re: seismic studies?
Viking 1 Lander and Viking 2 lander had seismometers, but Viking 1's didn't work and martian winds made Viking 2's data useless.
The Mars Environmental Survey (MESUR) network would have placed a network of landers on Mars, each with a seismometer. Pathfinder was a test of the design but I don't think it had a seismometer.
