Study of zircon crystals casts doubt on evidence for early development of magnetic field

January 3, 2019 by Bob Yirka, Phys.org report
Credit: CC0 Public Domain

A combined team of researchers from the University of Cambridge and the University of California has found evidence that casts doubt on the use of zircon crystals as evidence of early development of the Earth's magnetic field. In their paper published in Proceedings of the National Academy of Sciences, the group describes testing they conducted on the crystals and what they found.

Scientists have long been curious about the development of the Earth's —it is believed to be part of the process that made life possible on the planet because it shields the atmosphere from the solar wind. But it is not known when it first appeared. Scientists believe that the field exists due to the spin of the Earth's metal core, but that theory was tested when researchers found something intriguing when studying from Jack Hills in Western Australia. The crystals were found to be between 3.3 and 4.2 billion years old, suggesting they could offer evidence of conditions when the planet was still forming.

They noted that the crystals were magnetic, suggesting that they had been magnetized by a planetary magnetic field. But prior research has suggested the Earth's core did not harden until much later—thus, the magnetic field would have been created by a liquid core. In this new effort, the researchers claim to have found evidence that suggests the crystals could have become magnetized much later than their creation date, casting doubt on their use as evidence of a liquid core-generated magnetic field.

The researchers found nano-sized holes in the crystals that appeared to have resulted from radiation damage. That allowed magnetite to accumulate within the tiny holes long after the crystals had developed. The researchers note that magnetite is very easily magnetized (hence its name) and will retain magnetism for very long periods of time, as long as it is not exposed to temperatures above 550°C. This finding suggests that the magnetism in the crystals could have developed long after the crystals formed—and it prevents them from being used as evidence for the existence of a planetary magnetic field during its creation stages.

Explore further: Are Rossby waves to blame for Earth's magnetic field drifting westward?

More information: Fengzai Tang et al. Secondary magnetite in ancient zircon precludes analysis of a Hadean geodynamo, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1811074116

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Gorgar
2.3 / 5 (3) Jan 03, 2019
"They noted that the crystals were magnetic". That is quite vague. Do they understand the difference between magnetized objects and a magnet. It doesn't seem so. And no Fe. I'll bet they don't know what a magnetic field is.
rrwillsj
not rated yet Jan 03, 2019
G, I will be willing to consider your comment as a viable criticism of the research. When you reveal your credentials & show confirmed, repeatable research results that dispute the claims in this article.

The scientists may be using such terms as "magnetic" in ways that you do not understand. Not their problem. As long as peer review agrees with their interpretation.

This seems to be a common discordance between professionals & the general public. Just try & stay awake listening to lawyers dispute corporation laws... Major MEGO!

Or, for that matter? Have to listen to a HVAC repairman explain the excruciating details of why your building's repair invoice has a 60% overrun of the original cost estimate!
torbjorn_b_g_larsson
1 / 5 (1) Jan 03, 2019
"They noted that the crystals were magnetic". That is quite vague. Do they understand the difference between magnetized objects and a magnet. It doesn't seem so. And no Fe. I'll bet they don't know what a magnetic field is.


You should never take the word of a press release or - as here - a journalist - for the actual research. Go read the paper, then point to specific problems if any.

Also, magnetite in the title suggest without going into the paper that they are looking at Fe minerals.

Just for pun: 'Do you understand the difference between a science article and a press release or journalist write up? It doesn't seem so. And no reading comprehension. I'll bet you don't know what science is.'
Gorgar
not rated yet Jan 12, 2019
The scientists may be using such terms as "magnetic" in ways that you do not understand. Not their problem. As long as peer review agrees with their interpretation.
"This seems to be a common discordance between professionals & the general public. Just try & stay awake listening to lawyers dispute corporation laws... Major MEGO!
Or, for that matter? Have to listen to a HVAC repairman explain the excruciating details of why your building's repair invoice has a 60% overrun of the original cost estimate!"

I should have read the original article before spouting off. My bad. My credentials are bike mechanic. And I know what a magnetic field is. What are your credentials? Can you define a magnetic field in and of itself? Not too many people can. That is a huge problem in modern physics.
Gorgar
not rated yet Jan 12, 2019
I'll bet you don't know what science is.'


Yeah. My bad. I am just an "amateur fringe science guy". I should have read the original paper. I do however know what science is. Do you? Define a magnetic field. I am pushing people for this definition so they can look at many of their assumptions about what they think they know. Without an understanding of the magnetic field, one is not a scientist.

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