In the Human Vs Machine debate, if the purpose is science, machines are better value. A human would only use fancy instruments anyway, so they might as well control the instruments from back on earth or via software.
A machine can stay so much longer. Consider the two
Martian Rovers, Spirit and Opportunity. Despite their 90-martian-day design plan, they have been running for 2,092 and 2,071 days respectively. All this for well under a billion dollars. Love those little tigers.