Microscopic minerals discovered from an old outcrop of Jack Hills in Western Australia have been the focus of considerable geological investigation, as they appear to contain remnants of the Earth’s magnetic field dating back as long as 4.2 billion years.
That’s over a billion years earlier than the magnetic field was previously supposed to have originated, and nearly as old as the planet itself.
However, as intriguing as this genesis narrative may be, evidence to the contrary has now been discovered by an MIT-led research. The scientists analyzed the same sort of crystals, called zircons, unearthed from the same outcrop in an article published in Science Advances, and determined that the zircons they gathered are untrustworthy as recorders of ancient magnetic fields.
To put it another way, it’s still up in the air whether the Earth’s magnetic field existed before 3.5 billion years ago.
Caue Borlina, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, says, “There is no significant evidence of a magnetic field earlier to 3.5 billion years ago, and even if there was a field, it will be very difficult to uncover evidence for it in Jack Hills zircons” (EAPS). “It’s a significant outcome in the sense that we now know what not to look for.”
A field, stirred up
The magnetic field of the Earth is assumed to have a key role in making the planet habitable. A magnetic field not only directs the movement of our compass needles, but it also acts as a barrier, deflecting solar wind that would otherwise eat away at the atmosphere.
The Earth’s magnetic field is currently fueled by the solidification of the planet’s molten iron core, according to scientists. The surrounding liquid iron is stirred up by the cooling and crystallization of the core, resulting in intense electric currents that form a magnetic field that stretches far into space. The geodynamo is the name for this magnetic field.
The Earth’s magnetic field existed at least 3.5 billion years ago, according to multiple lines of evidence. The planet’s core, on the other hand, is estimated to have begun hardening only 1 billion years ago, implying that the magnetic field must have been driven by some other force before then. Identifying the precise moment when the magnetic field created could aid scientists in determining what caused it in the first place.
According to Borlina, the genesis of Earth’s magnetic field may shed light on the early conditions under which Earth’s first life forms emerged.
“Life began to emerge in the Earth’s first billion years, between 4.4 billion and 3.5 billion years,” Borlina explains. “Having a magnetic field at the time has various consequences for the environment in which life first appeared on Earth. That is the driving force behind our efforts.”