Free Astronomy Magazine September-October 2018

5 F ew topics in planetary science excite re- searchers and the public more than the discovery of water. To geologists and climatologists, liquid water reveals that conditions must lie within some reasonable temperature regime, providing information about the surface and atmosphere. For astrobiologists, liquid water is one of the key requirements needed for life as we know it. Space engineers see liquid water less as the stuff of life as they do the stuff of cost reduction − water in liquid form means a readier source for both propellant and consumption. Among the known water-bearing bodies be- yond Earth, only Mars has combined rapid scientific discovery with public engagement SEPTEMBER-OCTOBER 2018 PLANETOLOGY and technical capability with economic fea- sibility. A recent study of Planum Australe in the southern polar ice cap region using the Mars Advanced Radar for Subsurface and Ionospheric Sounding, or MARSIS, in- strument on the European Space Agency (ESA) Mars Express Orbiter (MEO) reports the detection of what might be an active location of persistent, still-liquid water − although not a body of liquid easily ac- cessible or, for that matter, in a form usable by future colonists. The Italian research col- laboration, led by Roberto Orosei at the Italian National Institute for Astrophysics in Bologna, published the findings of their 12-year study in the July 25 th issue of Science magazine (DOI:10.1126/science.aar7268). T he Mars Express spacecraft used its MARSIS experi- ment to send radio waves down to Mars and interpret the echoes it sent back. Based on the data, scientists be- lieve there is water below the surface of Mars. [ESA]