Synthetic Aperture Radar (SAR) interferometry (InSAR) has been used to make detailed crustal movement images, showing relative displacements of as small as a few millimetres per year, according to this Envisat ESA PR. Although the PR talks about using InSAR for monitoring seismic zones and volcanos, I wonder if it could also be used for other Earth studies. For example, combined with GRACE results, to better characterise the nature of gravity anomolies? to test some of the alternative theories to GR (such as SCC)? Perhaps the same technology could be deployed on a Venus, Mars, or Io mission, to determine the extent of any crustal movements?