MERCURY

   Mercury is the planet nearest the Sun, and hence is difficult to observe. Until the late 19th century it was believed to rotate on its axis every 24 hours or so, but this opinion was displaced by that of Giovanni Schiaparelli (1835-1910) and Percival Lowell (1855-1916), who contendedthat it kept the same face permanently towards the Sun. 20th-century sf writers thus pictured it as having an extremely hot "dayside", a cold "nightside" and a narrow "twilight zone". This image persisted until the1960s, when it was discovered that Mercury rotates on its axis rapidly enough to have a day somewhat shorter than its year.The earliest visit to Mercury was probably that of Athanasius KIRCHER in his ItinerariumExstaticum (1656), and it was generally included in other round tours of the planets, including Emanuel SWEDENBORG's The Earths in Our Solar System (1758) and George GRIFFITH's A Honeymoon in Space (1901). John MUNRO's ATrip to Venus (1897) includes a detour to Mercury. The earliest novel in which Mercury came into principal focus was Relation du Monde de Mercure (1750 France) by Le Chevalier de Bethune; the first novel in English to beset there was William Wallace COOK's SATIRE Adrift in the Unknown (1904-5; 1925). E.R. EDDISON's series of fantasy novels begun with The WormOuroboros (1922) is likewise set on Mercury, but the name is used purely for convenience. GENRE SF rarely employed Mercury as a milieu for exotic adventure, preferring MARS and VENUS, but it does feature in Homer Eon FLINT's "The Lord of Death" (1919; in The Lord of Death and the Queen of Life (coll 1965), Ray CUMMINGS's Tama of the Light Country (1930; 1965) and its sequel Tama, Princess of Mercury (1931; 1966), and Clark Ashton SMITH's "The Immortals of Mercury" (1932). An invasion from Mercury isthwarted in J.M. WALSH's Vandals of the Void (1931), and Leigh BRACKETT set one of her exotic romances there, "Shannach - the Last" (1952). Attempts to use Mercury in more thoughtful stories with some fidelity toastronomical knowledge were likewise infrequent in the pre-WWII pulps, the first significant examples being Clifford D. SIMAK's "Masquerade" (1941; vt "Operation Mercury") and Isaac ASIMOV's "Runaround" (1942).After WWII, however, things picked up a little. Three juvenile novels featuring Mercury are Lester DEL REY's Battle on Mercury (1956 as by Erik van Lhin),Asimov's Lucky Starr and the Big Sun of Mercury (1956 as by Paul French; vt The Big Sun of Mercury), and Mission to Mercury (1965) by Hugh WALTERS. Alan E. NOURSE's memorable "Brightside Crossing" (1956) represents ajourney across the dayside of the planet as an adventurous feat akin to the then-recent conquest of Everest. The nightside of Mercury features ironically in Larry NIVEN's "The Coldest Place" (1964), but recent sf usually employs Mercury as merely a convenient place to site bases for studying the SUN, like the one in David BRIN's Sundiver (1980). Perhaps the most enduring sf image of Mercury, though, is from Kurt VONNEGUT Jr's THE SIRENS OF TITAN (1959), which offers an account of the Harmonia,cave-dwelling lifeforms thriving on vibration and introduced to music by a stranded astronaut.

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