Planetary Cartography Research Paper

Amphitrite is portrayed in one simple sketch map, and the only published map of asteroid 1 Ceres is an illustration in a science fiction magazine. If Amphitrite is included but Ceres is not, 60 bodies in the solar system have been mapped in a scientific sense. When should a world be said to be mapped? It is accepted for this research paper that composites of multiple observations or images augmented with feature names or other in- formation can be called maps, but not primary observational records (photographs or drawings).

The history of cartography can be portrayed as a linear evolution driven by successive developments in theory, technology and exploration, with modern scientific mapping as its zenith. Planetary cartography is particularly susceptible to this approach. Recent work (e.g., Harley and Woodward 1987) recognizes maps once dismissed as irrelevant and broadens the field to consider uses or aspects of maps overlooked in purely technical histories. Here both approaches are combined, useful references identified and areas indicated that will repay further study, for no comprehensive survey of this subject has yet been undertaken.

1. Background

The International Astronomical Union (IAU) oversees body and surface feature nomenclature, the definition of north and the locations of prime meridians, and publishes its decisions in its Transactions. Surface feature locations are determined by establishing a control network of points measured in multiple images of a world. Greeley and Batson (1990) summarize these technical issues. Many mapped bodies are near-spherical, but where they are not their shapes are estimated from stereoscopic images and the changing outlines of the object in views from different directions.

2. Pretelescopic Planetary Cartography

Markings on the Moon have always been visible, so representations of them are the earliest planetary maps. Drawings by Leonardo da Vinci dated about 1505 were long considered the oldest, but recently other ancient candidates have been suggested. Carvings at Knowth, Ireland (about 2800 BC) may represent the lunar markings, and one at the end of an interior passage might be illuminated at times by the rising Moon. The final form of Stonehenge, a circle containing a double horseshoe, may be a schematic map of the Moon akin to those at Knowth. Its solar alignment is most celebrated, but the full Moon occasionally rises on the monument’s axis. Some Egyptian depictions of the sacred eye representing the Moon resemble the lunar markings. Plutarch gives several lunar place names. Some Arab world maps around AD 1100 resemble the lunar markings in reverse, recalling the ancient belief that the Moon is a mirror reflecting an image of the Earth. Van Eyck painted the Moon with markings in 1430, though they may be merely schematic. William Gilbert drew a lunar map with place names in about 1600, just before the invention of the telescope. Of uncertain age, not ancient but probably drawing on a long tradition, are representations of the maria in native American art, including rock art in the Stein Valley, British Columbia and drawings of the Barasana culture, Colombia. The only other body which could be mapped without a telescope is the Sun, since sunspots had long been known in China, but no such map has ever been described.

3. Telescopic Planetary Cartography

Following the pioneering observations of Harriott and Galileo in 1609, lunar mapping advanced rapidly until the 1800s (Kopal and Carder 1974, Whitaker 1989). Successive cartographers sought mainly to improve accuracy and detail, since the Moon is unchanging. Riccioli’s nomenclature became standard and was formalized by the IAU in the 1930s. Photographs eventually replaced more stylized drawings, culminating in several superb atlases produced under the direction of Gerard Kuiper (University of Arizona) at the dawn of the space age. Frequently overlooked in histories of lunar cartography are maps prepared by and for nonastronomers, such as Homann’s 1720 map comparing the nomenclatures of Hevelius and Riccioli, and numerous small charts shown as insets in celestial or world maps from roughly 1650 to 1800. Some atlases of the 1800s also contain lunar maps. Though rarely more than poor copies of astronomers ’ map, they may have had a wider audience than their models. No systematic study of them has yet been made.

Other worlds were more difficult targets for telescopic observers (Greeley and Batson 1990). The first map of Venus, by Bianchini in 1728, misrepresented faint markings in the planet’s opaque clouds as lands and seas. Similar maps were being drawn until the 1950s. Herschel first mapped Mars in 1783. Schiaparelli in 1877 measured feature locations for positional control, described the spurious ‘ canals ’ which influenced public opinion for decades, and introduced the modern feature nomenclature. The markings of Mars are variable, so maps are made whenever it is well placed for observation (Blunck 1982). Maps of Mercury, beginning with Schiaparelli’s of 1889, were compromised by the assumption of an erroneous rotation period that was not corrected until the 1960s. Markings on the four largest satellites of Jupiter are at the limit of telescopic discernability, but a map was made by Douglass in 1897, and others followed in the 1900s. Ephemeral cloud features in Jupiter’s atmosphere are plotted on what are essentially meteorological maps to monitor changes. Similarly, sunspots and other ephemeral features of the solar photosphere are mapped to record the Sun’s changing appearance. These 10 bodies, excluding Earth, were all that had been mapped before the Space Age.

4. Space Age Planetary Cartography

Spacecraft have visited many worlds since 1959, and like terrestrial explorers these planetary missions generate many maps. Some are used for premission planning, some for operational use during the mission, and others provide a systematic record of discoveries made or activities undertaken. The subject has not yet been described in detail and will form fertile ground for future scholarship.

4.1 Cartography For Lunar Exploration

The Soviet probe Luna 3 photographed the Moon’s far side for the first time in 1959. Later missions filled remaining gaps in coverage and revealed greater detail, permitting large scale mapping of some areas. Landing craft photographed their surroundings, which were mapped at large scales. The US Geological Survey (USGS), Army Map Service, and Aeronautical Chart and Information Center produced over 1,000 maps for the Apollo missions (Kopal and Carder 1974). Astronauts used maps for site selection, training, orbital navigation, and surface activities. In the Soviet Union, MIIGAiK and other agencies produced maps for their lunar missions, including robotic landers and rovers, but never undertook a systematic large-scale mapping program. Lunar mapping in both nations almost ceased in the mid-1970s, leaving a legacy of 1: 250,000 and 1:1,000,000 scale maps as well as global and regional geological maps. Public interest in Apollo resulted in numerous popular maps, atlases, and globes in the 1960s, and for a time many general world atlases included a lunar chart. Most disappeared as interest in lunar exploration waned.

4.2 Cartography For Solar System Exploration

Following Apollo, robotic spacecraft travelled to other planets, all but Pluto having been visited by 1989. In the 1990s several asteroids were explored and other bodies were observed in greater detail. Almost every mission resulted in maps, from systematic geological and topographic mapping by USGS to large-scale charts of the immediate surroundings of landers on Venus or Mars. The Soviet Union attempted no systematic mapping, except at Venus, but its landers gave the only surface views of Venus yet obtained. Mapping by USGS up to about 1994 is summarized by Greeley and Batson (1990). Forty-two worlds had been mapped from planetary spacecraft data by 1999, 20 by USGS. One significant problem concerns small irregularly shaped bodies for which geodetic methods and map projections are still being developed. Many planetary maps since 1990 take the form of digital photomosaics and maps of radar reflectivity, elevation, etc. which may be distributed on CD-ROM or via the World Wide Web, reprojected to any desired map projection and used in Geographic Information Systems. USGS has taken the lead in this, and many such products are now available for free download via NASA’s Planetary Data System. The number of maps published on paper is declining, which will compromise historical studies. Public interest in Mars and the possibility of human expeditions before about 2020 led to the publication of several popular Mars maps in the late 1990s. These may be said to include maps of the Cydonia region of Mars illustrating unconventional concepts regarding the artificiality of features such as the famous ‘ face, ’ showing place names, alignments, and architectural or geological interpretations.

4.3 Telescopic Mapping In The Space Age

New instruments and techniques have enabled mapping of many worlds not visited by spacecraft, including Pluto and the asteroid 4 Vesta. Radar images of Earth-approaching asteroids have been used to derive shape models and maps, and comet nuclei have been mapped very tentatively by observing changing patterns of material ejected from their surfaces. These maps usually appear in scientific literature and are rarely seen by a nontechnical audience. Numerous stars should be included among the mapped celestial bodies, since methods have been devised for interpreting features in their spectra in ways that lead to simple maps of phenomena in their photospheres. Interferometers operating at visible wavelengths may eventually permit the mapping of surface features on planets orbiting nearby stars. Even in this solar system, the number of mapped worlds will exceed 100 not far into the twenty-first century.

5. Science Fiction Mapping

Some science fiction books and fan magazines contain maps reflecting both the stories themselves and contemporary knowledge of their settings. Like other popular maps they help shape public awareness of the planets. Post (1979) illustrates some examples, but the subject would repay greater attention. Here are considered only fictional maps of real worlds, Mars being the most prominent example. Fictional maps once showed canals and ruined cities, but now often identify lowlands which become seas on a future Mars made more earthlike by colonists. Notable among works illustrated in this way are the ‘ Barsoom ’ (Mars) novels of Edgar Rice Burroughs and magazines relating to his work, and the novels of Kim Stanley Robinson. A different class of planetary map has evolved to support role-playing games. These maps frequently include a mixture of fictional and real surface features, and have appeared in atlas and sheet map form as well as illustrations in game manuals.

6. Conclusion

Planetary cartography is a broad and rapidly evolving field with a long history. It has not yet been examined in its entirety. Maps record both the history of astronomy and space exploration and a much broader cultural response to those endeavours. A systematic effort to collect and describe this material is needed, including an attempt to preserve the increasing number of ephemeral maps on the Internet.

Bibliography:

1. Blunck J 1982 Mars and its Satellites, 2nd rev. edn. Exposition Press, Smithtown, NY
2. Greeley R, Batson R M 1990 Planetary Mapping. Cambridge University Press, Cambridge, UK
3. Harley J B, Woodward D 1987 The History of Cartography. University of Chicago Press, Chicago, Vol. 1
4. Kopal Z, Carder R W 1974 Mapping of the Moon. Reidel Publishing, Dordrecht, Holland
5. Post J B 1979 An Atlas of Fantasy, new rev. edn. Souvenir Press, London
6. Whitaker E A 1989 Selenography in the seventeenth century. In: Taton R, Wilson C (eds.) The General History of Astronomy. Cambridge University Press, Cambridge, UK, Vol. 2