Spin state and moment of inertia of Venus
Abstract
Fundamental properties of the planet Venus, such as its internal mass distribution and variations in length of day, have remained unknown. We used Earthbased observations of radar speckles tied to the rotation of Venus obtained in 20062020 to measure its spin axis orientation, spin precession rate, moment of inertia and lengthofday variations. Venus is tilted by 2.6392 ± 0.0008 deg (1σ) with respect to its orbital plane. The spin axis precesses at a rate of 44.58 ± 3.3 arcsec per year (1σ), 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 in the 20062020 interval is 243.0226 ± 0.0013 Earth days (1σ). The spin period of the solid planet exhibits variations of 61 ppm (~20 min) with a possible diurnal or semidiurnal forcing. The lengthofday variations imply that changes in atmospheric angular momentum of at least ~4% are transferred to the solid planet.
 Publication:

Nature Astronomy
 Pub Date:
 2021
 DOI:
 10.1038/s41550021013397
 arXiv:
 arXiv:2103.01504
 Bibcode:
 2021NatAs...5..676M
 Keywords:

 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 20 pages, 7 figures, supplementary information. Submitted to Nature Astronomy on October 14, 2020