One of the ways in which Mars changes is similar to one of the ways the Earth changes — Mars’ axis wobbles.

Known as the Chandler wobble, these tiny shifts or wiggles change where the axis of a planet points, when that planet isn’t a perfect sphere. We know Earth is an oblate spheroid, meaning that our planet bulges around the equator due to the Earth’s rotation. And the wobble is similar in effect to how a top sways as it loses speed during its spin. In the case of Earth, that wobble is about 3 to 6 meters; on Mars, only about 10 centimeters.

These new measurements are the results of almost two decades’ worth of data collection on gravitational effects by NASA’s Mars Odyssey and Mars Reconnaissance Orbiter. Per the article: The large quantity of data, collected over 18 years and not available during earlier analyses, ensured that the identified wobble was intrinsic to the planet’s shape and interior, rather than outside factors like seasonal melting of polar ice caps.

So why doesn’t the Earth’s wobble slow down with the wobble like a top? The motion should dampen, but instead, it persists due to the fluctuations in our ocean bottom and atmospheric pressure. We don’t yet understand why the wobble persists on Mars, but this newfound Chandler wobble may provide us insight into the interior of the red planet, particularly how the mantle deforms over longer periods of time since the motion is driven by the properties of that mantle. The full paper can be found in Geophysical Research Letters. 

More Information:

Eos article 

“Detection of the Chandler Wobble of Mars From Orbiting Spacecraft,” Alex S. Konopliv et al., 2020 October 13, Geophysical Research Letters