The equivalent for Mars of a geologist. The word is formed from the prefix areo-, derived from the name of the Greek god of war, Ares, plus the suffix -ologist. It is a term very much of the moment, following the much-publicised claim earlier this year that primordial fossils have survived in an Antarctic meteorite that originated in the Red Planet, and because large amounts of investigative hardware are to be thrown at Mars in the next ten years (or, in the case of a recent unfortunate Russian rocket, not). So it is surprising to discover that the related term areology is first attested by the Oxford English Dictionary in 1881, even before H G Wells had entertained an earlier generation with descriptions of ravaging Martians. Until it turned up in the Economist the other week, almost the only sightings of areologist have been in science-fiction works, notably the Mars trilogy of Kim Stanley Robinson, in which he creates a number of other neologisms in areo-, including areophyte, areosynchronous and areobotany.