Unravelling the magnetic histories of Earth and other terrestrial objects
Also in “ Scientific meeting”
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Discussion meeting organised by Professor Andy Biggin, Dr James Bryson, Professor Cathy Constable and Professor Wyn Williams.
This meeting will assemble researchers working across vast length and time-scales to understand the multibillion year histories of dynamos operating in the cores of Earth, the Moon, Mars, Mercury and asteroids. Its aim is to lay a platform for recent advances in data, techniques and concepts to tackle major contemporary controversies whose implications stretch far beyond geo- and planetary magnetism.
Programme
The programme, including speaker biographies and abstracts, will be available soon. Please note the programme may be subject to change.
Poster session
There will be a poster session from 5pm on Monday 14 September 2026. If you would like to present a poster, please submit your proposed title, abstract (up to 200 words), author list, and the name of the proposed presenter and institution no later than Friday 28 August 2026.
Attending the event
This event is intended for researchers in relevant fields.
- Free to attend
- Both virtual and in-person attendance is available. Advance registration is essential. Please register via Eventbrite for a ticket
- Lunch is available on both days of the meeting for an optional £25 per day. There are plenty of places to eat nearby if you would prefer purchase food offsite. Participants are welcome to bring their own lunch to the meeting
Please note that scientific meetings hosted by the Royal Society do not necessarily represent a Royal Society position or signify an endorsement of the speakers or content presented.
Enquiries: Scientific Programmes team.
Organisers
Schedule
| 09:00-09:05 |
Welcome by the Royal Society and lead organiser
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| 09:05-09:30 |
Behind the curtain: revealing the rock magnetic behaviour of Earth and planetary materials using X-ray magnetic imaging
Paleomagnetism – the study of past magnetic fields on Earth and beyond – has shaped our understanding of Earth's dynamic history and is a powerful tool to investigate the structure and evolution of the early solar system. The basis of paleomagnetism is the principle that stable magnetisation in rocks is carried by small (<100 nm) uniformly magnetised ‘single-domain’ grains. However, recent advances show that most natural remanence carriers are, in fact, grains of intermediate size (100s–1000s of nm) that adopt complex, non-uniform remanent states known as ‘vortex’ states. Major breakthroughs in high-resolution X-ray magnetic imaging mean we can now investigate these phenomena in unprecedented detail. This talk will describe recent applications of 2D X-ray imaging and 3D X-ray magnetic vector tomography to terrestrial and extraterrestrial materials in addition to providing an outlook on how these methods are poised to revolutionise the study of rock magnetism over the coming decade. As we enter the era of in-situ 3D magnetic imaging at simultaneous high temperature and in-field conditions, the parameter space accessible to experimental observation promises to match precisely that which can be accessed through micromagnetic simulation. The resulting insights will guide the development of new micromagnetic models, driving progress in cutting-edge research and providing renewed confidence in the methods we use to extract and interpret paleomagnetic data from even the most challenging samples. 
Professor Richard HarrisonUniversity of Cambridge, UK
Professor Richard HarrisonUniversity of Cambridge, UK Richard Harrison is Professor of Earth and Planetary Materials at the University of Cambridge. He leads the NanoPaleoMagnetism research group that was established in 2013 via the award of an ERC Advanced Grant. Harrison employs an innovative combination of experimental and computational techniques to study magnetism in natural and synthetic materials, with particular emphasis on nanoscale processes. |
| 09:30-09:45 |
Discussion
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| 09:45-10:10 |
The magnetic record of CV chondrites: parent body dynamo or solar nebula field?
CV chondrites are aqueously altered meteorites that experienced various degrees of thermal metamorphism. Paleomagnetic studies of bulk CV chondrites have disproportionately focused on Allende, with >30 published studies against two for other CV chondrites (Kaba and Vigarano). Allende carries a characteristic remanent magnetization, interpreted as the record of an ancient field, but no consensus has been reached regarding its nature and origin: chemical remanent magnetization (CRM) reflecting the solar nebula field, thermoremanent magnetization (TRM) reflecting a parent body dynamo field, or shock remanent magnetization reflecting one of those fields. Solving this conundrum would either place important constraints on the solar nebula field intensity, or support the existence of partially differentiated planetesimals, ie, with a differentiated interior overlaid by a chondritic shell (birth place of the CV chondrites). To do so, we set aside Allende and turn to other members of the CV chondrite group. I will present the results of a series of rock magnetic and paleomagnetic measurements conducted on 30 CV chondrites: hysteresis and susceptibility at room and high temperature, AF and thermal demagnetization, Thellier-Thellier experiments. I will focus on thermal demagnetization data to try deciphering the nature of the NRM: if CV chondrites carry a (partial) TRM, their unblocking temperatures should correlate with their degree of metamorphism, while there should be no correlation between those parameters if the NRM is in fact a CRM. Preliminary data seem to favor the hypothesis that CV chondrites recorded a pTRM, which we argue is most compatible with the record of a dynamo field, supporting the idea that the CV chondrite parent body was partially differentiated. 
