The Magnetic History of Ice

Glacial ice discoveries by Minerva Center's director might help to understand the history of our solar system

The history of our planet has been written, among other things, in the periodic reversal of its magnetic poles. Scientists around Prof. Oded Aharonson at the Weizmann Institute of Science propose a new means of reading this historic record: in ice. Their findings could lead to a refined probing ice cores and, in the future, might be applied to understanding the magnetic history of other bodies in our solar system, including Mars and Jupiter’s moon Europa.

Investigating a connection between ice and Earth’s magnetic history arose far from the source of the planet’s ice

One of Aharonson's main focus is paleo-magnetism, which is mostly being 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. Aharonson and his student Yuval Grossman searched for small amounts of magnetic materials within ice forms occuring from regions near the poles. They 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. The researchers 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. 

Unique technology for outstanding research

To measure the magnetism of the “ice cores” they had created in the lab, the Weizmann scientists took them to the Hebrew University in Jerusalem, to the lab of Prof. 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: "We found that in a process analogous to detrital remanent magnetism (DRM) that occurs in sedimentary rocks, ice that contains magnetic dust particles can record the planetary field during deposition. Earth's ice deposits, as well as other planets, may exhibit such a signature," says Aharonson.

Successful research at the Minerva Center

Prof. Oded Aharonson is Head of the Helen Kimmel Center for Planetary Science and director of the Minerva Center for Life Under Extreme Planetary Conditions which has been established in 2013. The Center activities focus on important scientific questions in the fields of Planetary Formation and Evolution, Early Life, Origin of Life and Extremophiles. The scientific output can be seen on a very high number of international publications, including those in Science and other high-ranking journals. Many international collaborations with excellent scientists in the respective fields of the Center are being initiated: Besides the Weizmann Institute of Science Israeli participants are the Technion-Israel Institute of Technology and the Hebrew University of Jerusalem. Also German scientists participate from several institutions, including the universities of Tübingen, Göttingen, Duisburg-Essen and Berlin. In addition, the Center is cooperating with DLR in Berlin, DESY, the Thüringen Landessternwarte, and the Max Planck Institute in Bremen.

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