Search for Life on Mars by Robotic Drilling
In my opinion, it should be possible to develop a fully automated roving Mars laboratory that drills holes, extracts cores, subjects the samples to electron microscopy and many other tests, and STILL costs less than one percent the cost of a manned mission.
Sure, it would weigh several tons, but it would not require food, air conditioning, etc. Most importantly, it would not require another large rocket to get it back home. Only data would be sent back to Earth.
David F Mayer