Hoba is made almost exclusively of iron and weighs 60 tons. It came from Space, but left almost no crater.
In 1920, a farmer plowing a field in Grootfontein, Namibia, encountered an unexpected obstacle beneath the surface. When digging, he found a huge metal plate buried under a shallow layer of soil.
The find would prove to be absolutely extraordinary: weighing around 60 tons, it was the largest meteorite ever found to the surface of the Earth.
baptized by Because in reference to the Hoba West farm where it was discovered, the object is composed of approximately 84% iron and 16% nickel. But it wasn’t exactly the size that impressed scientists. What made the case particularly enigmatic was the unusually flat shape (almost square, about 2.7 meters long and wide and 0.9 meters thick) and, above all, the almost complete absence of an impact crater. Even much smaller meteorites tend to leave very obvious marks on the ground.
The investigators admitted two initial hypothesesrecalls: either the meteorite would have entered the atmosphere in an extremely unusual way, or it would have been moved by human intervention, the latter being considered a more unlikely scenario due to its weight.
In an article in 2013, the authors also discuss the possibility that Hoba had coming from a mother body that it did not fragment, or that it was just the first fragment found in a wider field of dispersal. But no other fragments are known, which weakens this third hypothesis.
The team also points out that there are no preserved signs of impact or historical records of the event. Studies with radionuclides (namely 59Ni) suggest that the meteorite may have been on Earth for less than 80 thousand years, enough time for any surface marks to have degraded and for there to be no written or ethnohistorical accounts of the fall.
Using physical models, researchers simulate scenarios capable of explaining how a block of this size could be practically “sitting” on the ground. The most plausible explanation is a entry into the atmosphere at low speed and at a very shallow angle, allowing atmospheric friction to remove much of the horizontal momentum. Already close to the ground, the meteorite would have lost most of its forward energy and hit the ground almost vertically, opening a relatively simple crater, however eroded.
According to these estimates, the impact could have created a depression about 20 meters in diameter and 5 meters deep. Today, Hoba remains in the place where it was found, practically intact, as one of the most intriguing metallic “testimonies” in the recent history of the Solar System.
