In 1996, an archaeologist named Aly A. Barakat was doing fieldwork in an Egyptian desert and came across an unusual shiny black pebble now known as the Hypatia Stone (after Hypatia of Alexandria). Studies in recent years indicate that the stone is of extraterrestrial origin. And according to a recent paper published in the journal Icarus, the Stone’s parent body likely originated from a rare Type Ia supernova explosion.
The Hypatia stone was found in an area of southwestern Egypt known for its Libyan desert glass, produced by an extreme surface heating event, most likely a meteorite. The Hypatia stone may also have come from this impact, although more recent evidence suggests a comet as a more likely parent body.
Jan Kramers of the University of Johannesburg and several colleagues have studied the Hypatia Stone for many years. Kramers likened the internal structure of the Hypatia Stone to a fruitcake: poorly mixed batter forming the bulk of the pebble (mixed matrices), the mineral grains hidden within the inclusions of the stone representing cherries and nuts. He compared the secondary substances in the cracks of the stone to the flour dusting the holes in a fruitcake.
In 2013, Kramers and his colleagues published the results of a chemical analysis which provided strong evidence for the stone being a comet fragment. This analysis was a striking suggestion since most comet fragments found on Earth are microscopic dust particles in the upper atmosphere or buried in Antarctic ice. The comet hypothesis would explain the presence of microscopic diamonds in the stone, likely formed on impact when the comet exploded over Egypt around 28.5 million years ago. (The presence of these micro-diamonds is likely the reason the stone managed to make it to Earth without disintegrating)
However, work by other research teams in 2015 ruled out a comet or meteorite as the source of the stone, based on noble gas analyzes and nuclear probes. The mineral matrix simply does not resemble the composition of known meteorites: for example, it contains a massive amount of carbon and a small amount of silicon. So if it’s not coming from Earth, and it’s not typical of a comet or a meteorite fragment, where is it coming from?
Kramers et al. The 2018 micro-mineral analysis revealed that the matrix also contains a high concentration of polyaromatic hydrocarbons (PAHs) – a major component of interstellar dust – and these microscopic diamonds. The grains included aluminum, silver iodine, silicon phosphide and carbide, and a compound of nickel and phosphorus, with very little iron. The latter are elements that generally form the bulk of rocky planets. Based on this, Kramers and his colleagues suggested that the Hypatia stone contains matter that existed in space before our solar system was formed.