After a reboot of its computer, which can be considered the rest and recuperation needed for machines.
This rover is obviously well built given the fact that it's still operational for over 10 years, without any physical maintenance from NASA employees. http://www.universetoday.com/114595/repaired-opportunity-rover-readies-for-marathon-valley-as-it-transmits-martian-images/ http://www.universetoday.com/114595/repaired-opportunity-rover-readies-for-marathon-valley-as-it-transmits-martian-images/
