Down to Earth With: The Geographers of the Solar System

by Harvey Leifert
Tuesday, January 13, 2015

Certain government officials have super cool titles: for example, Planetary Protection Officer (NASA’s Catharine Conley) and Oceanographer of the Navy (David Titley). I think Geographer of the Solar System would be right up there. Alas, no one actually has that title, but in a little-known office of the U.S. Geological Survey (USGS) nestled in the hills above Flagstaff, Ariz., I met a dozen or so people who could reasonably qualify for it.

The USGS Astrogeology Science Center, “Astro” for short, where about 90 scientists, engineers and technicians work, enjoys an illustrious history, but several long-time staffers lamented that its existence is virtually unknown to the general public and even to many geologists. I found that surprising, given the broad scope of Astro’s mission: to map extraterrestrial bodies, plan planetary exploration, and develop new technologies in data processing, archiving and distribution. To learn more, I paid a visit to the geologists of Astro last fall.

Entering Astro’s home, the Shoemaker building, I faced a display case dedicated to the career of Eugene Shoemaker. I was sensing a trend. Indeed, the spirit of Gene Shoemaker suffuses the organization that he created in 1961 to provide support and training for Apollo astronauts. He is also credited with coining the term “astrogeology.” Shoemaker’s widow and colleague Carolyn still maintains an office at Astro.

I called first on David Portree, who, as archivist, describes himself as “custodian of Astro’s memory.” He maintains a collection of more than 60,000 maps of planets and their moons. The archive is also home to Shoemaker’s chair (in which I was invited to sit) and his work table, both still in daily use.

Portree pulls out a hand-drawn map of the moon’s Copernicus Crater, signed “E. M. Shoemaker February 1960,” along with a modern full-color computer-generated map of the same area. He says that NASA’s decisions about where the Apollo missions should land on the moon were informed by geologic maps created at Astro, and Astro’s geologists took part in the discussions. Comparing the 1960 map with the modern computer-generated one illustrates how far lunar and planetary mapping has come in the past half-century.

Another example of how far we’ve come, Portree says, is maps of Mars. The Mariner missions to Mars in the 1960s and early 1970s provided data for the first detailed geological maps of that planet. Those missions, organized and headed by Astro scientists, “became the prototype for all subsequent long-term types of planetary missions,” he notes.

Just down the corridor from Portree’s archive is planetary geologist Kenneth Tanaka — in my view, a serious candidate for the title of Geographer of Mars. A 30-year-plus staffer at Astro, he is known for his highly detailed Martian maps, along with maps of the moon, Venus, and Jupiter’s major satellites.

“One of my current projects is to do a new global geologic map of Mars” at much higher resolution than any previous Mars map, combining data from all of the post-Viking missions, Tanaka says. The new map will address the geology of the Martian plains, including the geologic history of resurfacing and modification. “The geology is actually complex,” he says, “and there is some controversy on how these lowlands formed early in Martian history — whether there was a huge impact or whether there was a tectonic process.”

One of Tanaka’s more recent tasks was helping to select suitable landing sites for the Mars Science Laboratory (MSL), NASA’s latest Mars mission, which launched last November and is due to arrive at Mars in August. The sites that Tanaka, along with colleagues at Astro and elsewhere, identified were based on the mission’s objective of determining whether the environment at the landing site was ever suitable for the development of microbial life. NASA eventually chose one of the options, Gale Crater, as home base for its new, next-generation rover, Curiosity.

Tanaka also displays a 1983 map of Mercury, produced with data from the Mariner 10 mission. It looked rather detailed to me, but Tanaka says that data from the MESSENGER spacecraft currently orbiting the innermost planet will lead to significant updating of that map. “We’ll have higher quality and new sorts of data to map with,” he says.

Jennifer Blue is the only Astro staff member who actually carries the title of Geographer. Although she balks at expanding that to Geographer of the Solar System, she, perhaps more than anyone else, could lay claim to that title. Blue is the keeper of the “Gazetteer of Planetary Nomenclature.” The “Gazetteer” is the only official compilation of names of planets, their satellites and their major surface features. Blue emphasizes that she personally does not name anything; that is the sole responsibility of the International Astronomical Union (IAU), through its working groups.

