|German geologists inspecting the Hoba meteorite in 1929. Image courtesy of Marmet-Meteorites.com.|
One morning in 1920, Mr Jacobus Hermanus Brits, a farmer from Grootfontein in northern Namibia, was ploughing in his Hoba West Farm land with an ox when the plough came to a sudden screeching halt as it jammed up against something just below the surface. He began digging thinking he would find a large rock to pull out, and while he did find a rock, large turned out to be an understatement.
As Mr Brits kept removing soil covering the rock he soon realised this was no ordinary stone. To begin with it gave off a metallic sound when he hit it with his spade, and then there was the size; after much digging around it he finally uncovered the top, a square shape measuring almost 3 meters on each side.
When it was finally fully excavated it was found to be a solid piece of metal measuring 2.85 x 2.95 meters, with a thickness ranging from 0.75 to 1.2 meters.
Its enormous weight, estimated in 1920 to be 66 tons, made it impossible to move, so it was left where it was found and became a local attraction. It also made it the largest single-piece meteorite to be found on planet Earth, and the largest mass of natural iron on the Earth’s surface. Mr Brits is credited in some sources as being the first scientist to study the meteorite, but a plaque at the site clearly states Mr Brits was the discoverer of the meteorite.
Over the following decades the weight of the meteorite decreased due to human erosion when people took samples as souvenirs (and scientists as samples!). In an attempt to stop this the Namibian government declared the Hoba meteorite a National Monument on March 15, 1955, with permission from the then farm owner Mrs O. Scheel. In 1987, the farm owner Mr J. Engelbrecht donated the meteorite and surrounding land to the Namibian government, who built a visitor center and improved access to the meteorite itself by building a series of steps surrounding it.
The first surprising feature about the Hoba meteorite is its tabloid shape, with both major surfaces being flat; a very unusual feature for an object that has traversed the atmosphere from outer space. The other surprising feature is the lack of an impact crater, which has been linked in part to its shape.
It is conjectured that the object entered the atmosphere at a low trajectory, hitting the ground at terminal velocity and at a glancing angle such that it skipped over land, like a stone skipping on water, before coming to rest at its present location. It is estimated that this happened 80,000 years ago, while the meteorite itself formed some 190 – 410 million years ago.
The composition of the meteorite is 82.4% Iron, 16.4% Nickel, 0.76% Cobalt, 0.04% Phosphorus, with trace amounts of Copper, Zinc, Carbon, Sulphur, Chromium, Gallium, Germanium and Iridium. It is scientifically classified as nickel-rich ataxite. It also contains traces of minerals rarely found on Earth, such as Troilite, Schreibersite and Daubreelite.