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  • From snazzy banded agates to volcanic elephants, there are some pretty weird rocks out there.

  • But the weirdest ones geologists find might be those that fall from space.

  • And one called the Hypatia stone could be, the strangest of them all.

  • In fact, all signs currently suggest that this rock's origin story is older than the solar system itself!

  • And if it's notwell, we're going to have to rethink what we know about our cosmic neighborhood.

  • The Hypatia stone was found in 1996 by a geologist in the southwest Egyptian Sahara.

  • It's named after the first female astronomer and mathematician who managed to make the history books.

  • The stone was discovered in fragments no bigger than a centimeter across,

  • and in total, the pieces added up to a volume only about 20 cubic centimeters.

  • Technically, it isn't considered a meteorite,

  • because the Meteoritical Society requires 20% of a rock's original mass to be present to earn that title.

  • And scientists have chipped this thing apart and sent pieces to so many labs that it no longer fits the bill.

  • But it's definitely from space.

  • When its extraterrestrial origins were confirmed in 2013,

  • scientists assumed it was the very first comet nucleus, or the rocky, central part of a comet, to be found on Earth.

  • But its story is a bit more complicated. And interesting.

  • First, exactly when the stone struck our planet is hard to pin down.

  • It was found in an area of the Sahara full of these special rocks called Libyan Desert Glass,

  • which are believed to have been created by a meteorite impact 28-ish million years ago.

  • But the relationship between the Hypatia stone and this glass is far from certain.

  • We're also not positive how big this rock was when it initially entered Earth's atmosphere.

  • Based on its amount of a certain type of neon,

  • we think it couldn't have been more than several meters in diameter.

  • Or, if it were bigger, the Hypatia stone itself had to have come from the upper few meters.

  • These basic details are important to figure out,

  • but what's really strange about the Hypatia stone is what researchers discovered once they started analyzing its composition.

  • Because from what we can tell, Hypatia's chemical makeup isn't just out of this world.

  • It's out of the entire solar system!

  • See, everything in our neighborhood formed out of the same cloud of dust and gas.

  • And since astronomers believe that the cloud was relatively homogenous,

  • the rocky bits that formed should all, on the whole, have roughly the same chemical makeup.

  • But in 2015, scientists revealed that the Hypatia stone is different.

  • It has a composition unlike any other solar system object studied in a lab.

  • For example, its amount of the isotope nitrogen-15, a type of nitrogen with an extra neutron,

  • was way off for it to be from a standard comet.

  • Astronomers also found a type of xenon that's created when one iodine isotope,

  • one that predates the solar system, undergoes radioactive decay.

  • So something about this thing totally isn't normal.

  • And this year, we got an even deeper analysis.

  • In February 2018, a team of astronomers announced that they'd identified two separate,

  • yet intermingled, matrices in the Hypatia stone,

  • kinda like finding two different batters in the same cake.

  • The matrices themselves had to have formed when the solar system did,

  • because Hypatia needed a cloud of dense interstellar dust to form.

  • But they had the opposite composition of carbon and silicon that common meteorites do.

  • The ones we normally see, called chondritic meteorites, are low in carbon and high in silicon,

  • but Hypatia has lots of carbon and basically no silicon.

  • So again, not normal.

  • But what was even more surprising about this analysis is

  • that one of those matrices was also chock-full of deposits, or inclusions.

  • And each of them likely existed before the entire solar system!

  • This includes moissanite grains, which are commonly a small part of some meteorites,

  • but are considered to be mostly pre-solar.

  • They also found a nugget of pure metallic aluminum in Hypatia,

  • which is super rare in solar system rocks.

  • And there were also a lot of these organic molecules called polycyclic aromatic hydrocarbons,

  • or PAHs, which are a big part of interstellar dust.

  • PAHs are also inside certain comets and asteroids, so finding them in the Hypatia stone wasn't unusual,

  • but the abundance of them was.

  • Conveniently, these PAHs were also a big reason we're able to study the stone today.

  • Many of the them were turned into a crust of tiny diamonds, likely when Hypatia crashed into the Earth,

  • and they protected and preserved the inside of the rock for millions of years.

  • But that doesn't explain where they came from.

  • And there were other compounds found that haven't been observed in any studied space rock, too.

  • So the Hypatia stone is still completely unique.

  • At least as far as we know.

  • Although it's a pretty compelling case,

  • we'll still need further analysis of certain isotopes before we can definitively say

  • that parts of this rock existed before the Sun.

  • But the exciting news is, the authors of that 2018 paper hope to get that research out ASAP,

  • so we'll keep you updated.

  • So, even if Hypatia turns out not to be pre-solar, that might be even weirder.

  • That would imply that the early solar system wasn't homogeneous after all,

  • despite the generally accepted view.

  • So we'd have to change the way we think about our neighborhood's history.

  • Based on what we know so far,

  • astronomers can at least tell that the stone had to have formed in a super cold environment,

  • one below about -200°C.

  • So if it is from around here after all,

  • that likely means Hypatia had to have formed out in the Kuiper Belt where Pluto lives,

  • or even farther away, like in the distant, mysterious Oort cloud.

  • We don't actually know a lot about the composition of all the bodies that far out there,

  • so it could totally turn out that there are other Hypatia-like space rocks.

  • Mosty, all this means means we just have to keep looking.

  • But no matter what the answer to this mystery is, we're gonna learn something cool.

  • Thanks for watching this episode of SciShow Space!

  • If you'd like to keep exploring the mysteries of the universe with us,

  • and learning some cool stuff along the way,

  • you can go to youtube.com/scishowspace and subscribe.

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The Strange Case of the Hypatia Stone

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    林宜悉 posted on 2020/03/30
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