The CPU on board is a RAD750: http://en.wikipedia.org/wiki/RAD750 It is a radiation hardened PowerPC 750. The PowerPC 750 was launched in 1997 and the RAD 750 in 2002. So, it looks like radiation hardening took 5 years.
The MSL project started in 2004. So, it was probably the best radiation hardened processor for the job at the time.
The MSL project started in 2004. So, it was probably the best radiation hardened processor for the job at the time.