Science & Technology

The Mysterious Hypatia Stone Doesn't Match the Ingredients of Our Solar System

It's rare to find a meteorite on Earth. It's even rarer to find what was the core of a comet. Rarer still? A rock that didn't even come from our solar system. New research says that's just what geologist Aly Barakat found in 1996 when he was searching for Libyan desert glass in southwest Egypt.

Stone as Old as Time

The rock has since named the Hypatia stone after the earliest known female mathematician and astronomer, but even before that, Bakarat knew the stone he found was special. The object was covered in the kinds of microscopic diamonds that are a telltale sign of an extraterrestrial impact. In 2013, analysis by researchers at the University of Johannesburg did his hunch one better: Not only was the Hypatia stone from beyond our world, but it was also likely the core of a comet — the first one we've ever found.

But by 2015, other researchers were scratching their heads. It wasn't a meteorite, sure, but it also didn't contain the ingredients of any known comet. So for a paper published Dec. 28, 2017, the original Johannesburg team took a second crack at analyzing the Hypatia stone using sophisticated electron microscopy techniques.

Fruitcake of Mystery

They found that the stone is made up of three main components. Professor Jan Kramers, the lead researcher on the paper, likened it to a fruitcake that had fallen into a pile of flour and cracked on impact. "We can think of the badly mixed dough of a fruit cake representing the bulk of the Hypatia pebble, what we called two mixed 'matrices' in geology terms. The glace cherries and nuts in the cake represent the mineral grains found in Hypatia 'inclusions'. And the flour dusting the cracks of the fallen cake represent the 'secondary materials' we found in the fractures in Hypatia, which are from Earth," he said in a press release.

Seeing as the "flour" is from our own planet, it's the "dough" and "fruit" that are of real interest. The dough, or mineral matrix, is all wrong for an object from our solar system. "If it were possible to grind up the entire planet Earth to dust in a huge mortar and pestle, we would get dust with on average a similar chemical composition as chondritic meteorites," said Kramers. What's more, the matrix also contains the kinds of carbon compounds you generally see in interstellar dust — not something you typically find in our neck of the woods.

But the Hypatia stone's real claim to fame is the "fruit," or mineral grains. They're made up of nickel, phosphorus, and iron, but not in any ratio we're familiar with. And that, say the researchers, could mean the stone formed before our sun did. "We think the nickel-phosphorus-iron grains formed pre-solar, because they are inside the matrix, and are unlikely to have been modified by shock such as collision with the Earth's atmosphere or surface, and also because their composition is so alien to our solar system," said Kramers.

If it didn't form before our solar system, however, that means something much stranger. The reigning theory is that the bodies in our solar system formed from a huge, uniform cloud of dust. That's why you find the same compounds in all of the rocky stuff: planets, moons, meteors. If the Hypatia stone formed around the same time as everything else, that means the cloud wasn't uniform.

Either way, we know that the Hypatia stone formed in the kind of cold environment you find way, way beyond Neptune. "We know very little about the chemical compositions of space objects out there," Kramers said. "So our next question will dig further into where Hypatia came from."

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For a beautiful dive into planetary geology, check out "In Search of Stardust: Amazing Micrometeorites and Their Terrestrial Imposters" by Jon Larsen. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Written by Ashley Hamer February 22, 2018

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