Europlanet 2020 RI / Open University Press Release
**EMBARGOED until Friday 27 October 2017, 10:00 BST (09:00 UTC) **
Levitation key to long-debated mystery of how recent and present-day martian landscapes form
Scientists from The Open University (OU) have discovered a process that could explain the long-debated mystery of how recent and present-day surface features on Mars are formed in the absence of significant amounts of water.
Experiments carried out in the OU Mars Simulation Chamber – specialised equipment that is able to simulate the atmospheric conditions on Mars – reveal that Mars’s thin atmosphere (about 7 mbar – compared to 1,000 mbar on Earth), combined with periods of relatively warm surface temperatures, causes water flowing on the surface to boil violently. This process can then move large amounts of sand and other sediment, which effectively ‘levitate’ on the boiling water. This means that relatively small amounts of liquid water moving across Mars’s surface could form the large dune flows, gullies and other features that characterise the Red Planet.
Jan Raack, Marie Skłodowska-Curie Research Fellow at The Open University and lead author of the research, said: “Whilst planetary scientists already know that the surface of Mars has features such as dune flows, gullies and recurring slope lineae that occur as a result of sediment transportation down a slope, the debate continues about what is forming these recent and present-day active features. Our research has discovered that the levitation effect caused by boiling water under low pressure enables the rapid transport of sand and sediment across the surface. This is a new geological phenomenon that doesn’t happen on Earth, and could be vital to understanding similar processes on other planetary surfaces.”
Raack conducted these experiments in the Hypervelocity Impact (HVI) Laboratory based at the OU. He added: “The sources of this liquid water will require more observational studies; however, the research shows that the effects of relatively small amounts of water on Mars in forming features on the surface may have been widely underestimated. We need to carry out more research into how water levitates on Mars, and missions such as the ESA ExoMars 2020 Rover will provide vital insights to help us better understand these processes on our closest planetary neighbour.”
The research, which has been published on Friday 27 October 2017 in the academic journal Nature Communications, is funded by the Europlanet 2020 Research Infrastructure through the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No 654208, and co-authored by academics* from the STFC Rutherford Appleton Laboratory, Universität Bern, and Université de Nantes. The initial research concept was developed by Susan J. Conway of Université de Nantes.
*The research, ‘Water induced sediment levitation enhances downslope transport on Mars’, was developed in collaboration with the following academics:
Jan Raack (lead author), Manish R. Patel, Matthew R. Balme – School of Physical Sciences, Faculty of STEM, The Open University, Milton Keynes
Clémence Herny – Physikalisches Institut, Universität Bern, Switzerland
Sabrina Carpy, Susan J. Conway – Laboratoire de Planétologie et Géodynamique, Université de Nantes, France.
After the embargo expires, the paper will be available at: https://www.nature.com/articles/s41467-017-01213-z
On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: “levitation” of saturated sediment bodies on a cushion of vapour released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought.
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