Jul 222015
This got lost in all the excitement over New Horizons/Pluto a week ago. But July 15 was the 50th anniversary of the Mariner 4 probe’s flyby of the planet Mars. Not only was this the first flyby of Mars, this was the *end* of “Mars.” prior to Mariner 4, people could at least imagine that the atmosphere, while thin, could support life, that there would be some amount of liquid water on Mars, perhaps even vegetation and canals. But Mariner 4 showed that Mars had an atmosphere not 1/4 as thick as Earth’s, but more like 1/150th as thick, that there was no possibility of liquid water (and little enough frozen water), and no vegetation or canals. More than a few science fiction authors of the day were a bit disappointed.