Mercury's moment of inertia from spin and gravity data (original) (raw)
ADS
;
- Peale, Stanton J. ;
- Solomon, Sean C. ;
- Hauck, Steven A., II ;
- Ghigo, Frank D. ;
- Jurgens, Raymond F. ;
- Yseboodt, Marie ;
- Giorgini, Jon D. ;
- Padovan, Sebastiano ;
- Campbell, Donald B.
Abstract
Earth-based radar observations of the spin state of Mercury at 35 epochs between 2002 and 2012 reveal that its spin axis is tilted by (2.04 ± 0.08) arc min with respect to the orbit normal. The direction of the tilt suggests that Mercury is in or near a Cassini state. Observed rotation rate variations clearly exhibit an 88-day libration pattern which is due to solar gravitational torques acting on the asymmetrically shaped planet. The amplitude of the forced libration, (38.5 ± 1.6) arc sec, corresponds to a longitudinal displacement of ∼450 m at the equator. Combining these measurements of the spin properties with second-degree gravitational harmonics (Smith et al., 2012) provides an estimate of the polar moment of inertia of Mercury C/MR2 = 0.346 ± 0.014, where M and R are Mercury's mass and radius. The fraction of the moment that corresponds to the outer librating shell, which can be used to estimate the size of the core, is Cm/C = 0.431 ± 0.025.
Publication:
Journal of Geophysical Research (Planets)
Pub Date:
October 2012
DOI:
Bibcode:
Keywords:
- Planetary Sciences: Solid Surface Planets: Interiors (8147);
- Planetary Sciences: Solar System Objects: Mercury