Planet Earth was jabbed in the eye 65 million years ago—an asteroid dropped from the cosmic vault and KO’d the dinosaurs. The scar can still be seen today, just off the coast of the Yucatan Peninsula. Earth was involved in another brawl much earlier in it’s boxing career. Thea, a young proto-planet, delivered a glancing blow across the jaw. Theia wasn’t a lightweight asteroid, either! The heavy hitter was about the size of Mars, and if Theia landed a solid uppercut, Earth’s face would have exploded into 14 bazillion pieces.
…that didn’t happen.
The material that was blasted into space eventually coalesced to form Earth’s Moon. The Moon was baptized by a collision. Literally.
Turn It Up To Eleven
Accretion is an astronomical process which involves space rocks bashing their heads against each other. Lot of ’em. A mote of dust grows fatter and fatter as it smashes it’s dense head against everything in it’s path. Cosmic headbangers form most pits inside accretion disks. Accretion disks have been directly observed around other stars, so headbanging is not just a local phenomenon—the entire universe appears to be a fan of heavy metal.
Do you see that orange Frisbee toward the upper right-hand corner? That’s a certified accretion disk—dusty material that was leftover after the star ( IRAS 05413-0104) began to shed its light. Wanna guess what’s inside that accretion disk? That’s right! Cosmic headbangers. Can respectable planets form inside the accretion disk? Probably. Perhaps. Who knows.
We do know this—at least 3000 exoplanets have been discovered. Accretions disks and planetary formation appear to be correlated.
You’re probably still a little skeptical, right? Astronomer’s not only discovered an exoplanet orbiting Fomalhault, but they also photographed a ring of celestial garbage. Take a gander at that hot mess. Star formation and headbanger collisions produce dust, just like remnants that are leftover after a rock show…beer cups…cigarette filters…burnt rolling papers…half-eaten hotdogs…possibly a bra…or a leopard print thong (if you’re lucky).
Is it possible for a rock concert not to have those remnants? Who knows.
Gas giants are not afraid to party down inside a mosh pit. Rocky planets have a solid head, however, that doesn’t mean a puffy planet can’t crack some skulls! Gas giants are large and in charge—their unequaled gravitational pull picks a fight with nearby headbangers. Jupiter was caught banging its cloudy head against Comet Shoemaker-Levy 9. The entire rock show was recorded in 1994, and no one needed to buy tickets.
Earth is still bangin’ it’s head against rocks. Fist-sized meteorites smack into Earth everyday, so accretion is technically still occurring. Many people are unaware of Earth’s eating habits: 40,000 tonnes of dust accumulates around its planetary waistline…every year. Shooting stars must be tasty.
Stony meteorites are the most numerous cosmic headbangers which continue to pummel Earth. Meteorites are mere fragments of their former selves. Most meteorites are associated with specific asteroids. An asteroid’s rocky skin shreds against Earth’s dense atmosphere, and the resulting road rash strips away pieces of material. Meteorites are typically located inside ‘strewn fields’ which resulted from an asteroid blazing a path of hell through Earth’s atmosphere. Some meteorites contain mostly iron, or perhaps a mixture of rock and metal, however, those types of meteorites are relatively rare.
Is there a cosmic headbanger capable of leaving a significant bruise? Yup! Respectable asteroids and comets still intersect Earth’s orbit, and that means a collision is always possible. We may not know what inspired every extinction event, but sometimes when headbangers rock out—life must pay for the ticket.
…Hey! Do you need a meteorite photograph?
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