Practically overnight, an unexplained piece of rock has shown up on photos from NASA's Mars rover Opportunity, according to the digital Russian TV network RT (Russia Today). The rover hasn't moved in over a month, as it waits for better weather, but a photo taken on Sol 3540 (Jan. 8, or the 3,540th Martian solar day since the Opportunity rover landed) shows a rock that wasn't visible in previous photos taken on Sol 3536. ... Staffers at the Jet Propulsion Laboratory in California who maintain the rover camera (pancam) database for NASA have named the rock Pinnacle Island.