The pictures, released Tuesday, show a coin-sized patch of grainy soil, peppered with tiny pebbles. Opportunity captured the images with its microscopic imager, one of four instruments at the end of its robotic arm.

Opportunity and its twin, Spirit, began this week conducting what NASA hoped would be sustained science operations. The rovers, 6,600 miles apart, both reached out with their mechanical arms to study firsthand the soils and rocks on the ground beneath their wheels.

Opportunity rolled onto the ground Saturday, a week after it landed. Spirit arrived Jan. 3 but a couple of weeks later it was sidelined with software problems.

Mission manager Jennifer Trosper said Spirit returned to work, even as engineers worked out the final kinks in the software.

Opportunity has transmitted its first 360-degree color panoramic image of its landing site. The rover touched down in one of the flattest, smoothest regions on Mars but ultimately came to rest inside a crater just 72 feet across.

"It provides us with a real sense of 'you are there,'" said scientist Jeff Johnson of the U.S. Geological Survey office in Flagstaff, Ariz. Johnson likened the mosaic image to the overlapping snapshots tourists often take of the Grand Canyon to capture its full sweep.

The National Aeronautics and Space Administration next planned for Opportunity to put its Mossbauer spectrometer to the ground. The German-built instrument measures the composition and abundance of iron-bearing minerals.

Spirit resumed its own scientific observations, and NASA planned for it to brush off the surface of a volcanic rock called Adirondack, removing any dust and allowing the rover's microscopic imager to photograph it.

NASA launched the pair of roaming robots to find geological evidence of past water activity on Mars. That could show the planet was hospitable to life perhaps billions of years ago.

Opportunity hasn't had to venture far to gather evidence.

Halfway around Mars from its twin, the robot already has discovered an iron-rich mineral called gray hematite. Preliminary measurements suggest the mineral is of a variety that forms in liquid water, providing the first hint that the now dry site once was wetter.

NASA announced it would name seven hills east of Spirit's landing site in memory of the astronauts killed a year ago aboard the space shuttle Columbia. The agency must submit the names to the International Astronomical Union for official designation.

NASA previously said it would name another group of hills at the site to memorialize the three Apollo 1 astronauts killed in a launch pad fire in 1967.