Aram Chaos is a roughly circular depression approximately 280 kilometres in diameter in the Arabia Terra region of Mars. It is classified as a "chaotic terrain" - a type of Martian landform characterised by irregular mesas, knobs and fractured bedrock that formed when the ground beneath collapsed.
How chaotic terrains form
The accepted model for chaotic terrain formation on Mars involves the catastrophic release of subsurface water. Mars once had substantial quantities of water stored as ice in its subsurface. When this ice melted - triggered by volcanic heating, impact energy, or changes in the Martian climate - it could drain away rapidly, leaving the overlying rock unsupported. The ground then collapsed, creating the jumbled terrain of mesas and fractured blocks visible in Aram Chaos.
The water released by this process had to go somewhere. Outflow channels extending from chaotic terrains toward the northern lowlands of Mars provide the evidence: Aram Chaos is connected to Ares Vallis, a major outflow channel that transported catastrophic floods northward across the Martian surface. The volume of water involved was comparable to terrestrial oceans.
Why Aram Chaos is scientifically important
The Opportunity rover was targeted to land in Meridiani Planum partly because of its proximity to Aram Chaos - the region's geological history of water made it a promising location to look for evidence of past habitability. The subsequent discovery of haematite "blueberries" by Opportunity confirmed that liquid water had once been present.
The Axisophy print
The HiRISE image shows Aram Chaos at a resolution where individual blocks of fractured rock are distinguishable. The chaotic texture - irregular mesas separated by low-lying troughs - reads as an abstract field at normal viewing distance.
