A team of researchers from the Jet Propulsion Laboratory, California Institute of Technology and the Royal Observatory of Belgium have found evidence of the Chandler wobble on Mars. In an article published in the journal Geophysical Research Letters, scientists describe their study of data obtained over decades using Mars probes and their findings.
About a hundred years ago, American astronomer Seth Carlo Chandler discovered that imperfectly shaped objects (such as planets and their poles) sometimes deviate from the axis of rotation. This phenomenon became known as the Chandler wobble. Previously, they were seen only on Earth, where the displacement of the rotation poles occurs with a period of 433 days, and their amplitude reaches 15 meters. There is still no exact answer to why this is happening. Scientists suggest that the fluctuations are influenced by processes in the ocean and in the Earth’s atmosphere.
Later, researchers suggested that there is probably a Chandler wobble on other planets. However, it was not previously observed. The fact is that measuring the wobble at the scale of the planet requires accurate measurements over many years.
Finally, such data became available to scientists thanks to the work of space probes that have orbited Mars for many years: Mars Reconnaissance Orbiter, Mars Global Surveyor and Mars Odyssey. The data has been collected for 18 years and included measurements of gravitational effects on the spacecraft. It turned out that Mars does have a Chandler wobble. Although, it is worth noting, it is less pronounced than the terrestrial one: the planet deviates from its axis by only 10 cm over a 200-day period.