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.