Blue hands me a 1932 two-volume publication, “Named Lunar Formations,” IAU’s first attempt at regularizing lunar nomenclature. It comprises a catalogue volume and a map volume, covering more than 6,100 named features, and it took 20 years to produce. She also has a copy of the 1986 printed Gazetteer, published by USGS and optimistically labeled “Annual.” Actually, she says, the next edition appeared only in 1994, as the system became overwhelmed by the quantity of newly approved names. Two years later, the Gazetteer went online only, where it is continually updated. The site is easily accessible at

“Can I name a star after my girlfriend?” is the most frequent question Blue fields from the public. “We don’t even deal with stars, and most stars are given numbers, not names,” she says. She refers inquirers to an IAU website about buying star names from commercial enterprises and cautioning that such names have no official validity. Scientists also inquire sometimes, she says, mainly about naming craters or other planetary features for departed colleagues. IAU guidelines discourage commemoration as such, with rare exceptions, she tells them, also referring them to IAU for details.

Next, Lisa Gaddis welcomes me to her office, which is brightened by a wall display of men’s neckties in bold patterns. The designs come from thin sections of lunar rocks, viewed under polarized light, she says, adding, in the interest of full disclosure, that although the patterns are genuine, the striking colors were “tweaked” by the manufacturer. The ties are a clue that Gaddis’s research focuses on the moon’s geology.

“I’m involved primarily in the Lunar Reconnaissance Orbiter mission, with folks at ASU [Arizona State University] who run the Lunar Reconnaissance Orbiter Camera, the LROC system,” comprising both wide- and narrow-angle cameras, Gaddis says. She is also using data from Japan’s SELENE (Selenological and Engineering Explorer), also known as Kaguya.

From the data received from these instruments, Gaddis is mapping lunar volcanoes to a resolution of half a meter per pixel, “which is far better than we’ve ever seen,” she says. “We can see [meter-]sized boulders, and so we can see the distribution of materials around the vents, and this tells us something about the temperature of the lava that erupted there, the type of eruption.” She says she is currently interested in explosive eruptions, “which are gaseous, and they tend to be driven by volatiles, like carbon dioxide.”

Gaddis showed me a fist-sized rock of Arizona dunite, a relatively rare mineral composed mainly of olivine, formed under high temperature and pressure and brought to Earth’s surface by volcanic lava flows. “We think there may be similar kinds of deposits on the moon,” she says, “so that’s the kind of thing I’m looking for.”

The latest issue of interest to Gaddis is water. Based on recent data, it looks like “the moon is not as dry as we thought it was,” Gaddis says. When she was in school, she says, the common thinking was that the moon was extremely dry and always had been. Although there was never abundant, flowing water on the moon, recent research reveals that there is a small, but widespread amount of water. The lunar samples returned by Apollo astronauts also contain more water than had previously been realized, she says.

Gaddis also manages an archive of more than 300 terabytes of data on behalf of NASA’s Planetary Data System. The data comprise images of planets and other objects in the solar system, and Gaddis expects that the archive will soon reach 500 terabytes. (One terabyte equals 1 trillion bytes.)

Today, the scientists of Astro are both keepers of past information and participants in some of the most exciting new planetary and astrogeology research. It all started with Gene Shoemaker and the creation of Astro. Some of the first work at Astro had Shoemaker taking astronauts — including astronaut-geologist Harrison Schmitt, who also worked at Astro — to Meteor Crater, about an hour east of Flagstaff. There, they studied an impact crater and developed basic skills for geological research on the moon. At Meteor Crater’s visitor center, display cases and videos document Shoemaker’s role in assuring that the Apollo landings were significant scientific events.

Although he desperately wished to become an astronaut himself, Shoemaker never made it to the moon. After his death in a 1997 automobile accident at the age of 69, some of his ashes were carried aboard the Lunar Prospector mission, which intentionally crashed onto the lunar surface in 1999. To date, Shoemaker is the only person whose remains rest on the moon.

Astro has not rested on its laurels since the close of the Apollo era. Indeed, much more planetary research and mapping is under way in the hills above Flagstaff than I have space to recount here. The geographers of the solar system are still hard at work.

© 2008-2021. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the expressed written permission of the American Geosciences Institute is expressly prohibited. Click here for all copyright requests.