Researchers read magnetic messages hidden within ancient meteorites to peer into the early days of our solar system and even look into our planet's future.
A research team captured the dying moments of an asteroid's magnetic field to predict what could happen to Earth's magnetic core billions of years from now, the University of Cambridge reported.
The readings were taken from these tiny "space magnets" using an intense beam of x-rays, allowing them to get a snapshot of the exact moment the meteorite froze. They found the magnetic fields generated by these asteroids had much longer lives than previously predicted, and can last for several hundred million years after the object formed. The force was created through a similar mechanism to the one that causes the Earth's own magnetic field.
"Observing magnetic fields is one of the few ways we can peek inside a planet," said Richard Harrison of Cambridge's Department of Earth Sciences, who led the research. "It's long been assumed that metal-rich meteorites have poor magnetic memories, since they are primarily composed of iron, which has a terrible memory - you wouldn't ever make a hard drive out of iron, for instance. It was thought that the magnetic signals carried by metal-rich meteorites would have been written and rewritten many times during their lifetime, so no-one has ever bothered to study their magnetic properties in any detail."
The measurements were supported by computer simulations, which demonstrated the magnetic fields were created by compositional convection rather than thermal. These findings changed the researchers' perspective on the way magnetic fields were generated in the earliest days of the solar system.
The meteorites were created within the first few million years following the creation of our solar system and were heated by radioactive decay to temperatures that turned them into a liquid metal core surrounded by a rocky mantle. The swirling motion of this liquid coupled with the expulsion of sulphur from the inner core eventually generated a magnetic field.
"It's funny that we study other bodies in order to learn more about the Earth," said PhD student James Bryson, the paper's lead author. "Since asteroids are much smaller than the Earth, they cooled much more quickly, so these processes occur on shorter timescales, enabling us to study the whole process of core solidification."
The findings suggest the Earth's core only started to freeze relatively recently, as soon as less than a billion years ago.
"In our meteorites we've been able to capture both the beginning and the end of core freezing, which will help us understand how these processes affected the Earth in the past and provide a possible glimpse of what might happen in the future," Harrison said.
The Earth's core is believed to be freezing extremely slowly and is growing, meaning all of the liquid will eventually disappear.
"There's no need to panic just yet, however," Harrison concluded. "The core won't completely freeze for billions of years, and chances are, the Sun will get us first."
The findings were published in a recent edition of the journal Nature.
