Both Opportunity and Spirit were powered by the 20MHz BAE RAD6000, a radiation-hardened version of the original IBM POWER1 RISC Single Chip CPU and the indirect ancestor of the PowerPC 601. Many PowerPC-based spacecraft are still in operation, both with the original RAD6000 and its successor the RAD750, a radiation-hardened version of the G3.
Meanwhile, the Curiosity rover, which is running a pair of RAD750s (one main and one backup, plus two SPARC accessory CPUs), is still in operation at 2,319 Mars solar days and ticking. There is also the 2001 Mars Odyssey orbiter, which is still circling the planet with its own RAD6000 and is expected to continue operations until 2025. Curiosity's design is likely to be reused for the Mars 2020 rover, meaning possibly even more PowerPC design will be exploring the cosmos in the very near future.