The International Astronomical Union (IAU) has approved new names for features on Mercury and agreed on a new theme for fossae on the planet. These newly christened features were discovered from images taken by the MESSENGER spacecraft during its first flyby of Mercury in January.

The IAU is the internationally recognized authority for assigning designations to surface features on celestial bodies. "We are very pleased with how quickly the IAU has responded to the need to name many of the prominent landforms on Mercury first seen in MESSENGER images," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "The Science Team has just submitted our first scientific papers on the flyby observations, and this prompt action by the IAU has meant that we are able to refer to these features by their formal names."

Naming rules exist for most features on planets, moons, and asteroids. Mercury's cliffs are named after the ships of famous explorers. One set of cliffs discovered by MESSENGER (called by the Latin name for cliffs, rupes) is named Beagle Rupes, after the ship on which naturalist Charles Darwin sailed around the world.

Craters on Mercury are named after famous deceased artists, musicians, or authors. The approved crater names are:

• Apollodorus, after Apollodorus of Damascus, a second-century Greek architect credited by many with designing the Pantheon temple in Rome.
• Atget, after Eugene Atget, a French photographer noted for his photographs documenting the architecture and street scenes of Paris.
• Cunningham, after Imogen Cunningham, an American photographer known for her portraits, still lifes, and figure studies.
• Eminescu, after Romanian poet Mihail Eminescu, considered to be the "godfather" of the modern Romanian language.
• Kertesz, after Andre Kertesz, a Hungarian-born American photographer famous for developing the photo essay.
• Neruda, after Chilean poet, Nobel laureate, and politician Pablo Neruda, most famous for his love poems.
• Raditladi, after Leetile Disang Raditladi, a Botswanan poet and playwright who founded the first political party in Botswana, the Federal Party.
• Sander, after German photographer August Sander best known for his portrait series.
• Sveinsdottir, after Juliana Sveinsdottir, one of Iceland's first woman painters and textile artists and a significant innovator from the 1930s to the 1950s through her approach to the landscape subject and color palette.
• Xiao Zhao, after Xiao Zhao, a Chinese artist from the Southern Song Dynasty (1127-1279) who once served as Emperor Gao Zong's dai zhao (painter-in-attendance) with the honorary title di gong lang (gentleman for meritorious achievement).

MESSENGER discovered a striking set of graben (or fault-bounded troughs) that radiate out from a small area near the center of the Caloris basin. An individual graben is termed a fossa (plural is fossae) by the IAU. No previous fossae had been discovered on Mercury from the Mariner 10 images, so the IAU had to approve a new naming scheme--"significant works of architecture." Pantheon Fossae were named after the Pantheon, a still-used second-century Roman temple and later church. The ancient building and the fossae both feature a central circular feature and radiating texture.

Arizona State University's Mark Robinson, who leads the development of global image products from MESSENGER, says he drew on a database maintained by the IAU, as well as requests from individuals, for nomenclature ideas.

"There's a certain romance to these names," says Robinson. "But more practically, naming these features facilitates communication among scientists studying the planet. It's very cumbersome to write a scientific paper and say, 'that big crater just east of that really huge crater near Mercury's North pole.' It's much easier to name the features."

An image of Mercury showing the locations of the newly named features is available online at http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=181.

During its first Mercury pass, MESSENGER's cameras imaged a large portion of Mercury's surface that had not been previously seen by spacecraft. (When Mariner 10, the only other space mission to visit Mercury, examined the surface 33 years ago, the Sun illuminated a different portion of the planet.) As the MESSENGER Science Team continues to study the images of Mercury, more features on Mercury will be named.

"The naming process is an ongoing effort because as we get more and more science out of the data we start finding more and more features," Robinson says.

MESSENGER will next fly past Mercury in October, viewing the opposite side of the planet. A third flyby is scheduled for September 2009, and the probe will settle into Mercury's orbit in March 2011.