The soft soil exposed when wheels of NASA's Mars Exploration Rover Spirit dug into a patch of ground dubbed "Troy" exhibit variations in hue visible in this image, in which the colors have been stretched to emphasize the differences.
Spirit used its panoramic camera during the 1,892nd Martian day, or sol, of the rover's mission on Mars (April 29, 2009) to take the three images combined into this composite image. The three images were taken through filters centered at wavelengths of 750 nanometers, 530 nanometers and 430 nanometers. Spirit had become embedded at Troy by about a week later.
The two rocks near the upper right corner of this view are each about 10 centimeters (4 inches) long and 2 to 3 centimeters (1 inch) wide.