Name: Hoba “This is an OFFICIAL meteorite name” Abbreviation: There is no official abbreviation for this meteorite. Observed fall: No Year found: 1920 Country: Namibia
Mass: 60 tons
The Hoba or Hoba West meteorite lies on the farm “Hoba West”, not far from Grootfontein, in the Otjozondjupa Region of Namibia. It has been uncovered but, because of its large mass, has never been moved from where it fell. The main mass is estimated at more than 60 tons, making it the largest known meteorite (as a single piece) and the most massive naturally occurring piece of iron known on Earth’s surface.
Impact
The Hoba meteorite impact is thought to have occurred more recently than 80,000 years ago. It is inferred that the Earth’s atmosphere slowed the object to the point that it impacted the surface at terminal velocity, thereby remaining intact and causing little excavation.
Assuming a drag coefficient of about 1.3, the meteor would have been slowed to about 720 miles per hour (0.32 km/s) from its speed on entering the Earth’s atmosphere, typically in excess of 10 km/s for similar objects. The meteorite is unusual in that it is flat on both major surfaces, possibly causing it to have skipped across the top of the atmosphere like a flat stone skipping on water.
About 790,000 years ago, a meteor slammed into Earth with such force that the explosion blanketed about 10% of the planet with shiny black lumps of rocky debris. Known as tektites, these glassy blobs of melted terrestrial rock were strewn from Indochina to eastern Antarctica and from the Indian Ocean to the western Pacific. For more than a century, scientists searched for evidence of the impact that created these pitted blobs.
But the crater’s location eluded detection — until now.
Geochemical analysis and local gravity readings told researchers that the crater lay in southern Laos on the Bolaven Plateau; the ancient impact was concealed under a field of cooled volcanic lava spanning nearly 2,000 square miles (5,000 square kilometers), the scientists reported in a new study.
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Was the crater buried? On Laos’ Bolaven Plateau, the scientists found a site where fields of volcanic lava might have hidden signs of an older meteor impact. In a region that the researchers targeted as a likely spot for a crater, most of the lava flows were also in the right age range: between 51,000 and 780,000 years old.
In this geological map of the volcanic field’s summit region, the dashed, yellow ellipse marks the buried crater perimeter for the best-fitting gravity model. The dashed, white circle marks the buried perimeter that best fits geological observations. (Image credit: Sieh et al./PNAS 2019)
The study authors peered below the lava’s surface by taking gravity readings at more than 400 locations. Their resulting gravity map showed one area “of particular interest” with a gravitational anomaly, a subsurface zone less dense than the volcanic rock surrounding it. Their measurements hinted at an elliptical, “elongated crater” about 300 feet (100 m) thick, about 8 miles (13 km) wide and 11 miles (17 km) long, according to the study.
Together, all of these clues suggested that “this thick pile of volcanic rocks does indeed bury the site of the impact,” the scientists wrote.
