This oval mesa is a remnant of a geological unit that once covered this area, similar to the mesas and buttes in Monument Valley, in Arizona and Utah. This is a small remnant of a much larger unit of similar material that caps Ganges Mensa to the west.
As can be seen in the sides of this small mesa, this remnant consists of a layered stack of rock. Prior to the massive erosion that left this a high-standing mesa, a more gentle phase of erosion created the small hills and whorls on the upper surface of the mesa. It seems that this gentle erosion continued even after the mesa was created, as this pattern of small hills and whorls is visible on the terrain surrounding the mesa.
Although not visible in the area shown in this HiRISE image, this mesa actually sits on top of the much larger Ganges Mensa, which is itself a large mesa within Ganges Chasma.
Written by: Ross Beyer (4 March 2009)
This is a stereo pair with ESP_011582_1730 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_011648_1730
Image: NASA/JPL/University of Arizona