  Titan's polar surface is dotted with hundreds of lacustrine depressions.
Based on the hypothesis that they are karstic in origin, we aim at determining
the efficiency of surface dissolution as a landshaping process on Titan, in a
comparative planetology perspective with the Earth as reference. Our approach
is based on the calculation of solutional denudation rates and allow inference
of formation timescales for topographic depressions developed by chemical
erosion on both planetary bodies. The model depends on the solubility of solids
in liquids, the density of solids and liquids, and the average annual net
rainfall rates. We compute and compare the denudation rates of pure solid
organics in liquid hydrocarbons and of minerals in liquid water over Titan and
Earth timescales. We then investigate the denudation rates of a superficial
organic layer in liquid methane over one Titan year. At this timescale, such a
layer on Titan would behave like salts or carbonates on Earth depending on its
composition, which means that dissolution processes would likely occur but
would be 30 times slower on Titan compared to the Earth due to the seasonality
of precipitation. Assuming an average depth of 100 m for Titan's lacustrine
depressions, these could have developed in a few tens of millions of years at
polar latitudes higher than 70{\deg} N and S, and a few hundreds of million
years at lower polar latitudes. The ages determined are consistent with the
youth of the surface (<1 Gyr) and the repartition of dissolution-related
landforms on Titan.
