université Paris–Sud and his colleagues have proposed that the rivers formed before or concurrently with the formation of the Tharsis region. The researchers suspect that as Tharsis formed, it altered the orientation of the planet with respect to its spin axis, changing the geographic locations of the north and south poles. That rearrangement could have greatly affected Mars’s climate and contributed to the loss of flowing liquid water on the planet’s surface.