The semi-circular depression on the right side of this microscopic image resulted from Opportunity's first grinding of a rock on Mars. The rock abrasion tool sliced into the surface about 4 millimeters (0.16 inches) deep and ground off a patch 45.5 millimeters (1.8 inches) in diameter on a rock called "McKittrick" during Opportunity's 30th sol on Mars, Feb. 23, 2004. The hole exposed fresh interior material of the rock for close inspection by the rover's microscopic imager and two spectrometers on the robotic arm.
Scientists and engineers got a nice bonus in that two spherical features nicknamed "blueberries" were unexpectedly cut in half within this rock. Team members had noticed the blueberries in earlier pictures on other rocks in the outcrop and had wanted to attempt to cut one in half sometime during the future of the mission. As luck would have it, two blueberries were hidden in the depths of "McKittrick." The one blueberry shown in the bottom right of this picture appears to have been scratched by the grinding wheel, which is further explained in PIA05446.
The two rectangular boxes in the lower left and upper middle parts of this image are "drop outs," where the data packets inadvertently did not make it back to Earth during the initial communications relay via the Deep Space Network antennas. The missing data packets should be resent to Earth within the next few days. Just above each of the black "drop out" rectangles is another rectangular area filled with a cluster of smaller rectangles in different shades of gray, which are image compression artifacts.
For more information about the "blueberries," please see JPL's Press Release dated February 9, 2004.
For more microscopic images of the results from Opportunity's first use of the rock abrasion tool, please see the raw images for sol 30.
The rock abrasion tools on both Mars Exploration Rovers were supplied by Honeybee Robotics, New York, N.Y.