Abstract
Due to its eccentric orbit, Mercury experiences varying gravitational
pull from the Sun along its orbit, leading to periodic surface tidal
deformation. The previous measurement of Mercury’s tidal h2 by Bertone
et al. (2021) is based on minimizing height differences at cross-overs
of the Mercury Laser Altimeter (MLA) profiles. However, this method can
suffer from significant interpolation errors. In this study, we apply an
alternative approach, which is based on the co-registration of
reprocessed MLA profiles. For the reprocessing, we account for the
pointing aberration and incorporate an updated spacecraft orbit model.
Within the study region of 77°N to 84°N, we obtain a tidal h2 of
0.92±0.51 (3-σ). This value is compatible with current interior
structure and rheology models, but significantly smaller than the
previous estimate of 1.55±0.65 (3-σ). When combined with recent tidal k2
estimates, our measurement favors a small to medium-sized inner core.