Topography of lobate scarps on Mercury: New constraints on the planet's contraction

Lobate scarps are landforms on Mercury that appear to have formed by thrust faulting and are thought to reflect global contraction due to cooling of the planet's interior. Topographic data for 10 mercurian lobate scarps, derived from Mariner 10 images using photoclinometry and digital stereoanalysis, indicate a range in maximum relief of 0.1 to 1.5 km and a range in horizontal shortening of 0.3 to 3.2 km, assuming fault-plane dips (θ) of 25°. Previous estimates of cumulative compressional strain recorded in the lobate scarps suggest a decrease in Mercury's radius of 1 to 2 km. Our estimate of compressional strain based on these new topographic measurements is ~0.056% (θ = 25°). This suggests that Mercury's radius decreased by <1 km.