LOS ANGELES - Microscopic photographs of a Mars rock taken by NASA (news - web sites)'s Opportunity rover have triggered excitement among scientists, even if they aren't unanimous on exactly what they're seeing. The images, posted on Jet Propulsion Laboratory's Mars rovers Web site, show a highly detailed surface on a rock dubbed "El Capitan" that has been undergoing examination by the robot geologist. "They are just very beautiful things and it's not at all clear that we understand what we're looking at," mission official Rob Manning said in a teleconference with reporters on Monday. "There is a lot of...