One strength of Field D* is that it is computationally efficient, Stentz said. Crusher, for instance, can produce new path plans several times a second. But the computers onboard Spirit and Opportunity are only about one-hundredth as fast as a typical desktop computer, far less powerful than the processors onboard Crusher. So in spring 2005, Stentz and Ferguson, now a research scientist at Intel Research Pittsburgh, began adapting Field D* to run on a weaker processor. They delivered it to JPL, where Carnegie Mellon alums Mark Maimone and Joseph Carsten, along with technical staff member Arturo Rankin, integrated it into the Mars Exploration Rover software.