Science: Samples collected from the near-Earth asteroid Ryugu have revealed clues about a primordial magnetic field that helped asteroids, planets and moons in our solar system develop. Analysis of three particles returned to Earth by Japan’s Hayabusa2 mission in 2020 found evidence of an ancient magnetic field preserved in the asteroid’s geological record, a new study reports.
“This nebular region disappeared about three to four million years after the formation of the solar system, and we are fascinated by how it played a role in early planet formation,” lead author Elias Mansbach, a postdoctoral researcher at the University of Cambridge in England, said in a statement. “But how far this magnetic field extended, and what role it played in more remote regions, is still uncertain, because not many samples have been found that can tell us about the outer solar system.”Astronomers believe Ryugu formed in the outskirts of the solar system about four billion years ago and then moved closer to the sun, eventually coming to its current orbit between Earth and Mars. This means the asteroid has been relatively untouched by processes that alter or erase the geological and magnetic record, such as intense heat or
The asteroid was placed into an instrument called a magnetometer, which measures the strength and direction of the sample’s magnetism. If the particles show a certain pattern or strength of magnetism, it indicates they have been exposed to a magnetic field at some point in their history, helping scientists determine whether an ancient magnetic field existed when the asteroid formed.
The research team then applied an alternating magnetic field to progressively demagnetize each sample, helping to precisely identify the original magnetic signal stored in the particles. This process, called progressive demagnetization, removes weaker, more recent magnetic imprints and retains only the strongest, most ancient magnetism, providing clear evidence of ancient magnetic conditions in the early solar system.
