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