Dr Clara MaurelCEREGE - CNRS, France
Dr Clara MaurelCEREGE - CNRS, France Clara is a CNRS researcher at the Centre de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE) in Aix-en-Provence, France. She is interested in how planetary bodies formed and evolved in the early times of the solar system. Specifically, she investigates the magnetic and structural properties of meteorites to understand how planetesimals—the building blocks of the planets—accreted, differentiated, and generated magnetic fields. She was trained as an aerospace engineer at ISAE-Supaéro and obtained her PhD in Planetary Sciences at MIT under the supervision of Professor Benjamin Weiss in the department of Earth, Atmospheric and Planetary Sciences (EAPS). She then joined the CEREGE as a MSC postdoctoral fellow and then a CNES Postdoctoral Fellow. |
| 10:10-10:25 |
Discussion
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| 10:25-10:50 |
Break
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| 10:50-11:15 |
Quantum diamond microscopy
Dr Lennart de GrootUtrecht University, The Netherlands
Dr Lennart de GrootUtrecht University, The Netherlands Lennart de Groot is Associate Professor at the Paleomagnetic Laboratory, Fort Hoofddijk, Utrecht University. His research centres on reconstructing Earth's short-term magnetic field behaviour by developing innovative techniques, including the use of quantum diamond microscopy to access micro- to nanoscale magnetic recording in rocks. His work has contributed to improving the recovery of robust paleomagnetic signals from challenging materials and to refining understanding of field instability in the Southern Hemisphere, including the evolution of the South Atlantic Anomaly. He holds an ERC Consolidator Grant and previously received an ERC Starting Grant as well as VENI and VIDI awards from the Dutch Research Council. He is a recipient of the AGU William Gilbert Award and the Vening Meinesz Prize. He leads an internationally active research group. Beyond his research, he established a science theatre initiative, now in its sixth season, that trains PhD candidates in communicating science on stage. |
| 11:15-11:30 |
Discussion
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| 11:30-11:55 |
Assessing high-resolution Quaternary geomagnetic field behaviour: is there a geomagnetism-climate relationship?
Relationships between geomagnetic field and climate variability have been proposed, controversially, on various timescales for more than 60 years. Reported relationships on orbital timescales usually prove to be due to climatic contamination of sedimentary magnetic properties that are difficult to remove from the normalized remanence records used to estimate relative geomagnetic palaeointensity. Any new claims of such relationships are, thus, usually greeted by scepticism. High-resolution comparison of geomagnetic field behaviour and climate is only possible through the last glacial cycle in which climate records typically have multi-decadal to millennial resolution; palaeomagnetic records generally have lower resolution than this. Speleothems provide excellent paleomagnetic archives with magnetizations locked in rapidly by carbonate cementation and high-resolution chronologies provided by precise radiometric dating. Ice core cosmogenic isotope records provide further temporally well resolved evidence for dipolar geomagnetic field changes. Results from the most highly resolved sediment and ice core records indicate frequent dipole field strength changes, many of which are associated with directional geomagnetic excursions, which are well recorded by speleothems. The temporal precision of these records enables geomagnetic-climatic comparison, including from the same archive (e.g., ice core or speleothem), to assess potential links. Such records are explored here to seek a balanced assessment of inter-relationships between geomagnetic field and climate changes based on existing and new evidence. 
