Ancient meteorites contain magnetic secrets about our solar system's past and our Earth's future, according to University of Cambridge.
Researchers have been able to ensnare and encapsulate the dying moments of an asteroid's magnetic field, and those moments have given scientists a look at what could happen as the Earth's core continues to freeze. The "magnetic memory" of ancient meteorites was read and the findings were published in the journal Nature on Jan. 22.
An intense beam of X-rays was used to pinpoint the exact moment an asteroid's magnetic field died, using the highest resolution paleomagnetic measures ever made, executed at the BESSY II synchrotron in Berlin, according to University of Cambridge.
"Observing magnetic fields is one of the few ways we can peek inside a planet," said study leader Richard Harrison of Cambridge's Department of Earth Sciences. "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 meteorites used for the study are called pallasites, made of iron and nickel, peppered with gem-quality silicate crystals and humble particles just 100 nanometres across - around one-thousandth the width of a human hair - of a magnetic mineral called tetrataenit. Tetrataenit is what holds the billions of years of magnetic memory of the meteorite, according to University of Cambridge.
"We're taking ancient magnetic field measurements in nanoscale materials to the highest ever resolution in order to piece together the magnetic history of asteroids - it's like a cosmic archaeological mission," said Ph.D. student and lead author James Bryson.
"It's funny that we study other bodies in order to learn more about the Earth," said Bryson. "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 Earth's core is freezing slowly, according to scientists, but how long until it kills the Earth's magnetic core is unknown. "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," said Harrison.
"There's no need to panic just yet, however," said Harrison. "The core won't completely freeze for billions of years, and chances are, the sun will get us first."
The research was funded by the European Research Council (ERC) and the Natural Environment Research Council (NERC).
