WEBVTT - Was Earth's Oldest Rock Found on the Moon?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works, Hey, brain Stuff,

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<v Speaker 1>Lauren bog Obam here. On February six, nineteen seventy one,

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<v Speaker 1>the late astronaut Alan Shepherd, the commander of NASA's Apollo

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<v Speaker 1>fourteen mission, was taking a walk on the Moon. He

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<v Speaker 1>and fellow space traveler Edgar Mitchell were out gathering rocks

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<v Speaker 1>around a depression called Cone Crater. To quote Shepherd himself,

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<v Speaker 1>many of these were hand sized grab samples, but the

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<v Speaker 1>pair took home some larger mementos. To one basketball sized

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<v Speaker 1>rock collected by Shepherd earned itself a nickname, Big Bertha,

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<v Speaker 1>officially known as Lunar Sample one four three to one.

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<v Speaker 1>Big Bertha ways about nineteen pounds that's nine kilograms, making

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<v Speaker 1>it the largest rock that Apollo fourteen brought back to

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<v Speaker 1>Earth and the third largest collected by any of the

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<v Speaker 1>Apollo missions. Although Shepherd found Big Bertha on the Moon,

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<v Speaker 1>that may not be where its story began. The rock

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<v Speaker 1>is a breccia, a hodgepodge of geologic fragments called clasts,

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<v Speaker 1>which are held together by a cement like mix. A

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<v Speaker 1>newly published hypothesis says that part of Big Birth of

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<v Speaker 1>formed billions of years ago right here on planet Earth.

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<v Speaker 1>In fact, despite the lunar connection, this could represent the

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<v Speaker 1>oldest Earth rock ever discovered. Big Birth's origins were the

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<v Speaker 1>focus of a study that was published in January in

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<v Speaker 1>the journal Earth and Planetary Science Letters. The papers authors

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<v Speaker 1>include an international team of geoscientists who looked at the

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<v Speaker 1>Moon rocks procured by Apollo fourteen, including lunar sample one

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<v Speaker 1>two one. For the most part, the classs on this

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<v Speaker 1>famous breccia are dark gray, but there's also a lightly

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

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<v Speaker 1>a kind of volcanic rock that contains the minerals feldspar

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<v Speaker 1>and quartz. The light gray class, which is two centimeters

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<v Speaker 1>that's point seven inches across, is loaded with tiny zircon

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<v Speaker 1>crystals as well. Many zircons contain vital information about what

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<v Speaker 1>the environment was like when and where they formed. Close

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<v Speaker 1>inspection of the zircons in Big Bertha's light patch showed

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<v Speaker 1>that the crystals were produced by cool, oxygen rich magma.

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<v Speaker 1>Yet molten rock of this sort doesn't exist anywhere near

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

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<v Speaker 1>more than a hundred miles. That's a hundred and sixty

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<v Speaker 1>two kilometers below the surface of the Moon where Shepherd

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<v Speaker 1>and Mitchell found Big Bertha. So how did these zircons

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<v Speaker 1>and the class they belonged to end up on the surface.

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<v Speaker 1>A violent impact was probably involved. When a meteorite or

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<v Speaker 1>asteroid smacks into a planet or moon, it can transport

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<v Speaker 1>material that's buried deep under the crust up to the surface.

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<v Speaker 1>And as noted earlier, Big Bertha was found near an

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<v Speaker 1>impact crater, so case closed right, well maybe not. Cone

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<v Speaker 1>crater and expanse measuring about two hundred and fifty feet

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<v Speaker 1>that's seventy six deep and a thousand feet or three

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<v Speaker 1>hundred four wide, was created roughly twenty six million years ago.

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<v Speaker 1>Scientists think that the violent episode that left this depression

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<v Speaker 1>behind would have failed to dredge up any geologic material

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<v Speaker 1>lying more than forty five miles or seven two kilometers

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<v Speaker 1>underneath the Moon. Big Bertha's fellsite class could have originated

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

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<v Speaker 1>The study authors think a different scenario is way more plausible.

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<v Speaker 1>Around twelve miles or nineteen kilometers below planet Earth's surface,

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<v Speaker 1>there's a supply of cool oxidized magma. This is exactly

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<v Speaker 1>the kind of raw material that probably made the zircons

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<v Speaker 1>on Big Birth as light patch, and by the way,

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<v Speaker 1>zircon crystals have a helpful habit of preserving uranium isotopes.

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<v Speaker 1>Those can be used for radiometric dating, a process that

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<v Speaker 1>tells us the Fellsite class is four point o to

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<v Speaker 1>four point one billion years old. Put both of these

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<v Speaker 1>clues together and a potential timeline of events emerges. According

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<v Speaker 1>to the hypothesis championed in the study, some of that

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<v Speaker 1>cool oxidized magma lying deep under Earth's continental crust hardened

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<v Speaker 1>into this class between four point o and four point

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<v Speaker 1>one billion years ago. We know that our planet was

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<v Speaker 1>besieged by media rites in those days, a process that

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<v Speaker 1>by the way, created a lot of old granites. Repeat

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<v Speaker 1>impacts would have driven the class ever closer to the surface,

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<v Speaker 1>until finally a projectile hit the Earth with enough force

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<v Speaker 1>to launch the Fell Site clear out into space. It's

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<v Speaker 1>estimated that four billion years ago, our moon was around

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<v Speaker 1>three times closer to Earth than it is right now.

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<v Speaker 1>The far flung class might have bridged the gap and

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<v Speaker 1>settled on the Moon, but around that time meteorites from

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<v Speaker 1>space also harassed the Moon, and approximately three point nine

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<v Speaker 1>billion years ago, one of these impacts could have partially

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<v Speaker 1>melted the class and driven it under the lunar surface,

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<v Speaker 1>where it merged with other classs and became part of

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<v Speaker 1>a breccia. Then, twenty six million years ago, the asteroid

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<v Speaker 1>strike that gave birth to the Cone Crater could have

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<v Speaker 1>set Big Birth of free, propelling it to the spot

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<v Speaker 1>where Alan Shepard came and grabbed it up one historic

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<v Speaker 1>day in If the fell Site class really did have

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<v Speaker 1>a terrestrial origin, then ironically enough, it might be the

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<v Speaker 1>oldest known rock from planet Earth. There's a four point

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<v Speaker 1>zero three billion year old rock from Canada's Northwest Territories

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<v Speaker 1>that's comparable in age, and over in Quebec, the Greenstone

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<v Speaker 1>Belt is at least three point nine billion years old.

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<v Speaker 1>Out in the jack Hills of Western Australia, scientists have

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<v Speaker 1>located zircons that formed roughly four point three seven billion

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<v Speaker 1>years ago, but these crystals seemingly detached from their original

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<v Speaker 1>rocks at some point. Big births Fellsite class and zircons

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<v Speaker 1>seemed to have formed simultaneously. Today's episode was written by

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<v Speaker 1>Mark Bancini and produced by Tyler Clang for iHeart Media

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<v Speaker 1>and how Stuff Works. For more on this and lots

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<v Speaker 1>of other far flung topics, visit our home planet, how

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<v Speaker 1>stuff Works dot com