The meteorite fall in the Eastern Cape prompted a joint scientific investigation by researchers from the University of the Witwatersrand, Nelson Mandela University and Rhodes University. (Courtesy)
At 8.51am on August 25, residents in as far away as the Garden Route, Karoo, Western Cape and Free State witnessed a bright blue-white and orange streak of light moving across the sky.
The meteorite broke up into several smaller pieces and then disappeared from view, and shortly thereafter people reported hearing a loud explosion and feeling vibrations.
The meteorite fall in the Eastern Cape sparked a joint scientific investigation by researchers from the University of the Witwatersrand, Nelson Mandela University and Rhodes University.
They worked day and night to uncover various facts about the meteorite, including its origins, size, orbit, the speed it went through the atmosphere, and where it may have landed.
The findings of the meteorite were announced at a press conference at Nelson Mandela University on Tuesday. The rare meteorite fragment that was recovered has been tentatively named the “Nkweba meteorite”, after the town near where it was found.
The event was consistent with a rocky asteroid the size of a car entering Earth's atmosphere at extreme speed, said Roger Gibson, from the Wits School of Geosciences, with friction with the atmosphere creating a “spectacular fireball” that broke up in flight.
Among the witness accounts, researchers quoted 9-year-old Élésée Dutoit as she was sitting on the porch of her grandparents' house in Nkuba when she saw a black rock fall from the sky and land near a wild fig tree in the garden. The rock – black and shiny on the outside and light grey and concrete-like on the inside – was still warm when she picked it up and showed it to her mother.
Deon van Niekerk of Rhodes University received permission from the Eastern Cape Department of Cultural Heritage and Resources to retrieve all the fragments of the meteorite for scientific analysis.
Carla Dodd, a postdoctoral researcher in Nelson Mandela University's School of Geological Sciences, recognised the rarity and importance of such a find and quickly secured the samples Elise had collected.
“Our response time will be critical in collecting valuable scientific data, debris from the meteorite and explaining to local residents that this is a natural event and how the individual pieces are connected,” Gibson said.
Leonidas Vonopartis, from Wits School of Geosciences, said such events were “incredibly exciting” for both the public who witnessed the fall and the scientists who gained valuable information from studying the fireballs and rocks.
A bolide is a special type of firewall that explodes in a flash on the right side of the terminal, often with fragmentation.
“There are still many questions about the classification and origin of these rocks to be answered through systematic science,” he said.
“This event has happened relatively recently, and we as scientists are not very reactive creatures,” Dodd said. “We like to move slowly, and geologists in particular study rocks that have been around for millions of years, so we're not in much of a rush.”
“I think it's really significant that less than 12 hours after the fireball was seen and the impact noise was heard, there were indications that debris was being collected and the outlines of a plan were being prepared.”
The Nqweba meteorite is thought to be an achondrite meteorite, a rare species of the howardite-eucrite-diogenite group. It weighs less than 90 g and has an unfragmented diameter of about 5 cm.
The specimen has a dark black glassy coating (fused shell) and a light gray interior interspersed with dark and light green grains and rock fragments.
Gibson said there are 75,000 meteorites collected around the world — enough to fill two buses — and that fewer than a tenth of those are achondrites.
Over the next few weeks, a team of researchers and astronomers from the South African Astronomical Society will be collecting data from official observatories and eyewitness accounts to piece together a detailed account of the fireball event, as well as searching for further meteorite fragments.
The first scientific focus will be on the complete classification and origin of the fragments through microscopic and geochemical analysis, which will provide insight into the source regions of meteorites in space and potentially identify their parent bodies.
“We've received hundreds of reports from both aural witnesses and visual witnesses, and we're grateful for that,” Dodd added. “It's great to have multiple lines of evidence pointing to the same thing. This has really helped us pinpoint not only the flight path, but also scattered locations where other debris may have been.”