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Speaker 1: Welcome to brain Stuff from How Stuff Works, Hey, brain Stuff,

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Speaker 1: Lauren bog Obam here. On February six, nineteen seventy one,

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Speaker 1: the late astronaut Alan Shepherd, the commander of NASA's Apollo

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Speaker 1: fourteen mission, was taking a walk on the Moon. He

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Speaker 1: and fellow space traveler Edgar Mitchell were out gathering rocks

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Speaker 1: around a depression called Cone Crater. To quote Shepherd himself,

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Speaker 1: many of these were hand sized grab samples, but the

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Speaker 1: pair took home some larger mementos. To one basketball sized

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Speaker 1: rock collected by Shepherd earned itself a nickname, Big Bertha,

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Speaker 1: officially known as Lunar Sample one four three to one.

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Speaker 1: Big Bertha ways about nineteen pounds that's nine kilograms, making

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Speaker 1: it the largest rock that Apollo fourteen brought back to

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Speaker 1: Earth and the third largest collected by any of the

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Speaker 1: Apollo missions. Although Shepherd found Big Bertha on the Moon,

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Speaker 1: that may not be where its story began. The rock

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Speaker 1: is a breccia, a hodgepodge of geologic fragments called clasts,

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Speaker 1: which are held together by a cement like mix. A

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Speaker 1: newly published hypothesis says that part of Big Birth of

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Speaker 1: formed billions of years ago right here on planet Earth.

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Speaker 1: In fact, despite the lunar connection, this could represent the

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Speaker 1: oldest Earth rock ever discovered. Big Birth's origins were the

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Speaker 1: focus of a study that was published in January in

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Speaker 1: the journal Earth and Planetary Science Letters. The papers authors

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Speaker 1: include an international team of geoscientists who looked at the

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Speaker 1: Moon rocks procured by Apollo fourteen, including lunar sample one

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Speaker 1: two one. For the most part, the classs on this

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Speaker 1: famous breccia are dark gray, but there's also a lightly

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Speaker 1: colored one that catches the eye. It's made of phil site,

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Speaker 1: a kind of volcanic rock that contains the minerals feldspar

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Speaker 1: and quartz. The light gray class, which is two centimeters

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Speaker 1: that's point seven inches across, is loaded with tiny zircon

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Speaker 1: crystals as well. Many zircons contain vital information about what

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Speaker 1: the environment was like when and where they formed. Close

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Speaker 1: inspection of the zircons in Big Bertha's light patch showed

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Speaker 1: that the crystals were produced by cool, oxygen rich magma.

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Speaker 1: Yet molten rock of this sort doesn't exist anywhere near

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Speaker 1: the Moon's surface. To find some, you'd need to travel

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Speaker 1: more than a hundred miles. That's a hundred and sixty

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Speaker 1: two kilometers below the surface of the Moon where Shepherd

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Speaker 1: and Mitchell found Big Bertha. So how did these zircons

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Speaker 1: and the class they belonged to end up on the surface.

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Speaker 1: A violent impact was probably involved. When a meteorite or

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Speaker 1: asteroid smacks into a planet or moon, it can transport

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Speaker 1: material that's buried deep under the crust up to the surface.

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Speaker 1: And as noted earlier, Big Bertha was found near an

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Speaker 1: impact crater, so case closed right, well maybe not. Cone

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Speaker 1: crater and expanse measuring about two hundred and fifty feet

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Speaker 1: that's seventy six deep and a thousand feet or three

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Speaker 1: hundred four wide, was created roughly twenty six million years ago.

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Speaker 1: Scientists think that the violent episode that left this depression

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Speaker 1: behind would have failed to dredge up any geologic material

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Speaker 1: lying more than forty five miles or seven two kilometers

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Speaker 1: underneath the Moon. Big Bertha's fellsite class could have originated

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Speaker 1: deep in a lunar magma pocket, but it doesn't seem likely.

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Speaker 1: The study authors think a different scenario is way more plausible.

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Speaker 1: Around twelve miles or nineteen kilometers below planet Earth's surface,

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Speaker 1: there's a supply of cool oxidized magma. This is exactly

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Speaker 1: the kind of raw material that probably made the zircons

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Speaker 1: on Big Birth as light patch, and by the way,

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Speaker 1: zircon crystals have a helpful habit of preserving uranium isotopes.

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Speaker 1: Those can be used for radiometric dating, a process that

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Speaker 1: tells us the Fellsite class is four point o to

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Speaker 1: four point one billion years old. Put both of these

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Speaker 1: clues together and a potential timeline of events emerges. According

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Speaker 1: to the hypothesis championed in the study, some of that

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Speaker 1: cool oxidized magma lying deep under Earth's continental crust hardened

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Speaker 1: into this class between four point o and four point

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Speaker 1: one billion years ago. We know that our planet was

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Speaker 1: besieged by media rites in those days, a process that

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Speaker 1: by the way, created a lot of old granites. Repeat

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Speaker 1: impacts would have driven the class ever closer to the surface,

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Speaker 1: until finally a projectile hit the Earth with enough force

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Speaker 1: to launch the Fell Site clear out into space. It's

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Speaker 1: estimated that four billion years ago, our moon was around

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Speaker 1: three times closer to Earth than it is right now.

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Speaker 1: The far flung class might have bridged the gap and

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Speaker 1: settled on the Moon, but around that time meteorites from

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Speaker 1: space also harassed the Moon, and approximately three point nine

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Speaker 1: billion years ago, one of these impacts could have partially

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Speaker 1: melted the class and driven it under the lunar surface,

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Speaker 1: where it merged with other classs and became part of

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Speaker 1: a breccia. Then, twenty six million years ago, the asteroid

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Speaker 1: strike that gave birth to the Cone Crater could have

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Speaker 1: set Big Birth of free, propelling it to the spot

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Speaker 1: where Alan Shepard came and grabbed it up one historic

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Speaker 1: day in If the fell Site class really did have

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Speaker 1: a terrestrial origin, then ironically enough, it might be the

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Speaker 1: oldest known rock from planet Earth. There's a four point

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Speaker 1: zero three billion year old rock from Canada's Northwest Territories

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Speaker 1: that's comparable in age, and over in Quebec, the Greenstone

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Speaker 1: Belt is at least three point nine billion years old.

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Speaker 1: Out in the jack Hills of Western Australia, scientists have

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Speaker 1: located zircons that formed roughly four point three seven billion

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Speaker 1: years ago, but these crystals seemingly detached from their original

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Speaker 1: rocks at some point. Big births Fellsite class and zircons

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Speaker 1: seemed to have formed simultaneously. Today's episode was written by

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Speaker 1: Mark Bancini and produced by Tyler Clang for iHeart Media

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Speaker 1: and how Stuff Works. For more on this and lots

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Speaker 1: of other far flung topics, visit our home planet, how

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