Professor Andrew RobertsAustralian National University, Australia
Professor Andrew RobertsAustralian National University, Australia Andrew Roberts is a Professor in the Research School of Earth Sciences, Australian National University. He works on palaeomagnetic, rock magnetic, and environmental magnetic studies of climate and environmental change, geomagnetic field behaviour, geochronology, tectonics, and biomagnetism. He has co-authored >300 papers in peer-reviewed scientific journals. He is a Fellow of the American Geophysical Union (AGU) and an Honorary Fellow of the Royal Society of New Zealand. He has been awarded the Leverhulme Prize (UK), Axford Medal (Asia Oceania Geosciences Society), Mawson Medal (Australian Academy of Science), AGU Edward Bullard Lectureship, and was appointed as an Excellent Researcher at the Geological Survey of Japan. He has served for 15 years in university senior management roles and on scientific advisory committees in the UK, USA, China, Taiwan, Japan, France, Germany, Italy, The Netherlands, Norway, Australia, and New Zealand. His book, Mineral Magnetism, was published in late 2025 by Cambridge University Press. |
| 11:55-12:10 |
Discussion
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| 13:10-13:35 |
Paleomagnetic records from Sample Return Missions
Paleomagnetic investigations of meteorites have a long history, but they are often complicated by uncertainties in sample handling. The terrestrial curatorial histories of many specimens are poorly documented, and until recently the use of hand magnets to assess whether a rock was of extraterrestrial origin was common practice, potentially overprinting pre-terrestrial magnetic signals. An alternative approach is the study of well-curated material collected directly by space missions and returned to Earth. In addition to the Apollo and other lunar sample return programs, several missions have retrieved samples from small bodies. NASA’s Stardust mission collected cometary dust from comet Wild 2 in aerogel and returned it in 2005. The Japanese Space Agency (JAXA) has conducted two successful asteroid sample–return missions: Hayabusa, which returned grains from S type asteroid Itokawa in 2010, and Hayabusa2, which delivered material from C type asteroid Ryugu in 2020. In 2023, NASA’s OSIRIS REx mission returned 121 g of material from B type asteroid Bennu, the largest mass of asteroid sample yet obtained. Among these later missions, the Hayabusa2 samples have received the most extensive paleomagnetic study, although results remain contradictory and may reflect magnetic contamination introduced by the spacecraft. Looking forward, new opportunities for extraterrestrial paleomagnetism studies will arise from the planned return of samples from Phobos in 2031 by JAXA’s MMX mission, from the lunar south polar region via NASA’s Artemis program, and hopefully ultimately from sedimentary and igneous materials collected in Jezero crater as part of the NASA–ESA Mars Sample Return campaign. 
Professor Sara RussellNatural History Museum, UK
Professor Sara RussellNatural History Museum, UK Sara Russell is a Merit Researcher at the Natural History Museum, where she leads the Origin and Evolution of Planets theme. She is also a visiting professor of Planetary Sciences at Imperial College. Her research uses meteorites and material brought to Earth by space missions to investigate the formation of the Solar System and the Earth’s Moon. She is involved in several space missions, most recently being Deputy Mission sample scientist for NASA’s OSIRIS-REx mission to asteroid Bennu, and is a member of the Science Board for JAXA’s MMX mission that will visit Mars’ moon Phobos and return a sample to Earth. |
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| 13:35-13:50 |
Discussion
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| 13:50-14:15 |
Particles to Planets: Closing the gap between palaeomagnetic theory and experiments.
Palaeomagnetic techniques enable us to track tectonic plates, gain insights into Earth’s deep interior, and record changes in Earth’s environment over geologic time. Despite the many successful applications of experimental palaeomagnetism, there has been a significant gap in our theoretical understanding for the past eighty years. We only understand the behaviour of a tiny fraction of the particles that carry the magnetization in natural materials - our theory does not match reality. As a consequence, there may be significant biases in our understanding of planetary scale geological processes. We present a new approach that models the magnetic behaviour of thousands of tiny particles found in geological samples, to understand how these tiny signals influence our interpretation of planetary scale processes. We achieve this by producing micromagnetic simulations of particles with a variety of sizes, shapes, and mineral compositions to capture the diversity seen in real rock samples. By combining these models in different ways, we can simulate a palaeomagnetic experiment that accounts for the geological history that a sample has experienced. A wide range of experiments can be simulated, giving us a highly adaptable model that is already being used for a variety of applications - from detecting archaeological forgeries to understanding the source of lunar magnetic anomalies. This new approach enables us to close the gap between theory and experiment, taking us from particles to planets. 
