Aram Chaos on Mars Created by Collapse of Ice Lake

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 kilometer wide and four kilometer 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 kilometers 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-kilometer 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 kilometers of liquid water was four times the volume of Lake Baikal, the largest freshwater lake on Earth. The water carved a valley of 10 kilometers wide and 2 kilometers deep in about one month and a chaotic pattern of blocks was left in the Aram crater.

"An exciting consequence is that rock-ice units are possibly still present in the subsurface. These never achieved the melting conditions, or melted only a lower thin layer, insufficient to result in a full collapse event. Buried ice lakes testify of Mars rapidly turning into a cold, frozen planet, but with lakes buried in the subsurface. These lakes could provide a potentially favorable site for life, shielded from hazardous UV radiation at the surface," said Roda.

The study was carried out by Roda and colleagues Tanja E. Zegers, Maarten G. Kleinhans and Rob Govers from Utrecht University and Jelmer H.P. Oosthoek of Jacobs University Bremen.

Media Contacts:
Anita Heward
EPSC 2013 Press Officer
+44 (0)7756034243
anitaheward@btinternet.com

Oli Usher
Communications Manager, MAPS Faculty, UCL
+44 (0)20 7679 7964
o.usher@ucl.ac.uk

Monique Westrik
Utrecht University, Marketing & Communications Department
m.westrik@uu.nl

Evelien Harmsen
Utrecht University, Marketing & Communications Department
e.harmsen@uu.nl

EPSC 2013 Press Office (9-13 September only)
+44 (0)207 679 3461 / +44 (0)207 679 0469

Science Contacts:
Manuel Roda
Utrecht University, Faculty of Geosciences
m.roda@uu.nl

Maarten Kleinhans
Utrecht University, Faculty of Geosciences
m.kleinhans@uu.nl

Images

http://www.europlanet-eu.org/images/stories/epsc2013/roda1.jpg
Figure 1 -- View of Aram Chaos with elevation map. Aram Chaos is an impact crater on Mars. It is connected to Ares Vallis by a 10 km wide and 2 km deep outflow channel.

http://www.europlanet-eu.org/images/stories/epsc2013/roda2.jpg
Figure 2 -- Melting process: Numerical modeling shows how the internal heat of the planet diffuses up into the crater with the ice layer. The 273K line indicates the melting point. After roughly 280 million years the sediment layer on the ice has become so thick that the water melts. The layer of rock on top of fluid water is unstable and would have broken up in reality.

http://www.europlanet-eu.org/images/stories/epsc2013/roda3.jpg
Figure 3 -- Prospective view of Aram Valley inlet The Aram Valley is a deep (2 km) V-shaped valley which connects Aram Chaos to the Ares Vallis. Credit: http://google.com/mars (Vertical exaggeration 3)

http://www.europlanet-eu.org/images/stories/epsc2013/roda4.jpg
Figure 4 -- Artist's impression of the chaotization event in Aram Chaos. Credit: Faculty of Geosciences, Utrecht University

About the European Planetary Science Congress (EPSC):
EPSC is the major European meeting on planetary science. EPSC 2013 is taking place at University College London (UCL) from Sunday 8 September to Friday 13 September 2013. It is the first time that the Congress has been held in the UK. The 2013 program includes around 75 sessions and workshops. Details of the Congress and a full schedule of EPSC 2013 scientific sessions and events can be found at the official website:
http://www.epsc2013.eu/

EPSC 2013 is organized by Europlanet, UCL and Copernicus Meetings and the event is sponsored by the UK Space Agency, UCL, Astrium and the Science and Technology Facilities Council. To celebrate EPSC coming to London, a 'Festival of the Planets' has been organized across the Capital in collaboration with partners including the Baker Street Irregular Astronomers, the Bloomsbury Theatre, the British Astronomical Association, the British Interplanetary Society, the Natural History Museum, the Open University, Queen Mary University of London, the Royal Astronomical Society, Royal Museums Greenwich and University College London. http://www.europlanet-eu.org/epsc2013/outreach-activities

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