Claire Nichols, Ph.D.

Education: University of Cambridge, Ph.D., Earth Sciences
Institution: Massachusetts Institute of Technology (laboratory of Benjamin Weiss)

SCOL Project: Determining the Earliest History of Earth’s Ancient Field

The Earth generates its own magnetic field, driven by vigorous mixing of liquid iron within the core. This magnetic field is thought to provide our planet with important protection from a stream of charged particles emitted from the sun, known as the solar wind. If these charged particles enter our atmosphere they cause interactions, changing its composition. Interaction between the solar wind and Earth’s magnetic field can be observed near the poles as spectacular auroras. The solar wind can effectively remove water from planetary surfaces and is thought to be responsible for stripping both Mars and Venus of their surface water. The presence of oceans on Earth is thought to be important for the habitability of our planet, and the preservation of our surface water is thought to be due to protection from our magnetic field.

We are able to track the strength and direction of Earth’s magnetic field through time. As molten rock cools and crystallizes, magnetic minerals within the rock align themselves to the magnetic field at that time. The degree of alignment and direction of alignment of these minerals tells us about the strength and direction of the magnetic field when the rock formed. This record is typically preserved, unless the rock is reheated or altered by reaction with fluids, for example. The direction of the magnetic field recorded by the rock tells us where the rock formed relative to the North and South magnetic poles on Earth. This information is used to reconstruct where the continents and oceans were through time, as they collide and spread apart as a result of plate tectonics. Plate tectonics may play an important role in the origin of life and the diversity of life on Earth today.

We propose a study of 3.7-billion-year-old rocks from the Isua area of southwestern Greenland. Currently the oldest record of the strength and direction of Earth’s magnetic field comes from 3.5-billion-year-old rocks. Reconstructing the magnetic field from such ancient rocks is highly challenging since the rocks have experienced such long and complex histories, including many reheating and deformation events, and are likely to have been altered by interactions with many fluids. Isua provides an exciting opportunity to study such ancient rocks, since these rocks appear to have escaped significant reheating or deformation, making them unique in the ancient rock record.

We will conduct fieldwork in Isua to collect samples. Microscopy will then be used to image the magnetic minerals in the rocks, since their shape, size and distribution will affect how the ancient magnetic field was recorded. We will then use a magnetometer to measure their magnetic properties. Any magnetic minerals that show promising signs of having recorded the magnetic field over 3.7 billion years will then be analyzed to quantify the strength and direction of the magnetic field at this time.