By Lehlohonolo Lehana.
A team of scientists and researchers has confirmed that the bolide that fell into the Indian Ocean over St Francis Bay in the Eastern Cape a few weeks ago is indeed a meteorite.
On Sunday, 25 August, people on the Garden Route, the Sunshine Coast, in Nelson Mandela Bay and even as far as the Karoo heard a big bang. Many looked up to the sky and saw a bright flash streaking through the winter air. Some reached for their phones to take pictures, others to post that the aliens are coming.
The discovery sparked collaborative effort from scientists from three universities in the country, Wits University, Rhodes University and the Nelson Mandela University trying to piece together the timeline of the meteorite and the origin thereof.
According to Rhodes University Communications and Marketing Manager, Christelle du Toit, researchers from the University of the Witwatersrand, Nelson Mandela University, and Rhodes University have worked around the clock to establish various facts about the meteorite, including the probable origin, size and trajectory, and speed as it entered Earth’s atmosphere, as well as the possible fall area.
The bolide – a fireball streaking across the sky – has been given a preliminary classification as a rare type of rare meteorite called an achondrite based on fragments that were found in Kirkwood. Only one in 10 of some 75 000 meteorites that have been discovered on Earth turn out to be achondrites.
Dr Deon van Niekerk of Rhodes University obtained a permit from the Eastern Cape Provincial Heritage Resources Authority to recover all fragments from the meteor for scientific analysis.
“There are five fragments in total. The meteorite broke down when it hit the ground”, said van Niekerk of the electron microscopy unit at Rhodes University, in a presentation on Tuesday.
“If we compare images of these samples with other meteorites that have been found and classified, we can make a preliminary conclusion that these are fragments of a howardite eucrite diogenite (HED) meteorite.”
Prof Roger Gibson of the University of the Witwatersrand says: “Teams from the three universities corroborated eyewitness (and “earwitness”) accounts with video footage and data from a National Council of Geosciences ground station to plot the meteorite’s path and identify where other fragments may have fallen.
The team concluded that the meteorite, about 1-1.5m in size, entered Earth’s atmosphere around 8.50am SAST last Sunday morning over the coastline between Gqeberha and George. The object was travelling at 20km/s, or 72 000km/h. Penetration into denser atmosphere caused friction with air molecules and so the object began to glow and melt, losing a lot of its volume.
The object was travelling at supersonic speeds, which caused shockwaves (sonic booms), but the sound could only be heard long after the object had hit the ground. The explosion, which caused the object to split apart and which was caught on video, happened at an altitude of 38km.
Dr Carla Dodd, a microbial scientist from Nelson Mandela University, was the first scientist to handle the meteorite.
She relates how the story unfolded: “I was out cycling and when we heard the noise we first thought it might be thunder or an earth tremor.”
“For your everyday citizen it’s a cool thing to see and to witness. As much as it means a lot for the science world, it’s also a big deal for our social experience. People must understand that things like this don’t happen often. So, to be here and to bear witness to it, is really something special,” said Dr Dodd.
Collaborative effort
The investigation into the Meteorite involves a co-ordinated effort between scientists from Nelson Mandela, Rhodes and Wits universities.
In the coming weeks, a joint 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 event. They will do extensive searches for further meteorite fragments over a wide area of rugged terrain.
The team is still seeking permission from landowners over the space rock’s trajectory. Once obtained, ground teams will investigate and try to find other fragments.
What’s next?
The initial scientific focus will involve microscopic and geochemical analysis of the recovered meteorite fragment to fully classify it and understand its origin.
The investigation could provide insights into the meteorite’s source region in space and possibly identify its parent body.
Gibson thanked South Africans who used social media to provide eyewitness accounts. These helped the team figure out the meteorite’s path and corroborate theories about the object. He also warned of the danger these objects pose in general, even though this particular meteorite was in the end benign.