MESSENGER Team Names Ten Major Fault Scarps On Mercury

April Flowers for redOrbit.com — Your Universe Online

Recently, the MESSENGER Science Team proposed names for 10 rupes on Mercury. The International Astronomical Union (IAU), which has been the arbiter of planetary and satellite nomenclature since 1919, approved the names. In keeping with the theme of naming rupes on Mercury, they all bear the names of ships of discovery.

Rupes is the Latin word for cliff, which perfectly suits the formations on Mercury. They are long cliff-like escarpments that form over major faults. One large block of crust thrusts up and over another along these fault lines. Currently, “rupes” is only used by planetary geologists to describe formations on other worlds than Earth.

“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. Some names were chosen for their personal connection to the team, such as Palmer Rupes — named after an icebreaker research vessel Selvans sailed on to conduct marine geophysics research off the coast of Antarctica.

The other names accepted 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 and can reach nearly 63 percent of the global ocean floor.
• Belgica Rupes, after RV Belgica. Originally designed as a whaling ship in 1884, the steamship 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. 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, the ship spent 20 years at sea. The vessel traveled nearly 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. The ship and her crew did not find gold, instead they found something more scientifically exciting: the northern coast of Australia.
• Eltanin Rupes, after the USNS Eltanin, launched in 1957 as a noncommissioned Navy cargo ship. The ship had a double hull and was 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 Nautilus has conducted underwater studies in archeology in the Mediterranean and Caribbean seas. The vessel is currently equipped with remotely operated vehicles (ROVs) 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.” The ship was retrofitted for polar exploration and has participated in Antarctic exploration.

According to Selvans, Mercury´s rupes are revealing a great deal about the planet´s evolution. Each of the rupes formed over a major fault system that, in turn, accommodated kilometers of horizontal shortening of the planet´s crust. The accumulated contraction represented by this shortening collectively records the cooling and contraction of Mercury´s interior over the last four billion years.

To decide which rupes to name, the team chose the longest and most geologically interesting features 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, 27 rupes have been named on Mercury. The ten new 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.”