Pebble might be key to Earth’s origin

Hypatia, the first great female astronomer and mathematician, lived in Egypt in the 5th Century AD. 

Pebble might be key to Earth’s origin

Following a smear campaign by Cyril, Bishop of Alexandria, this tolerant pagan was lynched by Christian monks in 415. What Voltaire called ‘Cyril’s tonsured hounds’ dragged the 60-year old pacifist into a church, stripped her naked, and battered her to death.

Artists and writers have been inspired by Hypatia’s story and the 2009 film, Agora, chronicled her life. In it, she embraces Aristarchus’ theory that the sun, not the Earth, is the centre of the solar system. There is no historical evidence that she anticipated Copernicus, but a pebble discovered in her native Egypt may herald another astronomical revolution. A mysterious ‘Hypatia stone’ is challenging current theories of the Earth’s origin.

Meteorites burn up on entering the atmosphere, becoming ‘shooting stars’ or ‘meteors’. Their remnants reach the ground occasionally. These are easiest to spot in the desert. In 1996, geologist, Ali Barakat, found a mysterious, 30-gram one in the arid wastes of south-west Egypt. The multi-coloured pebble was unlike any other meteorite.

The area where the stone was found abounds in ‘Libyan Desert glass’, a shiny, greenish material resembling ‘trinitite’, created from sand in the New Mexican desert by the heat of the world’s first nuclear detonation. The ‘Trinity test’ took place in August, 1945. Desert glass is the product of a similar cataclysmic event: the fiery demise of a meteorite, several metres in diameter, entering the Earth’s atmosphere 26m years ago. The Hypatia stone is probably a fragment of that meteorite. A sample of it has been exhaustively analysed at the University of Johannesburg. The results, just released, are setting the cat among the astronomical pigeons.

There are three types of meteorite. Most are lumps of stone. ‘Iron’ meteorites consist of iron-nickel alloys, while ‘stony-iron’ ones contain both rock and metal. Many originate in the ‘asteroid belt’ between Mars and Jupiter, where debris and broken-up dwarf planets orbit the sun. Others may be remnants of comets emanating from the mysterious Kuiper Belt, beyond the orbit of Neptune or the more remote Oort Cloud, at the outer limit of the solar system. These ‘belts’ possibly date from the time when the planets we observe today were being formed, about 4.5bn years ago.

The tests in Johannesburg confirm that the Hypatia stone is of extra-terrestrial origin. The shock and immense heat of impact with the atmosphere created tiny diamonds, which preserved it from weathering through countless millennia. Thanks to them, we are able to understand events that took place billions of years ago. Meteorites normally contain lots of silicon and little carbon. Hypatia’s one, however, has huge amounts of carbon, but hardly any silicon. Also, the ratios found in its nickel-phosphorus-iron grains are completely different from terrestrial ones and from those of other meteorites.

According to our current theory, the planets formed from particles of interstellar dust, pulled together by gravity. It’s assumed that the dust had the same composition everywhere.

Some of the carbon compounds in the Hypatia fragment, however, are different from any found on Earth. Is the stone, therefore, older than the solar system or did it come from somewhere else?

“The little pebble, from the Libyan Desert, glass-strewn field in south-west Egypt, presents a tantalising piece of an extraterrestrial puzzle that is getting ever more complex,” says Jan Kramer, leader of the Johannesburg research team. Her stone would have fascinated Hypatia.

  • University of Johannesburg

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