Global warming … on Mars?      causing a melting of the polar ice caps, you might think you were hearing about global warming.  And of course, you would be right — just not about earth, but rather Mars instead.  This according to the Heartland Institute, which reports how recent NASA findings confirm that for the past three Martian summers, deposits of frozen CO2 from the Martian south pole have shrunk, indicating a significant planetary warming underway.  Scientists attribute this Martian warming not to any manmade emissions, but to possible increases in the sun’s solar output, which may mean as much as thirty percent of any warming that has occurred on earth could be attributable to this natural cause.