Meteorite's Magnetic Fields Sheds Light on Solar System's Birth

New analyses of a primitive meteorite's magnetic fields, frozen within the space rock's grains, are helping to shed light on the solar system's birth and how it has evolved over time, a new study describes.

The studied meteorite, named Semarkona, belongs to a class of the most primitive and least altered type of meteorites, called chondrites. Built mostly of small stony grains, they are barely a millimeter in diameter, but nonetheless the fact that they date back to the birth of the solar system makes them incredibly valuable to scientists.

Though the solar system formed 4.5 billion years ago, this messy process left behind remnants of its formation, some in the form of tiny grains, or chondrules, in meteorites.

Described in the journal Science, chondrules formed after droplets of molten rock - which melted in the dusty gas cloud, or solar nebula, that surrounded the young Sun - cooled and crystallized. During this cooling process, iron-bearing minerals within the chondrules became magnetized, leading to the magnetic fields that scientists study today.

Researchers from Arizona State University decided to study the chondrule grains from the meteorite Semarkona, named for the place in India where it fell in 1940. By mapping its magnetic fields, the new study found that they measured at about 54 microtesla, similar to the magnetic field at Earth's surface, which ranges from 25 to 65 microtesla.

"This is the first really accurate and reliable measurement of the magnetic field in the gas from which our planets formed," co-author Steve Desch said in a statement.

Given that the measured magnetic field strength of Semarkona is about 54 microtesla, and that the shock wave of the solar nebula surrounding the Sun at the beginning of the Universe could amplify this magnetic field by up to 30 times, scientists believe that the "nebula was probably in the range of 5 to 50 microtesla," according to Desch.

This reinforces the idea that shocks melted the chondrules in the solar nebula at about the location of today's asteroid belt, which lies some two to four times farther from the Sun than Earth now orbits.