Scientists’ Ice Findings Could Help Measure Earth’s Magnetic History

Share this article

Among other things, the history of our planet has been written in the periodic reversal of its magnetic poles. Scientists at the Weizmann Institute of Science have now proposed a new means of reading this historic record: in ice.

Their findings, recently reported in Earth and Planetary Science Letters, could lead to a refined probing of ice cores and could be applied to understanding the magnetic history of other bodies in our solar system, including Mars and Jupiter’s moon Europa.

The idea for investigating a possible connection between ice and Earth’s magnetic history arose far from the source of the planet’s ice – on the sunny isle of Corsica, where Professor Oded Aharonson of the Institute’s Earth and Planetary Sciences Department, was attending a conference on magnetism.

The researchers at the conference were there to discuss the field known as paleo-magnetism, which is mostly studied through flakes magnetic minerals that have been trapped either in rocks or cores drilled through ocean sediments. Such particles get aligned with the Earth’s magnetic field at the time they are trapped in place, and even millions of years later, researchers can test their magnetic north-south alignment and understand the position of the Earth’s magnetic poles at that distant time.

The latter gave Aharonson the idea that if small amounts of magnetic materials could be sensed in ocean sediments, maybe they could also be found trapped in ice and measured.

Some ice frozen in glaciers in places like Greenland or Alaska is many millennia old, and layered like tree rings. Ice cores drilled through these are investigated for signs of such things as planetary warming or ice ages. Why not reversals in the magnetic field as well?

The first question that Aharonson and his student, Yuval Grossman, who led the project, had to ask was whether it was possible that the process which ice forms in regions near the poles could contain a detectable record of magnetic pole reversals.

These randomly-spaced reversals have occurred throughout our planet’s history, fuelled by the chaotic motion of the liquid iron dynamo deep in the planet’s core. In banded rock formations and layered sediments, researchers measure the magnetic moment – the magnetic north-south orientations – of the magnetic materials in these to reveal the magnetic moment of the Earth’s magnetic field at that time. The scientists thought such magnetic particles could be found in the dust that gets trapped, along with water ice, in glaciers and ice sheets.

The research team built an experimental setup to simulate ice formation such as that in polar glaciers, where dust particles in the atmosphere may even provide the nuclei around which snowflakes form. They then created artificial snowfall by finely grinding ice made from purified water, adding a bit of magnetic dust, and letting it fall though a very cold column that was exposed to a magnetic field, the latter having an orientation controlled by the scientists. By maintaining very cold temperatures – around 30 degrees Celsius below zero, they found they could generate miniature ‘ice cores’ in which the snow and dust froze solidly into hard ice.

“If the dust is not affected by an external magnetic field, it will settle in random directions which will cancel each other out,” said Aharonson.

“But if a portion of it gets oriented in a particular direction right before the particles freeze in place, the net magnetic moment will be detectible.”

To measure the magnetism of the ‘ice cores’ they had created in the lab, the Weizmann scientists took them to Hebrew University in Jerusalem, to the lab of Professor Ron Shaar, where a sensitive magnetometer installed there is able to measure the very slightest of magnetic moments. The team found a small, but definitely detectible magnetic moment that matched the magnetic fields applied to their ice samples.

“The Earth’s paleo-magnetic history has been studied from the rocky record; reading it in ice cores could reveal additional dimensions, or help assign accurate dates to the other findings in those cores,” said Aharonson.

“Plus we know that the surfaces of Mars and large icy moons like Europa have been exposed to magnetic fields. It would be exciting to look for magnetic field reversals in ice sampled from other bodies in our solar system. We’ve proved it’s possible.”

Aharonson has proposed a research project for a future space mission involving ice core sampling on Mars, and he hopes that this demonstration of the feasibility of measuring such a core will advance the appeal of this proposal.

Share this article

Latest news

Sensing Fat

Sensing Fat

New research from the Weizmann Institute of Science reveals that the nervous system can sense fat tissue and that blocking this ability protects mice from metabolic disorders. Popular belief holds that our senses gather information only about the external world, but...

Food: Friend, Not Foe – New Study Explains Why

Food: Friend, Not Foe – New Study Explains Why

Weizmann Institute of Science researchers have revealed the cellular network behind oral tolerance, the immune mechanism that enables us to eat food safely.  If we have an allergy to peanuts, strawberries or dairy, we are quick to blame our immune systems. But...

MRI Gets a Nano-Sized Upgrade

MRI Gets a Nano-Sized Upgrade

Weizmann Institute of Science researchers have achieved an MRI resolution of one billionth of a metre, paving the way for the most detailed images of individual molecules ever produced. This new development will play a major role in the materials and pharmaceutical...

Beyond Words

Beyond Words

Weizmann Institute researchers have revealed that the melody of spoken English functions as a distinct language, with a vocabulary and rules of syntax.  The findings lay the foundation for an AI that will understand language beyond just words. The AI revolution, which...

All embroidery colours

All embroidery colours

AI-based technology developed in Dr Liat Keren's lab at the Weizmann Institute of Science has shown it enables an unprecedented view of processes in body tissues. Artificial intelligence systems are working magic in many areas of the life sciences – they help decipher...