Rover Prepares to Explore More of Mars   

The Opportunity rover temporarily stowed its robotic arm and cleared a six-inch bump on its way to taking another bite out of the martian surface, NASA said.  Over the weekend, the six-wheeled robot ground into the upper part of a rocky outcrop dubbed "El Capitan," then take extensive measurements, NASA said late Friday. Last week, the rover drilled into a different section of the glossy formation that has intrigued scientists.  "El Capitan" has been the rover's primary interest for several days. The outcrop, about the height of a street curb, rings a portion of the crater in which the robot is maneuvering.

Previous microscopic images revealed fine layering in the rock and mysterious BB-sized granules that could be significant as the rover searches for signs that water has existed on the planet. Scientists involved in the $820 million Mars mission are weighing several theories of how the rock formed, including volcanic eruptions, windblown dust and sediments settling out of a body of water.

Halfway around Mars, Opportunity's twin, Spirit, made its final approach to "Humphrey," an imposing rock that the rover will analyze.  Scientists expect Spirit to reach the rim of the so-called "Bonneville" crater by mid-March.

FMI: www.nasa.gov