Dr Brendan CychUniversity of Liverpool, UK
Dr Brendan CychUniversity of Liverpool, UK Dr Brendan Cych is a postdoctoral researcher at Géosciences Montpellier (Université de Montpellier). He received a master's in Earth science from the University of Oxford, and a PhD in geology from the University of California, San Diego, and previously held a postdoctoral research associate position at the University of Liverpool. Brendan’s research focuses on understanding how tiny particles in rocks can record the history of Earth’s magnetic field over geological timescales (and how they sometimes can’t). His work combines new computational, experimental and analytical techniques to develop a comprehensive theory that uses these microscopic magnetic particles to explain planetary scale processes. |
| 14:15-14:30 |
Discussion
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| 14:30-15:00 |
Break
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| 15:00-15:25 |
Dynamo generation in exoplanets
Planetary magnetic fields prevent high energy particles reaching the surfaces, making the planets more habitable. For Earth, the magnetic field is generated within the liquid outer core in the presence of the solid inner core, but this mechanism may not be applicable to many Earth-like exoplanets as some of them may have entirely liquid or solid iron cores. An alternative mechanism is dynamo production in their magma oceans (MOs). A surface magma ocean could be present on a highly irradiated planet from the host star or a deep magma ocean may exist at the core-mantle boundary. For this MO-driven dynamo to work, the magma has to have a high electrical conductivity, but these values have not been fully constrained to date. To investigate the likelihood of MO-driven dynamos, we estimate the electrical conductivity of MO-analogue materials by conducting laser-driven shock experiments, density functional theory molecular dynamics simulations (DFT-MD), and thermal and magnetic field evolution modeling of Earth and super-Earths. We find that super-Earths larger than 3–6 Earth masses likely produce BMO-driven dynamos lasting a few billion years, which may be observable in the future. We also extend our discussion to potential interactions between core and MO-driven dynamos as well as to MO-driven dynamos in mini-Neptunes. 
Professor Miki NakajimaUniversity of Rochester, US
Professor Miki NakajimaUniversity of Rochester, US Miki Nakajima is an Associate Professor in the Department of Earth and Environmental Sciences at the University of Rochester. Her expertise includes planetary impacts and the formation and evolution of planets, studied using numerical simulations and laser-driven shock experiments. She received her BSc and MSc degrees from the Tokyo Institute of Technology and her PhD from the California Institute of Technology. Before moving to Rochester, she was a postdoctoral fellow in the Department of Terrestrial Magnetism at the Carnegie Institution for Science. She received a National Science Foundation CAREER Award in 2023. |
| 15:25-15:40 |
Discussion
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| 15:40-16:05 |
Non-dipole structures in the geomagnetic field
Professor Ricardo TrindadeUniversity of São Paulo, Brazil
Professor Ricardo TrindadeUniversity of São Paulo, Brazil Trindade is a Full Professor at the University of São Paulo, where he was Vice-Director and Director of the Institute of Astronomy, Geophysics and Atmospheric Sciences. He earned a PhD in Geophysics from the University of São Paulo (1999). His research focuses on rock magnetism, paleomagnetism, and archaeomagnetism, addressing paleoenvironmental changes across Earth’s history, including the Neoproterozoic–Cambrian transition, Phanerozoic biotic crises, and recent geomagnetic field behavior in the South Atlantic Magnetic Anomaly. More recently, he focused on the application of magnetic microscopy techniques to paleomagnetism and paleointensity studies, advancing high-resolution characterization of remanence carriers and improving the reliability of geomagnetic field reconstructions. He has authored over 200 peer-reviewed papers, leads major national and international projects, has supervised more than 40 graduate students and postdoctoral fellows, and is a member of TWAS and the Brazilian Academy of Sciences. |
| 16:05-16:20 |
Discussion
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| 16:20-17:00 |
Poster flash talks
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| 09:00-09:25 |
Planetary magnetic fields
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| 09:25-09:40 |
Discussion
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| 09:40-10:05 |
Lunar magnetism: insights into dynamo evolution and impact processes
The history of the lunar magnetic field provides insight into the Moon’s thermochemical and geodynamical evolution, core energetics, and trapping of water and 3He resources in the regolith. Crustal magnetic anomalies provide evidence for an active lunar dynamo prior to ~3.9 billion years ago (Ga), whereas paleomagnetic studies of Apollo and Chang’e samples aged between ~4.2 Ga and ~1.5 Ga reveal stable magnetizations that are also widely interpreted as dynamo records. However, some coeval lunar rocks appear unmagnetized, raising the possibility that the dynamo was intermittently intense or that the origin of stable remanences in samples is being misinterpreted. We present results from laboratory pressure, isothermal, and viscous remanent magnetization acquisition experiments that demonstrate that stable, high coercivity magnetizations observed in lunar mare basalts are unlikely to be related to shock remanent magnetization acquired from transient impact plasma fields or from exposure to spacecraft fields during sample return to Earth. We also discuss quantum diamond microscope mapping and coercivity analyses that demonstrate that many, but not all, FeNi grains within mare basalts can reliably regain high coercivity magnetization records. Due to intra-sample heterogeneity, <1 mm specimens may lack the high coercivity grains required to retrieve robust paleointensity records; we therefore advocate for collecting larger samples during future lunar exploration. Together, our results support an intermittently intense dynamo origin for the stable remanence carried by high-coercivity grains in lunar rocks, reconcile paleointensity variability among coeval rocks without invoking pervasive impact remagnetization, and inform future sampling strategies. 
