Hoba meoeorite

July Editorial      

 

Famous meteorites

      To finish our short series on the largest and most famous, we turn to famous meteorites. Of course one can say that all meteorites are famous - they are extraterrestrial bodies that have reached the Earth's surface. But there are some which are more famous than the others for a number of different reasons: size, composition, force of impact and so on. Meteorites can be subdivided into three main groups: iron meteorites which are composed of iron and nickel (approximately 7% of Nickel); stony meteorites which represent the most diverse class of meteorites, ranging from primordial matter that has remained more or less unchanged for the last 4.5 billion years to highly evolved rocks from other differentiated worlds, such as the Moon or the planet Mars. There are also in-between meteorites called: stony-iron meteorites. Although the composition of individual stones in the last group can vary considerably between specimens, these meteorites have one thing in common - they are made up of roughly 50% of different stony components and 50 % of iron-nickel.

      The Hoba meteorite (pictured here) is the largest meteorite ever found. It still lies where it was found in 1920 at Hoba Farm, near Grootfontein in Namibia. It is an iron meteorite weighing more than 60 tonnes. The interesting point about Hoba is that it left no crater. It is speculated that this large iron meteorite entered the Earth's atmosphere at a very shallow angle and was slowed down considerably by atmospheric drag, so that its speed and angle of impact prevented a violent collision with the earth's surface. The second largest meteorite (Anighito) weighs approximately 34 tonnes and was discovered by Admiral Peary in 1892 at Cape York in Greenland. The largest meteorite found in the United States is the 15 tonne Willamette meteorite found in Oregon. Willamette is now housed in the The American Museum of Natural History in New York

      The Sikhote-Alin meteorite fell in the Sikhote-Alin Mountains approximately 400 km form Vladivostock on the morning of February 12, 1947 with a huge impact. A fireball heading for the Earth was sighted by many observers in a radius of approximately three hundred kilometres from the point of impact. The meteorite hit the atmosphere at a speed of about 14 km per second. Fortunately, it started to break apart as it hit , but still most of the fragments fell together. At an altitude of about 5.6 km above Siberia, the largest mass broke up in a violent explosion, so the Sikhote-Alin meteorite landed with a bang, leaving a number of craters, the largest being about 26 m across and 6 m deep. Although the largest fragment recovered was only 1,745 kg (now exhibited in the museum in Moscow) the total mass of the Sikhote-Alin was estimated at between 70 and 90 tonnes.

      The Orgueil meteorite landed near Orgueil in southern France on May the 14th 1864. This meteorite was classified as carbonaceous chondrite and it is the largest of only seven meteorites on that type ever found. It contains the rare gas xenon-HL and diamond dust. For research purposes, the Orgueil meteorite was split up into several pieces which can now be seen in museums in Europe and the USA. In 1965 one of these fragments was found, allegedly kept in a sealed glass container ever since the discovery. What was remarkable about this stone was the seed found in it. This caused great excitement and was headline news until it was discovered that the seed was glued to the meteorite by a hoaxer and the glue camouflaged with coal dust. The perpetrator of this hoax was never found.

      The biggest meteorite to land in Britain in recorded history was also a carbonaceous chondrite. It fell in pieces on the Leicestershire village of Barwell on Christmas Eve 1965. Some fragments penetrated deep into the driveway of one resident's home. Other bits damaged a car, and crashed through a factory roof. Although this meteorite could hardly be called famous, there was one fact which preserved its memory for posterity. The British Museum offered to buy all fragments found for seven shillings and sixpence per ounce (a useful sum of money in those days). Suddenly the quiet village of Barwell was swamped with 'treasure' hunters. Enough fragments were found to put the meteorite together, and it was found that, appropriately enough, that the Barwell meteoritewas about the size of a Christmas turkey.


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