National Geographic looks at the rivalry between two early cartographers of Mars who based their maps on observations made during Mars’s “Great Opposition” in 1877: Nathaniel Green, whose Mars “was a delicately shaded world with landforms that gradually rose from vast plains and features that blended into one another” (pictured here) and Giovanni Schiaparelli, whose Mars had more detail—including those famous canals—but was less accurate.
The Closest Stars is the latest astronomical map produced as part of Kevin Jardine’s long-running Galaxy Map project: it shows stars within 10 parsecs (32.6 light years) of our solar system. (Earlier maps covered much more territory: this map goes out to 6,000 pc.)
It’s fascinating, and has a lot of interesting information, but there’s a problem. Like all maps, it reduces three dimensions to a flat plane; as such it distorts the distance of stars that are substantially above or below the galactic plane but not very far away on the x or y axis. Take Beta Comae Berenices: it’s 9.18 pc away and as such should be at the edge of the map, but because it’s 9.18 pc away on the z axis, at nearly a right angle to the plane, it appears on the map as one of the closest stars. The distance above or below the plane is marked in parentheses, but that’s not enough: a label can’t compensate for a misleading position on the map. On the smaller-scale maps this isn’t as much of an issue, because the galaxy is more or less a disk or a lens, but within a 10-pc radius? This isn’t the right projection for the job.
How do you depict elevation on a map of Mars? Earlier this year, Daniel Huffman posted a roundup of hypsometric tints for Mars.
I have a peculiar hobby of collecting Martian hypsometric tinting schemes: those sets of colors that cartographers use to depict elevations on the Red Planet. It’s a fascinating cartographic frontier. While the classic (and somewhat flawed) way of showing Earth’s elevations is to use a color scheme that starts with green lowlands, and then proceeds through some combination of brown/yellow/orange/red until it reaches white in the highest areas, there’s no standard yet for Mars. Maybe centuries from now, one of the schemes below will become that standard.
Huffman looks at fifteen schemes in total in the post, and in this video on YouTube:
Two geological maps of Venus have been published in Earth and Space Science. Produced by Vicki L. Hansen and Iván López, they each cover a 60-million-square-kilometre section of Earth’s twin: the Niobe Planitia Map Area geologic map (above, top) ranges from the equator to 57° north, and from 60° to 180° east longitude; the geologic map of the Aphrodite Map Area (above, bottom) is the Niobe Map Area’s southern hemisphere equivalent, covering the area from 60° to 180° east longitude, but from the equator to 57° south.
The March 2020 issue (PDF) of Calafia, the journal of the California Map Society, has as its theme the mapping of space. It also has something from me in it: my review of the third edition of Nick Kanas’s Star Maps: History, Artistry, and Cartography. An excerpt:
It’s important to remember a book’s target audience—its imagined ideal reader. In the case of Star Maps this is Kanas’s younger self, who came to map collecting via his lifelong interest in amateur astronomy. “I was frustrated that there was not a single book on celestial cartography that could inform me about the various aspects of my collecting,” he writes in the preface to the first edition. “What I needed was a book that not only was a primer for the collector but also had sufficient reference detail to allow me to identify and understand my maps. Nothing like this appeared, so I decided to write such a book some day” (p. xxi). In other words, for a compendium this is a surprisingly personal book, one that reflects his own journey into the subject and, presumably, his interests as a collector.
I’ll post the full review on The Map Room once I’ve checked my draft against the published copy. In the meantime, check out the issue of Calafia (PDF) in which it appears. (Update, 24 Jun 2020: Here it is.)
More on the question of whether GPS can be used for navigation on the lunar surface—that is to say the existing constellations of Earth-orbiting GNSS satellites, not a new constellation of satellites around the moon. A new study suggests that the answer is yes: GPS and other navigation systems could be used.
Cheung and Lee plotted the orbits of navigation satellites from the United States’s Global Positioning System and two of its counterparts, Europe’s Galileo and Russia’s GLONASS system—81 satellites in all. Most of them have directional antennas transmitting toward Earth’s surface, but their signals also radiate into space. Those signals, say the researchers, are strong enough to be read by spacecraft with fairly compact receivers near the moon. Cheung, Lee and their team calculated that a spacecraft in lunar orbit would be able to “see” between five and 13 satellites’ signals at any given time—enough to accurately determine its position in space to within 200 to 300 meters. In computer simulations, they were able to implement various methods for improving the accuracy substantially from there.
A mini-network of relays—a couple of satellites in lunar orbit, say—could improve accuracy further. [Geography Realm]
Previously: Many Moon Maps.
A new unified geologic map of the Moon, based on digital renovations that updated 1970s-era geologic maps to match more recent topographic and image data gathered by lunar orbiters, was released by the USGS last month. The map is “a seamless, globally consistent, 1:5,000,000-scale geologic map”; the paper version (25 MB JPEG) provides azimuthal projections beyond the 55th parallels and an equirectangular projection between the 57th parallels. [Geography Realm]
Previously: Lunar Geology and the Apollo Program.
Update, 22 April 2020: Version 2 of this map was released in March to address a number of errors in the first version.
