Cebrenia Quadrangle - Galaxias Region

Galaxias Region

The ground in Galaxias seems to have collapsed. Such land forms on Mars are called "Chaos terrain." Galaxias Chaos is different from many other chaotic regions. It does not have associated outflow channels, and it does not display a great elevation difference between it and the surrounding land area, as most of the other chaos regions. 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). It is generally believed that the VBF is a residue from water-rich materials deposited by large floods. The VBF may have been of varied thickness and may have contained varied amounts of ice. In the thin atmosphere of Mars, this layer would have slowly disappeared by sublimation (changing from a solid directly to a gas). Since some areas would have sublimated more than others, the upper lava cap would not be supported evenly and would crack. Cracks/troughs may have begun from sublimation and shrinkage along the edges of the lava cap. Stress from the undermining of the cap edge would have made cracks in the cap. Places with cracks would undergo more sublimation, then the cracks would widen and form the blocky terrain characteristic of regions of chaos. The sublimation process may have been aided by heat (geothermal flux) from magma movements. There are volcanoes, namely Elysium Montes and Hecates Tholus, nearby which most likely are surrounded by dikes, which would have heated the ground. Also, a warmer period in the past would have increased the amount of water sublimating from the ground.

• This series of drawings shows a model for the formation of Martian chaos, as proposed by Pedersen and Head 2011 Amount of sublimation is exaggerated to improve understanding. Click on image to see more details.

• Galaxius Mons, as seen by HiRISE. The black line was a section that was not imaged. There are many more details visible on the original image.

• Galaxias Fossae Trough, as seen by HiRISE.

• Galaxias Chaos as seen by CTX. The scene in the next image is a part of this picture.

• Galaxias Chaos as seen by HiRISE.