The Spin State And Moment Of Inertia Of Venus

©NASA

Venus

Fundamental properties of the planet Venus, such as its internal mass distribution and variations in length of day, have remained unknown.

We used Earth-based observations of radar speckles tied to the rotation of Venus obtained in 2006-2020 to measure its spin axis orientation, spin precession rate, moment of inertia, and length-of-day variations. Venus is tilted by 2.6392 ± 0.0008 degrees (1σ) with respect to its orbital plane.

The spin axis precesses at a rate of 44.58 ± 3.3 arcseconds per year, which gives a normalized moment of inertia of 0.337 ± 0.024 and yields a rough estimate of the size of the core. The average sidereal day on Venus is currently 243.0226 ± 0.0013 Earth days (1σ). The spin period of the solid planet exhibits variations of 61 ppm (∼20 minutes) with a possible diurnal or semidiurnal forcing. The length-of-day variations imply that changes in atmospheric angular momentum of at least ∼4% are transferred to the solid planet.

Jean-Luc Margot, Donald B. Campbell, Jon D. Giorgini, Joseph S. Jao, Lawrence G. Snedeker, Frank D. Ghigo, Amber Bonsall

Comments: 20 pages, 7 figures, supplementary information. Submitted to Nature Astronomy on October 14, 2020
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2103.01504 [astro-ph.EP] (or arXiv:2103.01504v1 [astro-ph.EP] for this version)
Submission history
From: Jean-Luc Margot
[v1] Tue, 2 Mar 2021 06:45:24 UTC (4,995 KB)
https://arxiv.org/abs/2103.01504

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