Rubble-pile asteroids form when asteroids collide and their shards reassemble into latest, shuffled asteroids. And after they do, based on a brand new study, they could give the renewed asteroid a brief magnetic field.
This result might address a mystery that has baffled astronomers for years: Some metallic meteorites hold traces of magnetism as in the event that they carry remnants of internal magnetic fields. That shouldn’t be possible. Even when a meteorite does contain iron, it is not expected to have a circulating dynamo, just like the one in Earth’s inner core, which scientists think is essential to generate a magnetic field.
“I had been aware of this puzzle for a while,” Zhongtian Zhang, a planetary scientist at Yale University, said in an announcement.
And as he studied rubble-pile asteroids, the puzzle returned to his mind. So, Zhang and fellow Yale planetary scientist David Bercovici turned to modeling asteroid collisions.
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When two iron-rich asteroids smashed into one another and scattered into shards, they found, a few of those shards would coalesce right into a chillier inner core that was coated by a hotter layer of molten rock. Then, if the shards were just the appropriate size, the cold core would start stripping elements, similar to sulfur, from the new liquid.
This model illustrated that the resulting heat transfer could create circulation sufficient to trigger a dynamo and, thus, a magnetic field. And if such a dynamo formed, it could last for hundreds of thousands of years — and its traces can be detectable by astronomers long afterward.
The study was published on July 31 within the journal Proceedings of the National Academy of Sciences.