What software language was used to program the martian rovers Spirit, Opportunity and Curiosity?
Also, how many engineers were involved in writing the software for the rovers?
Almost all in C on the rover computer. On MSL, some of the C was generated automatically using UML state charts. I don't know the exact team sizes. On the order of 20 on MER and 40 on MSL for the flight software on the rover computer. You would also need to consider the software on the instruments. And the radio. And the motor controllers.
Lots of good stuff in the answers to this question.
Many different languages are used in the ground software.