The International Astronomical Union (IAU) recently approved a proposal from the MESSENGER Science Team to assign names to 10 rupes, the long cliff-like escarpments that formed over major faults along which one large block of crust on Mercury was thrust up and over another.

The IAU has been the arbiter of planetary and satellite nomenclature since its inception in 1919. In keeping with the established naming theme for rupes on Mercury, all of the newly designated features are named after ships of discovery.

"We proposed the name Enterprise Rupes for the longest rupes on Mercury, which is 820 kilometers (510 miles) long. The USS Enterprise was launched in 1874 and conducted the first surveys of the Mississippi and Amazon rivers," says Michelle Selvans of the Center for Earth and Planetary Studies at the National Air and Space Museum. Selvans led the effort to name this group of rupes.

"We also recommended some fun names, such as Calypso Rupes, for Jacques Cousteau's ship," she says. And other names were proposed for their personal connections, such as Palmer Rupes, named after an icebreaker research vessel on which Selvans sailed to conduct marine geophysics research offshore of Antarctica. The other names are

* Alvin Rupes, after DSV Alvin. Built in 1964 as one of the world's first deep-ocean submersibles, Alvin has made more than 4,400 dives. It can reach nearly 63 percent of the global ocean floor.

* Belgica Rupes, after RV Belgica. Built in 1884, this steamship was originally designed as a whaling ship. It was converted to a research ship in 1896 and took part in the Belgian Antarctic Expedition of 1897-1901, becoming the first ship to overwinter in the Antarctic.

* Carnegie Rupes, after a yacht launched in 1909 as a research vessel. The ship was built almost entirely from wood and other non-magnetic materials to allow sensitive magnetic measurements to be taken for the Carnegie Institution's Department of Terrestrial Magnetism. During 20 years at sea the vessel traveled nearly 500,000 kilometers (300,000 miles) and carried out a series of cruises until an onboard explosion in port destroyed the ship in 1929.

* Duyfken Rupes, after a small Dutch ship built in the late 16th century. In 1606, the vessel sailed from the Indonesian island of Banda in search of gold and trade opportunities on the island of Nova Guinea. Under the command of Willem Janszoon, the ship and her crew did not find gold, but they did discover the northern coast of a huge continent: Australia.

* Eltanin Rupes, after the USNS Eltanin, launched in 1957 as a noncommissioned Navy cargo ship. The vessel was built with a double hull and officially classified as an Ice-Breaking Cargo Ship. In 1962, the ship was refitted to perform research in the southern oceans and reclassified an Oceanographic Research Vessel. Magnetic field measurements made with the Eltanin were critical in validating the hypothesis of sea-floor spreading.

* Nautilus Rupes, after the Exploration Vessel Nautilus. In service since 1967, the ship has conducted underwater studies in archeology in the Mediterranean and Caribbean seas. The vessel is currently equipped with remotely operated vehicles and a high-bandwidth satellite communication system for remote science and education.

* Terror Rupes, after the HMS Terror. Built in the early 1800s as a British Royal Navy bomb vessel, the ship was involved in the bombardment of Fort McHenry, one of the last battles of the War of 1812. The bombardment provided the inspiration for Francis Scott Key to write the American national anthem "Star Spangled Banner." After being retrofitted for polar exploration, the ship participated in Antarctic exploration.

Selvans says that Mercury's rupes are revealing a great deal about the evolution of the planet. Each feature formed over a major fault system that accommodated kilometers of horizontal shortening of Mercury's crust. The accumulated contraction taken up by the faults that underlie the rupes collectively records the cooling and contraction of Mercury's interior over the past 4 billion years of planetary history.

In choosing those rupes to receive names, the team picked from among the longest and most geologically interesting features that have been imaged by MESSENGER. "These features are easy to identify in images taken at dawn and dusk, when they throw shadows along their entire length," Selvans says. "A crisp shadow that is only about 1 kilometer wide but hundreds of kilometers long really stands out in images."

Since 1976, the IAU has approved names for 27 rupes on Mercury. The latest names are the first new designations for rupes in more than five years.

"The MESSENGER team is grateful to the IAU for their approval of formal names for rupes on Mercury," adds MESSENGER Principal Investigator Sean Solomon of Columbia University's Lamont-Doherty Earth Observatory.

"MESSENGER observations have revealed that these deformational features accommodated far more crustal contraction than indicated by earlier estimates. The new names will permit the MESSENGER team to document this finding in a clear and straightforward manner. Moreover, the names give us the opportunity to recognize that the exploration of Earth's oceanic regions continues in parallel with the exploration of Earth's sister planets."

More information about the names of features on Mercury and the other objects in the Solar System can be found at the U.S. Geological Survey's Planetary Nomenclature Web site.