Professor Sonia TikooStanford University, US
Professor Sonia TikooStanford University, US Dr Sonia Tikoo is an Assistant Professor of Geophysics and, by courtesy, of Earth and Planetary Sciences at Stanford University. She serves as the Principal Investigator of the Stanford Paleomagnetism and Planetary Magnetism Laboratory. She uses paleomagnetism and fundamental rock magnetism as tools to probe the magnetic history of the Moon, impact cratering processes, and other problems in the planetary sciences. Tikoo received her PhD in Planetary Sciences from MIT in 2014. |
| 10:05-10:20 |
Discussion
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| 10:20-10:50 |
Break
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| 10:50-11:15 |
A promising novel recorder of Earth’s ancient magnetic field: fossil micrometeorites as paleomagnetic archives
The paleomagnetic record from sedimentary rocks is often ambiguous, limiting the recovery of reliable paleomagnetic data, particularly when compared to paleomagnetic data obtained from igneous rocks. I will introduce a novel, unexplored recorder of Earth’s magnetic field: fossil micrometeorites. Micrometeorites (MM) are small cosmic particles (50 μm-2mm) that make up a substantial part of the ~40,000 tons of extraterrestrial material delivered to Earth each year. Many MMs melt during atmospheric entry at altitudes of 80-90 km, transforming into cosmic spherules (CS). During this process, particles oxidise and form new minerals, particularly wüstite and magnetite, which record thermoremanent magnetisations upon subsequent cooling. CS are strongly magnetic and can be extracted from sedimentary rocks. Diagnostic features such as metal beads and vesicles inside some CS allow the reconstruction of their flight trajectory, which can be combined with their magnetisations to reconstruct the polarity of Earth’s magnetic field. While modern CS from Antarctica are already known to be robust recorders of the geomagnetic field, their deep-time counterparts remain almost entirely unexplored. I will present the first results of a paleomagnetic study of anthropogenic magnetite spherules that resemble iron-type (I-type) CS, as well as several Paleozoic I-type CS. These 50-300 μm spherules are measurable with standard paleomagnetic tools and, together with flight trajectories obtained using NanoCT scanning, are capable of opening a new window on the ancient geomagnetic field. 
Dr Annique van der BoonUniversity of Oslo, Norway
Dr Annique van der BoonUniversity of Oslo, Norway Annique van der Boon is a paleomagnetist at the University of Oslo (Norway), and principal investigator of the PANDA project (Norwegian Research Council Young Research Talent). Her research has focused on enigmatic intervals of Earth’s history (notably the Devonian) and more recently on developing and validating novel recorders of Earth's magnetic field. She is intrigued by the expression of natural phenomena as recorded by rocks, and what rocks can tell us about the history of our planet. Annique is a firm believer that fieldwork and science communication are essential components of Earth science and is committed to building collegial, collaborative and inclusive research environments that enable ambitious, curiosity-driven science. |
| 11:15-11:30 |
Discussion
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| 11:30-11:55 |
Dynamics or polarity reversals and excursions from strong-field spherical dynamos
Earth’s magnetic field is dominated by an axial dipole component that is presently closely aligned with the geographic poles. On timescales of tens to hundreds of thousands of years the magnetic poles can wander far from the geographic axis and even reverse polarity. These rare and erratic events, polarity excursions and reversals respectively, contain potentially crucial insights into the operation of the geodynamo that maintains the main magnetic field in Earth’s liquid iron core, which can be probed with numerical simulations. Indeed, a major success of early geodynamo simulations was the natural emergence of dipole-dominated fields and occasional reversals. However, it is now known that many simulated reversals arise due to enhancement of fluid inertia and reduction in magnetic/kinetic energy compared to Earth’s core. Recently, several studies have obtained polarity reversals in the so-called “strong-field” regime where the magnetic/kinetic energy ratio exceeds unity and inertial effects are suppressed relative to magnetic forces, which is more relevant to the geodynamo. In this talk I present an analysis of the reversal mechanism in strong-field simulations within the framework of mean-field dynamo theory. I link changes in the internal state of the dynamo to properties of the core surface flow that drive changes in the dipole moment and discuss potential relationships between polarity reversals and excursions. 
