Two University of Johannesburg researchers are questioning the origin of a stone found in Egypt.
Professor Jan Kramers and Dr Georgy Belyanin, from UJ's Paleoproterozoic Mineralization (PPM) Research Centre, announced in 2013 that the "Hypatia" pebble found in south-west Egypt was not from earth.
The stone was named after Hypatia of Alexandria, who was also one of the first women to study math, astronomy and philosophy.
The researchers found exotic micro-mineral compounds in the stone that are not known to occur on earth, or elsewhere in the solar system, meteorites or comets.
Two years later, other research teams announced that the stone was not part of any known types of meteorite or comet, based on noble gas and nuclear probe analyses.
Formed in cold temperatures
"What we do know is that Hypatia was formed in a cold environment, probably at temperatures below that of liquid nitrogen on earth (-196°C)," Kramers said.
Kramers, who was recently recognised as a "leading international researcher" by the National Research Foundation, said the research now needed to determine what the stone's origins were and if the minerals could provide clues on where it came from.
"In our solar system it would have been way further out than the asteroid belt between Mars and Jupiter, where most meteorites come from," he said.
"Comets come mainly from the Kuiper Belt, beyond the orbit of Neptune and about 40 times as far away from the sun as we are," he said.
"Some come from the Oort Cloud, even further out. We know very little about the chemical compositions of space objects out there. So, our next question will dig further into where Hypatia came from," Kramers said.
The researchers said the discovery of Hypatia presented a "tantalising piece for an extraterrestrial puzzle that is getting ever more complex".