Lobate scarps are landforms on Mercury that appear to have formed by t
hrust faulting and are thought to reflect global contraction due to co
oling of the planet's interior. Topographic data for 10 mercurian loba
te scarps, derived from Mariner 10 images using photoclinometry and di
gital 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 fa
ult-plane dips (theta) of 25 degrees. 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 strai
n based on these new topographic measurements is similar to 0.056% (th
eta = 25 degrees). This suggests that Mercury's radius decreased by <1
km.