Widespread magnetism dating from our solar system’s earliest beginnings some 4.57 billion years ago likely played a major role in creating orbital order out of chaos. But until now, magnetism’s role in shaping our solar system’s protoplanetary disk has largely remained a conundrum. That’s largely because researchers lacked the means to accurately measure leftover magnetism in ancient meteorites.
Yet in an unassuming basement laboratory in the department of earth sciences at the U.K.’s University of Oxford, at least one planetary scientist has begun a years-long effort to measure very faint magnetism in micrometer-sized meteorite samples.
The goal is to draw conclusions about just how the protoplanetary disk’s magnetism (the unseen physical phenomena that arise from the motion of electric charges) shaped the architecture of both our own solar system as well as extrasolar solar systems.
Here on Earth, our magnetic field has arguably played a role in our existence, James Bryson, a planetary scientist in the dept. of earth sciences at the University of Oxford, told me in his U.K. office. But we don’t know about how magnetism affected the very beginnings of our solar system, and that’s one of the key questions in planetary science, he says.
Bryson was the recent recipient of a 1.5-million-euro European Research Council five-year grant to study samples of ancient meteorites using a state-of-the-art magnetometer, now installed in the basement at Oxford.
Over the last decade, this new magnetometer—called a geo-quantum diamond microscope (geo-QDM)— has been proven to reliably measure weak magnetizations of sub-millimeter scale samples, Bryson noted in his project proposal.
This quantum diamond microscope instrument was installed in early 2022 and has been running since then, says Bryson. From about five meteorites, we could have up to ten subsamples from each meteorite; all of which have come from Antarctica, he says.
By measuring these samples, Bryson and colleagues are hoping they will be able to learn much about our solar system’s primordial magnetic field.
The behavior of this disk underpinned the process of planet building, Bryson wrote in the project’s proposal. Thus, this effort to measure the remanent (or residual) magnetism of samples of meteorites that have fallen to earth has the potential to revolutionize our understanding of the formation and habitability of the Earth, he noted in the proposal.
During the first five million years following the ignition of the sun, our solar system transformed from a chaotic protoplanetary disk of dust and gas into an organized collection of planets, asteroids, and comets, write the authors of a 2023 paper appearing in the journal Meteoritics and Planetary Science. The vast magnetic field that threaded the disk was able to influence the dynamics of dust and gas throughout the disk and had the potential to shape the rates and mechanisms by which the first planetary bodies formed and subsequently grew, the authors note.
To measure the remanent magnetism in tiny samples of meteorites, the geo-quantum diamond microscope must be shielded from earth’s own magnetic field. Inside the little room, earth’s magnetic field registers as much as a thousand times less than outside the laboratory.
That’s because we don’t want earth’s magnetic field interfering with our measurements of very weak magnetic samples, says Bryson.
Large Scale Dust
When the sun ignited, we had this colossal disc of dust and gas that was millions of kilometers big, says Bryson. Micrometer scale dust particles made up of all the atoms that we find inside planets —— iron, silicon, magnesium, and oxygen —- were all in that dust, he says.
Chaotic Beginnings
Within five million years of our solar system’s formation, our protoplanetary disk had transformed into millions of asteroids, comets, planets and moons, each on its own determined orbit, Bryson noted in his project proposal. Particles of dust and gas that made up the disk were charged and in constant motion, he wrote.
This whole protoplanetary disk of gas and dust generated a vast magnetic field which after only a few million years was swept away by the sun’s burgeoning solar wind.
How can remanents from such an ancient magnetic field be detected today?
We’re taking individual crystals that make these meteorites and measuring them piece by piece, so we can build up a much more complete understanding of how the magnetism in the early solar system was behaving, says Bryson. Then we’re going to tie all that together to try and say what role magnetic fields played during the entire planet building process, he says.
An Open Question
It’s an open question as to how much of an impact this paleomagnetic field had in orchestrating the architecture of our planetary system, says Bryson. Only in the last 10 years have we been able to say that a magnetic field that’s been measured in a meteorite corresponds to the field created by the protoplanetary disk, he says.
But such planetary magnetic fields aren’t a given.
Of the tens of thousands of rocky planetary bodies in our solar system, only earth, Mercury, Jupiter’s moons of Ganymede and possibly Io are generating detectable magnetic fields through core dynamo activity at the present day, Bryson and co-authors note in a 2019 paper appearing the journal Earth and Planetary Science Letters. Measurements of ancient terrestrial samples also suggest that earth has generated a continuous magnetic field for roughly the last three billion years, the authors note.
And once the team’s work is done?
We’ll hopefully have a more complete idea of how our protoplanetary disk’s Magnetic field varied in time and in space, and what role that could have played in planet building, says Bryson.
The Bottom Line?
To determine whether there was a unique feature in earth’s early history that potentially led to it being the single known planet that supports life, Bryson writes in his original project proposal.
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