Speaker 1: Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff, Lauren
Speaker 1: vogelbomb here with a classic episode from our podcast's archives.
Speaker 1: The substance of the Earth's crust is changing all the time,
Speaker 1: though not usually on a timescale that we really observe.
Speaker 1: You know, Rivers and lakes and even oceans carve out
Speaker 1: territory and then recede. Mountains rise and fall, all impacting
Speaker 1: the makeup of Earth's surface in traceable ways. Back in
Speaker 1: twenty nineteen, researchers announced that they discovered what's likely the
Speaker 1: oldest surviving bit of rock ever found, and they found
Speaker 1: it in a piece of moon rock. Hey brain Stuff,
Speaker 1: laurenvoglebomb here. On February sixth, nineteen seventy one, the late
Speaker 1: astronaut Alan Shepherd, the commander of NASA's Apollo fourteen mission,
Speaker 1: was taking a walk on the Moon. He and fellow
Speaker 1: space traveler Edgar Mitchell were out gathering rocks around a
Speaker 1: depression called Cone Crater. To quote Sheppard himself, Many of
Speaker 1: these were hand sized grab samples, but the pair took
Speaker 1: home some larger mementos too. One basketball sized rock collected
Speaker 1: by Shepherd earned itself a nickname Big Bertha, officially known
Speaker 1: as Lunar Sample one four three two one. Big Bertha
Speaker 1: weighs about nineteen pounds that's nine kilograms, making it the
Speaker 1: largest rock that Apollo fourteen brought back to Earth and
Speaker 1: the third largest collected by any of the Apollo missions.
Speaker 1: Although Shepherd found Big Bertha on the Moon, that may
Speaker 1: not be where its story began. The rock is a breccia,
Speaker 1: a hodgepodge of geologic fragments called clasts, which are held
Speaker 1: together by a cement like mix. A newly published hypothesis
Speaker 1: says that part of Big Bertha formed billions of years
Speaker 1: ago right here on planet Earth. In fact, despite the
Speaker 1: lunar connection, this could represent the oldest Earth rock ever discovered.
Speaker 1: Big Bertha's origins were the focus of a study that
Speaker 1: was published in January in the journal Earth and Planetary
Speaker 1: Science Letters. The paper's authors include an international team of
Speaker 1: geoscientists who looked the Moon rocks procured by Apollo fourteen,
Speaker 1: including Lunar Sample one four three two one. For the
Speaker 1: most part, the clasts on this famous breccia are dark gray,
Speaker 1: but there's also a lightly colored one that catches the eye.
Speaker 1: It's made of fill sight a kind of volcanic rock
Speaker 1: that contains the minerals feldspar, and quartz. The light gray class,
Speaker 1: which is two centimeters that's point seven inches across, is
Speaker 1: loaded with tiny zircon crystals as well. Many zircons contain
Speaker 1: vital information about what the environment was like, when and
Speaker 1: where they formed. Close inspection of the zircons in Big
Speaker 1: Bertha's light patch showed that the crystals were produced by cool,
Speaker 1: oxygen rich magma. Yet molten rock of this sort doesn't
Speaker 1: exist anywhere near the Moon's surface. To find some, you'd
Speaker 1: need to travel more than one hundred miles that's one
Speaker 1: hundred and sixty two kilometers below the surface of the
Speaker 1: Moon where Shepherd and Mitchell found Big Bertha. So how
Speaker 1: did these zircons and the class they belong to end
Speaker 1: up on the surface. A violent impact was probably involved.
Speaker 1: When a meteorite or asteroid smacks into a planet or moon,
Speaker 1: it can transport material that's buried deep under the crust
Speaker 1: up to the surface. And as noted earlier, Big Bertha
Speaker 1: was found near an impact crater, So case closed, right, Well,
Speaker 1: maybe not Cone crater, an expanse measuring about two hundred
Speaker 1: and fifty feet to that seventy six meters deep and
Speaker 1: one thousand feet or three hundred and four meters wide
Speaker 1: was created roughly twenty six million years ago. Scientists think
Speaker 1: that the violent episode that left this depression behind would
Speaker 1: have failed to dredge up any geologic material lying more
Speaker 1: than forty five miles or seventy two kilometers underneath the Moon.
Speaker 1: A Big Berth Is Fell site classed 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 Berth 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 Fell site clast is four point oh
Speaker 1: to four point one billion years old. Put both of
Speaker 1: these clues together and a potential timeline of events emerges.
Speaker 1: According to the hypothesis championed in the study. Some of
Speaker 1: that cool oxidized magma lying deep under Earth's continental crust
Speaker 1: hardened into this clast between four point oh and four
Speaker 1: point one billion years ago. We know that our planet
Speaker 1: was besieged by meteorites 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 clast 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 a lunar surface,
Speaker 1: where it merged with other clasts and became part of Abreccia. Then,
Speaker 1: twenty six million years ago, the asteroid strike that gave
Speaker 1: birth to the Cone Crater could have set Big Berth
Speaker 1: a free, propelling it to the spot where Alan Shepherd
Speaker 1: came and grabbed it up one historic day in nineteen
Speaker 1: seventy one. If the felsite class really did have a
Speaker 1: terrestrial origin, then, ironically enough, it might be the oldest
Speaker 1: known rock from planet Earth. There's a four point zero
Speaker 1: three billion year old rock from Canada's Northwest Territories that's
Speaker 1: comparable in age and over in Quebec, the Greenstone Belt
Speaker 1: is at least three point nine billion years old. Out
Speaker 1: in the jack Hills of Western Australia, scientists have located
Speaker 1: zircons that formed roughly four point three seven billion years ago,
Speaker 1: but these crystals sely detached from their original rocks at
Speaker 1: some point. Big Birth is felsite class and at zircons
Speaker 1: seem to have formed simultaneously. Today's episode is based on
Speaker 1: the article Earth's oldest rock may have been discovered on
Speaker 1: the Moon on HowStuffWorks dot com, written by Mark Mancini.
Speaker 1: Brain Stuff is production of iHeartRadio in partnership with how
Speaker 1: Stuffworks dot Com, and it is produced by Tyler Klang.
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