ScienceMag has a short report on a new theory presented at the American Geophysical Union meeting that the gullies leading down the slopes of dunes each Martian spring (see image at link) may be caused by surfing chunks of dry ice.
During the Martian winter, carbon dioxide ice freezes over parts of the planet’s surface and sublimates back into a gas during the spring thaw. But according to the model, chunks of warming dry ice may also break off from the crests of dunes and skid down slopes. This is no ordinary tumble; the bases of the chunks are continually sublimating, resulting in a hovercraft-like motion that gouges the dune while propelling the ice down slopes.
This theory explains why no rocks were ever seen at the bottom of the gullies, and no alluvial fan appeared at the bottom. Experiments in similar land forms in Utah show similar patterns of gullies getting smaller as they go down hill.
The presentation took place at the on going Fall meeting of the American Geophysical Union and have not been published yet.
(Score: 2) by dlb on Wednesday December 17 2014, @06:20AM