Mercury
In Roman mythology, a god of commerce and gain, and messenger of the gods. He was identified with the Greek Hermes, and similarly represented with winged sandals and a winged staff entwined with snakes.
A temple near the Circus Maximus was dedicated to him, and his festival was celebrated on 25 May by the mercuriales, members of a college regulating the corn trade.
mercury
Heavy, silver-grey, metallic element, atomic number 80, relative atomic mass 200.59. Its symbol comes from the Latin hydrargyrum, derived from the Greek words for water and silver. It is a dense, mobile liquid with a low melting point (−38.87°C/−37.96°F). Its chief source is the mineral cinnabar, HgS, but it sometimes occurs in nature as a free metal.
Uses
Its alloys with other metals are called amalgams (a silver–mercury amalgam is used in dentistry for filling cavities in teeth). Industrial uses include drugs and chemicals, mercury-vapour lamps, arc rectifiers, power-control switches, barometers, and thermometers.Hazards
Mercury is a cumulative poison that can contaminate the food chain, and cause intestinal disturbance, kidney and brain damage, and birth defects in humans. Where liquid mercury is handled, vapours are also a health risk. The World Health Organization's ‘safe’ limit for mercury is 0.5 milligrams of mercury per kilogram of muscle tissue. The US Environmental Protection Agency recommended a maximum safe level for mercury of 0.1 mg per kilogram of body weight in January 1998 (a fifth of that recommended by WHO).The discharge into the sea by industry of organic mercury compounds such as dimethylmercury was the chief cause of mercury poisoning in the latter half of the 20th century.Between 1953 and 1975, 684 people in the Japanese fishing village of Minamata were poisoned (115 fatally) by organic mercury wastes that had been dumped into the bay and had accumulated in the bodies of fish and shellfish.
History
The element was known to the ancient Chinese and Hindus, and is found in Egyptian tombs of about 1500 BC. It was named by the alchemists after the fast-moving god, for its fluidity.Use in miningMercury forms an amalgam with gold and so is used in gold mining to extract gold from low-grade deposits. Each year 250–300 tonnes are used in the Amazon basin alone. In 1990 mercury concentrations in edible fish close to the mining sites were ten times greater than the WHO recommended limits for human consumption. |
Mercury
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Closest planet to the Sun. Its mass is 0.056 that of Earth. On its sunward side the surface temperature reaches over 400°C/752°F, but on the ‘night’ side it falls to −170°C/−274°F.
Mean distance from the Sun
58 million km/36 million miEquatorial diameter
4,880 km/3,030 miRotation period
59 Earth daysYear
88 Earth daysAtmosphere
Mercury's small mass and high daytime temperature mean that it is impossible for an atmosphere to be retained.Surface
composed of silicate rock often in the form of lava flows. In 1974 the US space probe Mariner 10 showed that Mercury's surface is cratered by meteorite impacts.Satellites
noneNASA's Mariner 10 probe, launched on 3 November 1973, arrived at Mercury on 29 March 1974, and provided the first close-up images of the planet. NASA launched a US$286 million mission to Mercury in 2004 to orbit the planet during 2008, 2009, and 2011. It will photograph the planet's surface, analyse its atmospheric composition, and map its magnetic field. The European Space Agency, in collaboration with Japan, plans to send probes to orbit Mercury, arriving in 2015 after a four-year journey.
| Mercury's largest known feature is the Caloris Basin, 1,400 km/870 mi wide. There are also cliffs hundreds of miles long and up to 4 km/2.5 mi high, thought to have been formed by the cooling of the planet billions of years ago. Inside is an iron core three-quarters of the planet's diameter, which produces a magnetic field 1% the strength of Earth's. |
Mercury
| Nickname of Joseph Haydn's symphony no. 43, in E flat major, composed c. 1771. |
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