This image shows blocks of bright, layered rock embedded in darker material that are thought to have been deposited by a giant flood that occurred when Uzboi Valles breached the rim of Holden Crater (Grant et al., 2008, Geology v. 36, p. 195-198).
The magnitude of this ancient flood is indicated by the large size of the blocks (up to 100 meters across). The blocks do not appear to have been moved very far by the flood, as they are not rounded.
Holden Crater is one of the four potential landing sites for the Mars Science Laboratory rover, to be launched in November 2011. The bright layered rock in this image probably contain a record of a wetter, warmer period early in Martian history, and are therefore a prime target for exploration.
Written by: Ken Herkenhoff (20 October 2010)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_019256_1530
Image: NASA/JPL/University of Arizona