skip to primary navigationskip to content
 

Claire Nichols

Claire Nichols

Research Student 2014-2018

Paleomagnetism

Meteoritics

Planetary Science

Mineral Physics

M06

Email:
Office Phone: 64919

Biography:

2010-2014 BA Natural Sciences, University of Cambridge


I studied a range of subjects at undergraduate level including Physics, Mathematics, Materials Science, Earth Sciences and History and Philosophy of Science.  I specialised in Earth Sciences, which included a 28 day mapping project of the Vredefort Impact Crater, South Africa.

2014-2015 MSci Earth Sciences, University of Cambridge


Involved a three month research project, supervised by Dr Richard Harrison: 'Nanopaleomagnetism of Meteorites: Evidence for a Core Dynamo in the Pallasite Parent Body' as well as lectuered courses including Mineralogy of the Deep Earth, Physics of Mineral Behaviour, Basins, Igneous and Metamorphic Petrology.

Research Interests

Nanopaleomagnetism of Meteorites using X-ray Methods

I use paleomagnetic signals recorded by meteorites to understand more about the dynamics of core dynamos, and the mechanisms by which planets and asteroids form and differentiate. Understanding how and why planets generate magnetic fields is of great importance; our magnetic field provides us with shielding from harmful cosmic rays and allows the Earth to have a stable atmosphere, essential for life as we know it. For a core dynamo to be active, a partially (or entirely) molten metallic core is required in order to initiate vigorous convection. By looking at paleomagnetic signals, we can start to understand the thermal structure and cooling histories of planets and asteroids as they formed during the early stages of our solar system's history. We have already found evidence for a core dynamo 'switching off' as core solidification reaches completion (Bryson et al, Nature, 2015)

I am primarily interested in the paleomagnetic signals recorded by microstructures within meteoritic FeNi metal. Meteoritic metal forms a characteristic 'Widmanstätten' pattern, consisting of a range of microstructure with varying Ni content (~10-50 wt%).  One of these microstructures, known as the 'cloudy zone' consists of nanoscale islands of tetrataenite (50 wt% Ni) in an Fe-rich matrix.  These islands have an ordered structure, and if they grow in the presence of a magnetic field they record that magnetisation and are very resistant to subsequent remagnetisation. We use synchrotron X-rays to image the magnetisation recorded by these individual islands to probe for magnetic field signals locked in by the islands billions of years ago. 

Current Work

So far I have examined the paleomagnetic signals recorded by two pallasites (Brenham and Marjalahti), a group of stony-iron meteorites.  We imaged their cloudy zone using X-ray photoemission electron microscopy (XPEEM) and X-ray magnetic circular dichroism (XMCD) at BESSY II, Helmholtz Zentrum, Berlin.  I have also used the same techniques to examine the relationship between composition and magnetisation for several microstructures found in meteoritic metal (kamacite, tetrataenite rim, cloudy zone, plessite) including a detailed study of the Estherville mesosiderite. 

Another project involves imaging the behaviour of magnetic inclusions within olivine crystals  (from the Semarkona meteorite) under an applied magnetic field. These experiments are carried out using transmission X-ray microscopy (TXM) at the Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley.  The nanoscale inclusions range from single-domain (SD) to pseudo-single-domain (PSD) in size. We are particularly interested in PSD inclusions; their magnetisation has a complex vortex structure which is difficult to interpret in order to extract reliable paleomagnetic signals.  By imaging its behaviour under a range of applied fields, we hope to better understand the paleomagnetic information it can 'store'.  This is important, not just for meteoritic paleomagnetism, but also in order to be able to measure the Earth's early paleomagnetic field during the Archean and Hadean where magnetic grains tend to be larger due to recrystallisation and alteration over geological time.

Research funded by European Research Council, as part of the NanoPaleoMagnetism Group 

Key Publications