OUTER PLANETS

   Relatively little attention has been paid in sf to the planets beyond Jupiter. Of them only Saturn was known to the ancients - Uranus was discovered in 1781, Neptune in 1846 and Pluto in 1930 - and it is therefore the only outer planet featured in Athanasius KIRCHER's and Emanuel SWEDENBORG's interplanetary tours. Uranus, however, is included inthe anonymous Journeys into the Moon, Several Planets and the Sun: History of a Female Somnambulist (1837). The only object beyond Jupiter that has made significant appeal to speculative writers as a possible abode for life is Saturn's major moon Titan, though the fascinating rings have provoked a good deal of interest from interplanetary passers-by. Pluto has come in for a certain amount of special attention as the Ultima Thule of the Solar System, although as much - if not more - interest has been shown in the possibility of there being a 10th planet even further out.Saturn was visited, en route to Earth, by VOLTAIRE's tourist from Sirius in Micromegas (1750; 1952), and a Saturnian accompanied him on hissightseeing trip. It was one of the major worlds featured in J.B. Fayette's anonymously published The Experiences of Eon and Eona (1886);and in John Jacob ASTOR's A Journey in Other Worlds (1894) it is the home of the spirits, who confirm the truth of the theological beliefs of travellers from a future Earth. Roy ROCKWOOD's series of juvenile interplanetary novels extended thus far in By Spaceship to Saturn (1935), but relatively few PULP-MAGAZINE writers followed suit. Arthur K. BARNES's Interplanetary Hunter (1937-46; fixup 1956) ventured beyond Jupiter on twooccasions, but Stanley G. WEINBAUM was the only early pulp writer of any real significance to explore the outer planets, in "Flight on Titan" (1935), "The Planet of Doubt" (1935) - one of the rare stories set onUranus - and "The Red Peri" (1935), a SPACE OPERA set partly on Pluto. Other pulp stories set in the outer reaches include J.M. WALSH's "The Vanguard to Neptune" (1932), Wallace WEST's "En Route to Pluto" (1936), Raymond Z. GALLUN's "Raiders of Saturn's Rings" (1941) and Murray LEINSTER's "Pipeline to Pluto" (1945). One of Stanton A. COBLENTZ's SATIRES, Into Plutonian Depths (1931; 1950), delved there, and Clifford D. SIMAK's Cosmic Engineers (1939; rev 1950) begins near Pluto. By far and away the most significant role allotted to an outer planet in the speculative fiction of the pre-WWII period was, however, that given to Neptune by Olaf STAPLEDON in LAST AND FIRST MEN (1930) and Last Men inLondon (1932): in the very FAR FUTURE, the ultimate members of the human race are forced to make a new home there following the expansion of the Sun.In the post-WWII period the outer planets occasionally featured inmore serious speculative fictions. The rings of Saturn play a key part in Isaac ASIMOV's "The Martian Way" (1952), and Asimov returned to the samelocale in his juvenile Lucky Starr and the Rings of Saturn (1958) as by Paul French. Another notable juvenile in which Saturn is an abode of lifeis Philip LATHAM's Missing Men of Saturn (1953). Elsewhere, Titan features much more prominently than its parent world. Alan E. NOURSE's Trouble on Titan (1954) is a juvenile novel about COLONIZATION of the satellite, theclimactic scenes of Kurt VONNEGUT Jr's THE SIRENS OF TITAN (1959) take place there, and Titan is the location of huge ALIEN machines in Ben BOVA's As on a Darkling Plain (1972). A more fully described colony isfeatured in Arthur C. CLARKE's Imperial Earth (1976), and it is the home of the strange lifeform that provides the climax of Gregory BENFORD's and Gordon EKLUND's If the Stars are Gods (fixup 1977). An artificial worldhidden among the satellites of Saturn is the main locale of John VARLEY's Gaean trilogy begun with Titan (1979).Pluto figures prominently in AlgisBUDRYS's Man of Earth (1958), and is the destination of the characters in Wilson TUCKER's To the Tombaugh Station (1960). It is the setting of Kim Stanley ROBINSON's mysterious artefact in Icehenge (1984), and the starting-point of the interplanetary tour featured in the same author's The Memory of Whiteness (1985), which zooms past Uranus and Neptune atconsiderable narrative pace. Neptune's moon Triton is the setting of Margaret ST CLAIR's "The Pillows" (1950) and Samuel R. DELANY's "ambiguousheterotopia" in Triton (1976). The "outer satellites" conduct a war against the inner planets in Alfred BESTER's Tiger! Tiger! (1956 UK; rev vt The Stars My Destination US), but the reader never gets to visit them; a much more detailed conflict takes place in Cecelia HOLLAND's Floating Worlds (1976), in which the cities of the title float above Saturn andUranus. Few of those space operas whose action is partly set in the more remote regions of the Solar System pause to take in much of the scenery, but notable recent exceptions include Colin GREENLAND's TAKE BACK PLENTY (1990) and Roger McBride ALLEN's The Ring of Charon (1990), both of whichare partly set on Pluto's large moon Charon.It has long been held in some quarters that a 10th planet is necessary to account for the orbital perturbations of Uranus, even after Neptune and Pluto are taken into account, and sf writers have occasionally dealt with the possibility. The protagonists of John W. CAMPBELL Jr's The Planeteers (1936-8; coll of linked stories 1966) ultimately make their way there, and it is the setting for Henry KUTTNER's "We Guard the Black Planet" (1942). In Philip K. DICK's SOLAR LOTTERY (1955; vt World of Chance) members of an esotericcult flee Earth in the hope of finding such a world. Edmund COOPER's The Tenth Planet (1973) plants an advanced civilization there. Contrastingly,in Lucifer's Hammer (1977) by Larry NIVEN and Jerry POURNELLE it is a much more remote GAS GIANT, whose gravity perturbs the orbit of a comet, deflecting it towards Earth. Perhaps more intriguing than the notion of a 10th planet is speculation about the Solar System's diffuse cometary"halo". An extravagant sf version of this is developed in The Reefs of Space (1964) by Frederik POHL and Jack WILLIAMSON, which features a particularly imaginative reef life-system. Clarke's Imperial Earth makes much of the possibility of life existing beyond Pluto, and Williamson made further use of the locale in Lifeburst (1984).More recently, there has been discussion among astronomers of the possibility that the cause of the orbital perturbations among the outer planets might instead be another star a couple of light years away; i.e., that the Sun might be not a singleton star but one element of a widely spaced binary (most stars are multiple rather than solitary), the other component being a dwarf star, a NEUTRON STAR or even a BLACK HOLE. Even a dwarf star would, at such adistance, be insignificant enough in our skies to make identification difficult. Or the cause might be a yet undetected nearby star heading in our direction, as suggested in Asimov's Nemesis (1989).

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