I'm curious whether anyone has completed this contract. If so, at what distance from the seismic sensor did you hit the surface? Also, what was the the mass and speed of your craft on surface impact? Did you get the pointy end down and was it under power?
My first attempt was pretty lame - floated down slowly and hit 20 km away. I did get a message from the sensor to the effect that there had been no effect.
I am, of course, in the process of trying again. (And have had no problem with this type of contract on other planets/moons)