Mercury's radius change estimates revisited using MESSENGER data

Mapping tectonic features using MESSENGER data mainly acquired at high Sun incidence angle (>50°) reveals previously undetected structures. The analysis of the latter features determines an upward revision of measurements of density and spatial distribution of tectonism and thus of estimates of average contractional strain and planetary radius decrease. We calculated an average surface contraction of ∼0.23-0.30% (∼0.28% for fault dip angle θ = 30°) within an area corresponding to 21% of the planet. This strain, extrapolated to the entire surface, corresponds to a decrease in radius of about 2.4-3.6 km (∼3.0 km for θ = 30°). These values are three-four times higher with respect to previous estimates and are compatible with results from thermomechanical models.