In a study titled, "Detection of the Chandler Wobble of Mars From Orbiting Spacecraft" published in Geophysical Research Letters, readings from the Mars Odyssey, Mars Reconnaissance Orbiter, and Mars Global Surveyor confirm the axis of Mars is wobbling.
Scientists observed the Chandler wobble on Mars, a repeated displacement of the poles on the planet's surface away from the average axis of rotation, in a first for a solar system entity other than Earth.
A minor deviation in the Planet's axis of rotation compared to the solid earth, which was observed by American astronomer Seth Carlo Chandler in 1891, is the Chandler wobble or latitude variance. The axis of the Planet shifts 9 meters (30 feet) every 433 days.
The Chandler wobble is a type of motion that can be observed in spinning non-spherical objects.
“[The Chandler wobble] is a very small signal, typically,” said Alex Konopliv, an aerospace engineer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “You need many years and high-quality data to detect it,”
When a spinning entity is not a smooth sphere, the Chandler wobble appears. This desequilibrium influences the spin. The effect is a wiggle like the winging top as it loses momentum instead of the steady movement of a perfectly balanced globe.
Measures by spaceships circling Mars for almost 2 decades showed that the planet's poles, with a period of about 207 days replicated, are up to 10 centimeters from the average axis of rotation.