Areology is the
study of the
planet Mars, the "Martian equivalent of
geology," as geocrawler.com phrased it. It comes from
Ares, the Greek god of
war and equivalent of the Roman god Mars after whom the planet is named. The
Oxford English Dictionary has citations for this word starting in
1881;
science fiction writers have been using it at least since
1932, but most of the citations found via Google have to do with actual
space exploration.
Sources:
http://wordsmith.org/awad/archives/0903
http://www.jessesword.com/SF/sf.shtml
http://kosmoi.com/Science/Geology/
http://www.geocrawler.com/archives/3/3389/2002/3/0/8079087/
http://geology.about.com/cs/mars/