What would the best way be to crash an impactor into Mars with greatest topological effect? And how deep a crater could it excavate?
Mars missions to date have been designed to approach the planet at low speed to land or enter orbit. How would a mission to hit it at maximum speed and mass be designed? Would a Krafft-Ehricke style gravity assist turnaround about Jupiter be the best way? What should the proportions of fuel to impact mass be in the launched payload? Does it matter whether the payload consists out of solid tungsten or a fusion bomb? Assume a single of today's launchers or a Saturn V at most.
The motivation could be to then land science probes in that fresh crater of the underworld of Mars, but that's not the issue here. Just how it could be done if it were assumed to be wished for as the next mission to Mars today.