Chaos terrain generally consists of irregular groups of large blocks, some tens of kilometers across and a hundred or more meters high.
[1] A chaotic region can be recognized by a rat's nest of mesas, buttes, and hills, chopped through with valleys which in places look almost patterned.
[7][8] Most of the chaotic terrain exists in the highlands of Mars, south of Chryse Planitia, in the Oxia Palus quadrangle, and along the Martian dichotomy.
Some researchers have suggested that a frozen layer, called a cryosphere, developed over a long time period and then something triggered it to rupture and melt suddenly.
The rupturing event may have been impacts,[10] magma movements,[11][12] seismic activity,[13] volcanic tectonic strains,[14] increased pore pressure, or the dissociation of clathrates.
[20] Later proposals advanced the notion that the geological shapes present in chaos regions could have been made by a series of over 100 flooding events.
Tanja Zegers and others calculated that the simple burial of ice-rich sediments could result in the release of huge amounts of water leading to the formation of the large river basins that are associated with most chaos terrains.
[22] There is ample evidence for buried deposits of ice in the form of glaciers, preserved under a thin covering of rock and dirt.
[28][29] Research, published by Rodriguez and others in 2005, suggested that the subsurface of Mars contains an accumulation of old craters that may be filled with water or ice.
Research by Pedersen and Head, published in 2010, suggests that Galaxias Chaos is the site of a volcanic flow that buried an ice-rich layer, called the Vastitas Borealis Formation (VBF).
On April 1, 2010, NASA released the first images under the HiWish program in which just plain folk suggested places for HiRISE to photograph.