A new analysis of a small rock called the Hypatia Stone, presumed to be a fragment from a comet, reveals that it might either be from outside the Solar System, or older than the Sun itself.

Discovered in 1996 in the same region of the Eastern Sahara as the odd phenomenon known as Libyan Desert glass, a 2013 analysis of the Hypatia Stone discovered that it was of extraterrestrial origin, and was hypothesized to be a fragment of a cometary nucleus. However, a new analysis has found that the stone’s odd atomic composition doesn’t even match any known meteorite samples, implying that it is either from outside the Solar System, or it predates the formation of the Solar System itself.

Containing microscopic diamonds formed from a violent impact, the Hypatia Stone was presumed to be the product of the same celestial collision that formed Libyan Desert glass, fragments of natural glass that are found across the Eastern Sahara, the product of a meteorite or cometary impact that occurred 26 million years ago. But in studying the noble gases found in the cosmic pebble — helium, neon, argon, krypton and xenon — the research team from the University of Johannesburg found that the isotopic ratios of these gases pointed to an extra-solar origin for the rock.

"Even more unusual," explains lead researcher Jan Kramers, "the matrix contains a high amount of very specific carbon compounds, called polyaromatic hydrocarbons, or PAH, a major component of interstellar dust, which existed even before our solar system was formed.

"Interstellar dust is also found in comets and meteorites that have not been heated up for a prolonged period in their history," meaning that the body that the Hypatia Stone came from had been in deep space, away from a star that could have warmed it, for an unusual length of time.

And the surprises didn’t end there: pure metallic aluminum — an extremely rare occurrence in nature — was found in the stone, as was the prescience of a phosphorous-nickel compound that lacked any trace of iron, an occurrence unheard of in both terrestrial and extraterrestrial samples. This led the research team to hypothesize that while the stone itself probably formed as part of the early Solar System, the elements that make up the Hypatia Stone predate the formation of the Sun itself.

"Hypatia was formed in a cold environment, probably at temperatures below that of liquid nitrogen on Earth (-196ºC). In our solar system it would have been way further out than the asteroid belt between Mars and Jupiter, where most meteorites come from," Kramers explains.

"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. 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." 

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