Researchers find Mars has a Chandler wobble

[beecee]

https://phys.org/news/2021-01-mars-chandler.html

A combined team of researchers from the Jet Propulsion Laboratory, California Institute of Technology and the Royal Observatory of Belgium, has found evidence that Mars has a Chandler wobble. In their paper published in the journal Geophysical Research Letters, the group describes their study of decades of data from Mars probes and what it showed them.

Approximately a century ago, astronomer Seth Carlo Chandler discovered that imperfectly round objects (such as planets) sometimes spin off their axis for periods of time. The phenomenon has come to be known as the Chandler wobble, and has been documented for planet Earth, which veers from its axis for distances up to 30 feet in a pattern that repeats approximately every 433 days. Researchers have suggested that other planets likely have a Chandler wobble, but until now, it has never been observed because measuring it on the planet scale requires precise measurements over many years. In this new effort, the researchers obtained the right kind of data from space probes that orbited Mars over many years: The Mars Reconnaissance Orbiter, the Mars Global Surveyor and Mars Odyssey. The data from the craft spanned 18 years and was considered to be precise enough to measure any existing Chandler wobble.

more at link............................

 

the paper: 

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL090568

Detection of the Chandler Wobble of Mars From Orbiting Spacecraft:

Abstract

For the first time for any planetary body other than the Earth, the free wobble of the pole called the Chandler wobble has been detected for Mars with a period of 206.9 ± 0.5 days and amplitude of 10 cm from radio tracking observations of Mars Odyssey, Mars Reconnaissance Orbiter (MRO), and Mars Global Surveyor (MGS), in order of decreasing sensitivity. The motion of the rotation pole location on the surface of Mars, or polar motion, is observed using two different approaches: (1) joint global estimates of Mars' orientation and its gravity field and (2) time series solutions of C₂₁ and S₂₁. For Mars interior models, the Chandler wobble period is combined with other measurements including the moments of inertia from our estimated precession rate  and tidal Love number k₂ = 0.169 ± 0.006. The Chandler wobble period constrains the rheology of the Martian mantle and in particular its long‐term frequency dependence.

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I actually thought the Chandler wobble was produced by the gravitational tug of the Moon. It seems that's not exactly right.....https://en.wikipedia.org/wiki/Chandler_wobble The full explanation for the period also involves the fluid nature of the Earth's core and oceans—the wobble, in fact, produces a very small ocean tide with an amplitude of approximately 6 mm (¹⁄₄ in), called a "pole tide", which is the only tide not caused by an extraterrestrial body. Because the Earth is not a rigid body, the Chandler wobble should die down with a time constant of about 68 years.

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Also it seems that the Chandler wobble was predicted by Newton in his Principia Mathmatica....https://en.wikipedia.org/wiki/Chandler_wobble  The existence of Earth's free nutation was predicted by Isaac Newton in Corollaries 20 to 22 of Proposition 66, Book 1 of the Philosophiæ Naturalis Principia Mathematica, and by Leonhard Euler in 1765 as part of his studies of the dynamics of rotating bodies. 

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More evidence of the predictive power of science, even going back near 300 years!!!  

Edited January 11, 2021 by beecee