Free Astronomy Magazine November-December 2015

NOVEMBRE-DICEMBRE 2015 landslides along the walls of some craters, but this does not necessarily imply evi- dence of a recurrent phenomenology and, mostly, that is still taking place. Showing that still today there is flowing water on Mar’s surface would greatly in- crease the chances of discovering in the near future forms of bacterial life, survived to the global drying-up suffered by the planet over billions of years. It is therefore understandable the uproar caused by an article published by some researchers in Nature Geoscience on last 28 September, whom, thanks to observations by NASA’s Mars Reconnaissance Orbiter (MRO), have indirectly shown that, even at present, there is liquid water on the Martian sur- face. The foundations of the new discovery were laid in 2010-2011, when Lujendra Ojha (Georgia Institute of Technology, Atlanta) and Alfred McEwen (Lunar and Planetary Laboratory, University of Arizo- na, Tucson) began to notice in the images taken by the HiRISE (High Resolution Im- aging Science Experiment) instrument of the MRO a few series of dark streaks run- ning along steep slopes, which reach their maximum extent during warmer seasons, to then retreat and disappear during the A bove, RSL extending for several hun- dred metres along the wall of Garni Crater (the vertical scale is exaggerated by 50%). Below, similar forma- tions, about 100 metres long, dis- covered inside Hale Crater. [NA- SA/JPL-Caltech/ Univ. of Arizona]