Free Astronomy Magazine January-February 2016

O n the left, area around High Dune, the first Martian dune studied up close as from end-Novem- ber. This territory is part of the active dunes complex called Bagnold Dunes, along the northwestern slopes of Mount Sharp, in- side Gale Crater. Also in this case, the colours and light- ing conditions simulate a terrestrial environment. [NASA/JPL-Caltech/MSSS] along the northwestern flanks of Mount Sharp, the rover finally reached an area with spectacular sand dunes up to 6-7 me- tres high, very similar to those of terrestrial des- erts. It is the first time ever that structures of this type are being observed so closely. So far had been visited only undulations similar in appearance but much lower, such that they cannot be defined dunes, term used for indicating conformations which have a downwind face suffi- ciently steep to allow the sand of which they are composed to slide down. The area reached by Cu- riosity had been (infor- mally) named Bagnold Dunes, in honour of Ralph Alger Bagnold, British army offi- cer and engineer, who had been a pioneer in the study of the ef- fects of wind on the migration of the dunes’ sand grains. The study of these Mars structures has many interesting aspects. One in par- ticular is the fact that they are still active, in that they are mov- ing about 1 metre every Earth year, as shown by careful obser- vations made with the High Res- PLANETOLOGY A bove, a shal- low layer of Martian sand, located at High Dune. The sand has been loose- ned by a wheel of Curiosity to ex- pose the under- lying material, containing a com- ponent of fine sand that on the