Artist’s impression of the chaotization event in Aram Chaos. (Credit: Faculty of Geosciences, Utrecht University)

Sep. 13, 2013 — Aram Chaos, the lumpy, bumpy floor of an ancient impact crater on Mars, formed as a result of catastrophic melting and outflow of a buried ice lake. A new study combines observations from satellite photos of the 280 kilometre wide and four kilometre deep crater plus models of the ice melting process and resulting catastrophic outflow. Manuel Roda has presented the results at the European Planetary Science Congress (EPSC) at UCL in London.

Chaotic terrains are enigmatic features, stretching up to hundreds of kilometres across, that are distinctive to Mars. The mechanism by which they formed has been poorly understood by scientists.

"About 3.5 billion years ago, the pristine Aram impact crater was partly filled with water ice that was buried under a two-kilometre thick layer of sediment. This layer isolated the ice from surface temperatures, but it gradually melted over a period of millions of years due to the heat released by the planet. The sediment overlying fluid water became unstable and collapsed," said Roda.

The resulting massive expulsion of a hundred thousand cubic kilometres of liquid water was four times the volume of Lake Baikal, the largest freshwater lake on Earth. The water carved a valley of 10 kilometres wide and 2 kilometres deep in about one month and a chaotic pattern of blocks was left in the Aram crater.

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