Sand on Mars

13 Oct 2017

The origin of sand on earth has intrigued Gary Gilligan for a number of years. He sent in the link www.dailymail.co.uk/sciencetech/article-4967664/NASA-image-reveals-possi... ... but see also https://phys.org/print426924999.html ... an image from NASAs Mars Reconnaissance Orbiter shows one place where sand grains are potentially being produced on Mars - right now. Note the word potential - scientists are looking for the source of sand dunes on Mars and for the moment have tuned their sights on this depression ...

   ... the image shows dark material is being eroded from layers of bedrock in what looks like a deep depression on the surface. Wind blown sand, we are told, is lifted above the surface of Mars (going by geological concepts of sand erosion on Earth) and crashes back down again, bouncing in a sequence of hops known as saltation. As these bounces impact with the ground the sand grains are said to wear down - and somewhat later eventually become spherical in shape (much like pebbles on the beach eroded by wave action). There are extensive sand dunes on Mars and scientists are seeking an origin for all that sand. The connection between the two are conjecture but you can bet your last dollar that it will become the preferred explanation and be trotted out repeatedly in subsequent reports from Mars. The point is that sand dunes on Mars today implies sand particles are being supplied to replenish the dunes.