The latest images released by NASA’s HiRISE (High Resolution Imaging Science Experiment) team show ‘Morse code’ dunes on the Martian surface.
‘Morse code’ dunes on Mars. Image credit: NASA / JPL / University of Arizona.
The images were captured in February 2016 by the HiRISE camera, an instrument aboard NASA’s Mars Reconnaissance Orbiter (MRO).
The shape and orientation of dunes can usually tell us about wind direction, but in the HiRISE images, the dune-forms are very complex, so it’s difficult to know the wind direction.
A circular depression — probably an old impact crater — has limited the amount of sand available for dune formation and influenced local winds.
As a result, the dunes here form distinct ‘dots’ and ‘dashes.’
Martian dune field. Image credit: NASA / JPL / University of Arizona.
The dashes are linear dunes formed by bi-directional winds, which are not traveling parallel to the dune.
Instead, the combined effect of winds from two directions at right angles to the dunes, funnels material into a linear shape.
The dots – known as barchanoid dunes — occur where there is some interruption to the process forming those linear dunes.
This process is not well understood at present and is one motivation for members of the HiRISE team to image this area.
