This meteorite fall in the Eastern Cape sparked a collaborative scientific investigation that involved researchers from the University of the Witwatersrand, Nelson Mandela University and Rhodes University. (Supplied)
At 8.51am on 25 August, residents from as far afield as the Garden Route, the Karoo, the Western Cape and the Free State saw a bright blue-white and orange streak of light moving through the sky.
The meteorite, after splitting into several smaller fragments, disappeared from view. Shortly afterwards, people reported hearing loud explosions and sensing vibrations.
This meteorite fall in the Eastern Cape sparked a collaborative scientific investigation that involved researchers from the University of the Witwatersrand, Nelson Mandela University and Rhodes University.
They have worked around the clock to establish various facts about the meteorite, including its probable origin, size and trajectory, and speed as it entered Earth’s atmosphere as well as the possible fall area.
The results of their search for facts about the meteorite were announced at a media briefing at Nelson Mandela University on Tuesday. The rare meteorite fragment that has been recovered is provisionally named the “Nqweba Meteorite” after the nearby town of its discovery.
The incident is consistent with a rocky asteroid about the size of a car entering Earth’s atmosphere at very high speed, said Roger Gibson, of the Wits School of Geosciences. Friction with the atmosphere created a “spectacular fireball” and caused it to break up in flight.
Among the eyewitness accounts, the researchers credited nine-year-old Eli-zé du Toit, who was sitting on her grandparents’ porch in Nqweba when she saw a dark rock fall from the sky and land near a wild fig tree in the garden. The rock, black and shiny on the outside with a light grey, concrete-like interior, was still warm when she picked it up and showed it to her mother.
Deon van Niekerk, of Rhodes University, obtained a permit from the Eastern Cape Provincial Heritage Resources Authority to recover all fragments from this meteor for scientific analysis.
Carla Dodd, a postdoctoral research fellow in the department of geoscience at Nelson Mandela University, quickly secured the sample collected by Eli-zé, recognising the rarity and importance of such a find.
“Our response time was going to be critical if we were going to collect valuable scientific data and meteorite fragments, as well as to explain to the local public that this was a natural event and how the individual parts linked together,” Gibson noted.
Events such as these are “incredible and are very exciting”, both for the public who witness these falls and the scientists who gain invaluable information from studying the bolides and rocks, said Leonidas Vonopartis, of the Wits School of Geosciences.
A bolide is a special type of firewall that explodes in a right terminal flash, often with fragmentation.
“There are lots more questions about the classification and origin of this rock that will be followed up through methodical science,” he said.
“Not a lot of time has passed since this event has occurred and we scientists are not very reactive creatures,” Dodd said. “We like to move slowly and especially as geologists, we are not often in a rush since we study rocks that have been around for millions of years.
“I think it’s really significant that in less than 12 hours since the bolide was sighted and the sonic boom was heard, we already had an indication that meteorite fragments were collected and we had a semblance of the plan in place.”
The Nqweba Meteorite is believed to be an achondritic meteorite, a rare type in the Howardite-Eucrite-Diogenite group. It weighs less than 90g and has a pre-fragmentation diameter of about 5cm.
The specimens have a dark black glassy coating (fusion crust) with a light grey interior, peppered with dark-green and light-green grains and clasts.
Gibson said that globally, 75 000 meteorites have been collected that would fit into two passenger buses. Of these, less than one in 10 would be achondritic meteorites.
In the coming weeks, a team of researchers and astronomers affiliated with the Astronomical Society of Southern Africa will collect data from official observatories and eyewitness accounts to piece together the details of the bolide event. They will also search for more meteorite fragments.
The initial scientific focus will involve microscopic and geochemical analysis of the fragment to fully classify it and understand its origin. This investigation could provide insights into the meteorite’s source region in space and possibly identify its parent body.
“We have received hundreds of reports from both ear witnesses and eye witnesses and we thank you for that,” Dodd added. “It’s great to have these multiple lines of evidence pointing at the same thing. This has really helped us to define the flight path as well as the strewn field where there may be other fragments.”
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