Computer Model Adds Credence to Wet Mars Theory

Mars' axis of rotation may have moved dramatically in the past, according to a mathematical model by Taylor Perron and his team at the University of California at Berkeley. This explains why Martian "shorelines" appear to rise and fall and seems to strengthen the case for Mars having once been a wet planet.

Many scientists have argued that there are geological features on Mars which resemble the shorelines of ancient oceans. But in the 1990s, NASA's Mars Global Surveyor Spacecraft showed that their height varies by about 2.5km across the planet. This has led some scientists to doubt that the features could represent a shoreline, because an ocean should normally be nearly level.

 The UCB team have calculated that if Mars' rotation axis shifted dramatically billions of years ago, then the variations in Mars' shorelines make sense. The movement of the axis would cause the crust to deform, because a spinning planet will bulge around its equator.  The team reported in Nature that two polar shifts of up to 50 degrees form today's orientation could account for the current appearance of Mars' shoreline.

 The shift in the axis of the rotation could have been caused by flooding of a huge ocean or by thermal convection within Mars' hot interior.

 Mark Richards, a member of the team, stated, "This really confirms that there was an ocean on Mars. This is a beautiful result."