Speaker 1: Welcome to brain Stuff from How Stuff Works, Hey, brain Stuff,
Speaker 1: Lauren bog Obam here. On February six, nineteen seventy one,
Speaker 1: the late astronaut Alan Shepherd, the commander of NASA's Apollo
Speaker 1: fourteen mission, was taking a walk on the Moon. He
Speaker 1: and fellow space traveler Edgar Mitchell were out gathering rocks
Speaker 1: around a depression called Cone Crater. To quote Shepherd himself,
Speaker 1: many of these were hand sized grab samples, but the
Speaker 1: pair took home some larger mementos. To one basketball sized
Speaker 1: rock collected by Shepherd earned itself a nickname, Big Bertha,
Speaker 1: officially known as Lunar Sample one four three to one.
Speaker 1: Big Bertha ways about nineteen pounds that's nine kilograms, making
Speaker 1: it the largest rock that Apollo fourteen brought back to
Speaker 1: Earth and the third largest collected by any of the
Speaker 1: Apollo missions. Although Shepherd found Big Bertha on the Moon,
Speaker 1: that may not be where its story began. The rock
Speaker 1: is a breccia, a hodgepodge of geologic fragments called clasts,
Speaker 1: which are held together by a cement like mix. A
Speaker 1: newly published hypothesis says that part of Big Birth of
Speaker 1: formed billions of years ago right here on planet Earth.
Speaker 1: In fact, despite the lunar connection, this could represent the
Speaker 1: oldest Earth rock ever discovered. Big Birth's origins were the
Speaker 1: focus of a study that was published in January in
Speaker 1: the journal Earth and Planetary Science Letters. The papers authors
Speaker 1: include an international team of geoscientists who looked at the
Speaker 1: Moon rocks procured by Apollo fourteen, including lunar sample one
Speaker 1: two one. For the most part, the classs on this
Speaker 1: famous breccia are dark gray, but there's also a lightly
Speaker 1: colored one that catches the eye. It's made of phil site,
Speaker 1: a kind of volcanic rock that contains the minerals feldspar
Speaker 1: and quartz. The light gray class, which is two centimeters
Speaker 1: that's point seven inches across, is loaded with tiny zircon
Speaker 1: crystals as well. Many zircons contain vital information about what
Speaker 1: the environment was like when and where they formed. Close
Speaker 1: inspection of the zircons in Big Bertha's light patch showed
Speaker 1: that the crystals were produced by cool, oxygen rich magma.
Speaker 1: Yet molten rock of this sort doesn't exist anywhere near
Speaker 1: the Moon's surface. To find some, you'd need to travel
Speaker 1: more than a hundred miles. That's a hundred and sixty
Speaker 1: two kilometers below the surface of the Moon where Shepherd
Speaker 1: and Mitchell found Big Bertha. So how did these zircons
Speaker 1: and the class they belonged to end up on the surface.
Speaker 1: A violent impact was probably involved. When a meteorite or
Speaker 1: asteroid smacks into a planet or moon, it can transport
Speaker 1: material that's buried deep under the crust up to the surface.
Speaker 1: And as noted earlier, Big Bertha was found near an
Speaker 1: impact crater, so case closed right, well maybe not. Cone
Speaker 1: crater and expanse measuring about two hundred and fifty feet
Speaker 1: that's seventy six deep and a thousand feet or three
Speaker 1: hundred four wide, was created roughly twenty six million years ago.
Speaker 1: Scientists think that the violent episode that left this depression
Speaker 1: behind would have failed to dredge up any geologic material
Speaker 1: lying more than forty five miles or seven two kilometers
Speaker 1: underneath the Moon. Big Bertha's fellsite class could have originated
Speaker 1: deep in a lunar magma pocket, but it doesn't seem likely.
Speaker 1: The study authors think a different scenario is way more plausible.
Speaker 1: Around twelve miles or nineteen kilometers below planet Earth's surface,
Speaker 1: there's a supply of cool oxidized magma. This is exactly
Speaker 1: the kind of raw material that probably made the zircons
Speaker 1: on Big Birth as light patch, and by the way,
Speaker 1: zircon crystals have a helpful habit of preserving uranium isotopes.
Speaker 1: Those can be used for radiometric dating, a process that
Speaker 1: tells us the Fellsite class is four point o to
Speaker 1: four point one billion years old. Put both of these
Speaker 1: clues together and a potential timeline of events emerges. According
Speaker 1: to the hypothesis championed in the study, some of that
Speaker 1: cool oxidized magma lying deep under Earth's continental crust hardened
Speaker 1: into this class between four point o and four point
Speaker 1: one billion years ago. We know that our planet was
Speaker 1: besieged by media rites in those days, a process that
Speaker 1: by the way, created a lot of old granites. Repeat
Speaker 1: impacts would have driven the class ever closer to the surface,
Speaker 1: until finally a projectile hit the Earth with enough force
Speaker 1: to launch the Fell Site clear out into space. It's
Speaker 1: estimated that four billion years ago, our moon was around
Speaker 1: three times closer to Earth than it is right now.
Speaker 1: The far flung class might have bridged the gap and
Speaker 1: settled on the Moon, but around that time meteorites from
Speaker 1: space also harassed the Moon, and approximately three point nine
Speaker 1: billion years ago, one of these impacts could have partially
Speaker 1: melted the class and driven it under the lunar surface,
Speaker 1: where it merged with other classs and became part of
Speaker 1: a breccia. Then, twenty six million years ago, the asteroid
Speaker 1: strike that gave birth to the Cone Crater could have
Speaker 1: set Big Birth of free, propelling it to the spot
Speaker 1: where Alan Shepard came and grabbed it up one historic
Speaker 1: day in If the fell Site class really did have
Speaker 1: a terrestrial origin, then ironically enough, it might be the
Speaker 1: oldest known rock from planet Earth. There's a four point
Speaker 1: zero three billion year old rock from Canada's Northwest Territories
Speaker 1: that's comparable in age, and over in Quebec, the Greenstone
Speaker 1: Belt is at least three point nine billion years old.
Speaker 1: Out in the jack Hills of Western Australia, scientists have
Speaker 1: located zircons that formed roughly four point three seven billion
Speaker 1: years ago, but these crystals seemingly detached from their original
Speaker 1: rocks at some point. Big births Fellsite class and zircons
Speaker 1: seemed to have formed simultaneously. Today's episode was written by
Speaker 1: Mark Bancini and produced by Tyler Clang for iHeart Media
Speaker 1: and how Stuff Works. For more on this and lots
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