The map legend colors represent the broad types of geologic units found on Titan: plains (broad, relatively flat regions), labyrinth (tectonically disrupted regions often containing fluvial channels), hummocky (hilly, with some mountains), dunes (mostly linear dunes, produced by winds in Titan’s atmosphere), craters (formed by impacts) and lakes (regions now or previously filled with liquid methane or ethane). Titan is the only planetary body in our solar system other than Earth known to have stable liquid on its surface—methane and ethane.
The map is the result of research published today in Nature Astronomy.
A team of researchers led by University of Hawaii astronomer Brent Tully has mapped the structure of the universe at a vast scale. In particular, they have mapped the shape of the Local Void, an empty expanse of intergalactic space hundreds of millions of light years across; the Milky Way is found at the edge of the Void. From the University of Hawaii’s Institute for Astronomy press release:
Now, Tully and his team have measured the motions of 18,000 galaxies in the Cosmicflows-3 compendium of galaxy distances, constructing a cosmographic map that highlights the boundary between the collection of matter and the absence of matter that defines the edge of the Local Void. They used the same technique in 2014 to identify the full extent of our home supercluster of over one hundred thousand galaxies, giving it the name Laniakea, meaning “immense heaven” in Hawaiian.
Mapping the Moon in Black and White, an exhibition curated by the Harvard Map Collection at Harvard’s Pusey Library, “guides you through the mutually reinforcing efforts to map the Moon using orbital imagery and the race to walk on the Moon. At ‘Mapping the Moon in Black and White,’ you will also learn how these mapping efforts sat within larger critiques of the Space Race, especially from Civil Rights organizations like the Southern Christian Leadership Conference and the Black Panther Party.” Runs until 31 October 2019; a reception and curatorial talk will take place on 18 September.
Planetary geologist David Rothery writes about the early attempts to map the Moon’s geology, both before and after the Apollo program. There was a symbiotic relationship between the map and the mission: maps suggested where landings might be most profitable from a geological perspective; and field work by the astronauts informed later moon maps.
The Atlas of Moons is National Geographic’s interactive guide to every single moon in the solar system (except for a few moons of dwarf planets and asteroids that we know next to nothing about). The big ones get interactive globes and additional description (as do Mars’s moons Phobos and Deimos, because we have imagery for them). Note that this is an extremely resource-intensive page that will use gigabytes of RAM if you let it.
With the 50th anniversary of Apollo 11 almost upon us, there’s been an uptick in moon-related content, which includes moon-related map content. For example:
New Exhibition. Opening today at The Map House in London, The Mapping of the Moon: 1669-1969, an exhibition of three centuries of lunar cartography. “The exhibition includes rare early 17th and 18th Century observations of the moon from astronomers such as Athanasius Kircher and Jean-Dominique Cassini, important maps produced by NASA for lunar exploration, globes and signed material by astronauts Neil Armstrong, Buzz Aldrin, Alan Bean and Jim Lovell.” Runs until 21 July. [ARTFIXDaily]
New Map. The July 2019 issue of National Geographic has a new map of the Moon that updates the 1969 painted version (see above) with a mosaic based on Lunar Reconnaissance Orbiter imagery. I don’t know whether that means a physical version of the map will be included with the issue as an insert, but I hope it does.
New Way to Navigate. NASA has a post on using GPS on the Moon. Now, I’d thought that using GPS on another world would require the deployment of a GPS satellite constellation around said world. No, this is about using Earth-orbiting GPS signals for lunar navigation, which simulations suggest is possible. The mind boggles.
Last week Eleanor Lutz, who gave us an old-style map of Mars in 2016 and a Goddesses of Venus map in 2017, announced her latest project: “Over the past year and a half I’ve been working on a collection of ten maps on planets, moons, and outer space. To name a few, I’ve made an animated map of the seasons on Earth, a map of Mars geology, and a map of everything in the solar system bigger than 10km.” In the coming weeks she’ll be going through each of those maps and explaining the design and source data for each. First up this week: her map of the solar system showing the orbits of every object larger than 10 km in diameter, from Mercury to the Kuiper Belt, and thousands of asteroids in between. [Universe Today]
Writing for Crosscut, Tom Reese memorializes his father, who worked as a cartographer and engineer for NASA’s Aeronautical Chart and Information Center during the Apollo program. Harlan Reese left behind a collection of maps, photos and charts in his garage which, Tom says, still contains “mesmerizing detail and mystery”:
One box has odds and ends of early lunar photography, some of the prints overlain with Dad’s hand-drawn compass points, landing site X’s and handwritten notations. The images were made through large telescopes on Earth, by the Surveyors and Rangers and Lunar Orbiters and early Apollos flying around and over the most promising landing sites. You can also see those smudged fingerprints that likely belong to Dad, mixed with those of many others who used magnifiers and X-Acto knives to carefully slice apart select sections of crater fields. Some small globs of cracked glue remain where they dripped during the process of pasting together the cut pieces to form mosaics of the unexplored landscape.
Some small indentations probably show how the prints were positioned in viewing devices like the extremely precise optical comparator, which helped human eyes interpret the length of shadows inside craters for the first time. These results were coordinated with data about altitude and lunar daylight to provide the most precise terrain measurements possible. Careful airbrushing would smooth over and fill in terra incognita with educated guessing. Finally, this data would be transformed into the precisely printed maps and charts that would help lunar lander pilots to, among other things, second-guess in real time the navigation decisions made by computers of the late 1960s and early 1970s.
Below, a Target of Opprtunity Flight Chart for the Apollo 11 mission: