As I said during the Q&A part of my fantasy maps presentation at Readercon (see previous entry), maps of other worlds in the solar system are usually images from space probes that have been set to a map projection. The key word is usually. On Monday the U.S. Geological Survey releaseda geologic map of Mars that “brings together observations and scientific findings from four orbiting spacecraft that have been acquiring data for more than 16 years.” Via io9 and Wired.
Maps of Paradise by Alessandro Scafi (University of Chicago Press, 11/13). Explores “the diverse ways in which scholars and mapmakers from the eighth to the twenty-first century rose to the challenge of identifying the location of paradise on a map, despite the certain knowledge that it was beyond human reach.” (Amazon)
The USGS has released quad maps of the planet Mercury as a set of PDF files: “The 1:5 million-scale series of Mercury maps divides Mercury into 15 quadrangles, H-1 through H-15 (five Mercator, eight Lambert Conformal, and two Polar Stereographic quadrangles). The base mosaic was produced with orbital images by the MESSENGER Team and released by NASA’s Planetary Data System on March 8, 2013. This new global mosaic includes 100% coverage of Mercury’s surface.”
We’re still two years from the New Horizons flyby of Pluto, but the cartography of the solar system’s most famous dwarf planet—based on Hubble imagery—is already several kinds of problematic, as Emily Lakdawalla explains in a post that also explains how the cartography of other worlds is done. (Key challenges include defining the north and south pole—which one is which?—as well as a prime meridian.)
Lorenz’s team used a mathematical process called splining—effectively using smooth, curved surfaces to “join” the areas between grids of existing data. “You can take a spot where there is no data, look how close it is to the nearest data, and use various approaches of averaging and estimating to calculate your best guess,” he said. “If you pick a point, and all the nearby points are high altitude, you’d need a special reason for thinking that point would be lower. We’re mathematically papering over the gaps in our coverage.”
NASA has released a free-airgravity map of the Moon: “If the Moon were a perfectly smooth sphere of uniform density, the gravity map would be a single, featureless color, indicating that the force of gravity at a given elevation was the same everywhere. But like other rocky bodies in the solar system, including Earth, the Moon has both a bumpy surface and a lumpy interior. … The free-air gravity map shows deviations from the mean, the gravity that a cueball Moon would have.” Gravity data comes from the GRAIL mission, with the digital elevation model provided by the Lunar Reconnaissance Orbiter laser altimeter. Image credit: NASA’s Goddard Goddard Space Flight Center Scientific Visualization Studio.
Paul Schenk’s Atlas of the Galilean Satellites (Cambridge University Press, 2010) collects all the imagery gathered by the Voyager and Galileo missions of the four major moons of Jupiter (Callisto, Ganymede, Europa and Io, all discovered by Galileo in 1610) and assembles them into global, quadrangle and area maps. But this heavy, 400-page tome begins with a confession. “This Atlas is not what it should be.” The failure of the high-gain antenna on the Galileo spacecraft meant that far less data could be transmitted back to Earth during its nearly eight-year mission than had been planned. Large tracts of the moons are mapped in low resolution; the fuzzy images yield little detail. But until another mission is sent—the Juno probe now en route to Jupiter will not be studying the moons—this is all there will be for the foreseeable future. For decades, in fact.
The Atlas of the Galilean Satellites therefore represents a treasure trove of all available imagery of these four moons. The further out you go, the less imagery there is: outermost Callisto gets 49 pages of plates, innermost Io, with all its interesting volcanoes, gets 89. Despite the inevitable blurry patches, there are some extraordinarily high-detail images here. One problem, though, is that the global maps are unlabelled; I found it difficult to place features that were labelled on the quadrangle, regional and detail maps in their global context. Also worth noting is that—and I suspect this is the norm for extraterrestrial mapping—these are not maps per se, but spacecraft imagery labelled and put on a map projection.
One issue that has been noted elsewhere—for example, in Emily Lakdawalla’s review last November—is that several copies of this book have been defective, with pages falling out. My own copy is fine, but seems a bit fragile. (UPDATE: Laying it open flat once was enough for several pages to come loose.) The signatures appear to be glued rather than sewn—a textbook example of the badly built British book—which is inexplicable given the size of the book and weight of the glossy paper, to say nothing of its cost. Because, at $165 (£95) list, this book is extremely expensive; ebook versions are just as exorbitant. Cheaper copies can be found elsewhere with a little digging: I got mine via AbeBooks for less than $30, shipping included. Honestly, given the risk of the book falling apart on you, that’s the way to go.
This atlas isn’t really aimed at beginners or people with a casual interest in the solar system. The price reflects that, as does its rather technical nature and organization. Those with a serious jones for the solar system will not be deterred by these or any other reservations.