According to NASA, "Curiosity is now operating on its B-side, as it did during part of the flight from Earth to Mars."[0] Presumably, it retained some programm

According to NASA, "Curiosity is now operating on its B-side, as it did during part of the flight from Earth to Mars."[0] Presumably, it retained some programming for recovery (as a backup) from the flight, and they didn't have an exact replica of the software A-Side had on B-Side. That being said, they probably have debugging/test software on which ever is serving as the backup computer in order to diagnose and fix the other one in the event of a problem. [0]: http://www.jpl.nasa.gov/news/news.php?release=2013-078 http://www.jpl.nasa.gov/news/news.php?release=2013-078