Professor Christopher DaviesUniversity of Leeds, UK
Professor Christopher DaviesUniversity of Leeds, UK My research advances our understanding of the dynamics and evolution of Earth’s deep interior. I am particularly interested in the generation of Earth’s magnetic field by fluid motion in its electrically conducting outer core and the manner in which this process is controlled by the overlying mantle and the solid inner core. To this end, I design theoretical and numerical models that describe the thermodynamic evolution of the core–mantle system and the fluid dynamics of magnetic field generation. Using these techniques, my group works on a number of outstanding challenges in deep Earth geophysics, including constraining Earth’s heat budget over geological time, the growth history and dynamics of the solid inner core, the origin of anomalous regions in the fluid outer core, and thermo-chemical coupling between the core and mantle and its signature in geomagnetic field observations. |
| 11:55-12:10 |
Discussion
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| 13:10-13:35 |
Coevolution of the core, magnetosphere, and life
Professor John TardunoUniversity of Rochester, US
Professor John TardunoUniversity of Rochester, US John is a Guggenheim Fellow, as well as Fellow of the American Geophysical Union (AGU), and American Association for the Advancement of Science (AAAS). He is recipient of the Price Medal of the Royal Astronomical Society (RAS), and Petrus Peregrinus Medal of the European Geosciences Union (EGU). John’s research centers on detecting the past geomagnetic field to learn about the evolution of Earth’s surface and deep interior. In his publications, he asserts that the geomagnetic field is essential for the development and sustainability of a habitable planet. |
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| 13:35-13:50 |
Discussion
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| 13:50-14:15 |
Earth’s paleomagnetic field through time: From the time-averaged dipole to geomagnetic extremes
The Earth’s magnetic field varies across a wide range of spatial and temporal scales. Although it is predominantly dipolar for most of its history, it also undergoes extreme transitions characterised by significant changes in field strength and direction. Reversals are global polarity changes during which the field weakens and subsequently re-establishes itself with an opposite, stable dipolar configuration. Excursions, on the other hand, may range from global events involving brief polarity changes to more regionally confined and less pronounced events. Compilations of paleomagnetic data from sediments, archaeological artefacts, and volcanic records, spanning different time intervals from the Holocene to hundreds of millions of years, enable global reconstructions of the geomagnetic field. These models range from time-dependent over the past 100 ka to time-averages representing selected periods extending back 100 Ma. Although the number of available records continues to increase, sensitivity to the core-mantle boundary field remains, in general, biased toward the Northern Hemisphere across all timescales, reflecting the uneven spatial distribution of the data. Recent models employ sophisticated modelling techniques to better account for data noise and to provide model uncertainty estimates. I will present a series of geomagnetic field reconstructions spanning Holocene timescales to multi-million-year averages, and excursions and reversals. The models are analysed in terms of the Gauss coefficients, and field features at both the Earth’s surface and the core-mantle boundary. 
Dr Sanja PanovskaGFZ Helmholtz Centre for Geosciences, Germany
Dr Sanja PanovskaGFZ Helmholtz Centre for Geosciences, Germany Sanja Panovska is a Group Leader at the GFZ Helmholtz Centre for Geosciences, Section Geomagnetism in Potsdam, Germany. She received her PhD from ETH Zürich and held a postdoctoral position at UCSD, Scripps Institution of Oceanography, before joining GFZ. Her work focuses on global reconstructions of the geomagnetic field on long-term timescales, encompassing data compilation and analysis, modelling, and implications. A special focus is on the most extreme events on these timescales, geomagnetic excursions and reversals, and understanding their core dynamics, field morphologies, and shared characteristics. This research is funded by the ERC Consolidator Grant EXCURSION, awarded in 2024, and is being undertaken by her research group. |
| 14:15-14:30 |
Discussion
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| 14:30-15:00 |
Break
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| 15:00-15:25 |
Earth’s early magnetic shield: constraints on Precambrian field strength and atmospheric loss
Earth’s magnetic field is often argued to play a key role in our planet’s apparently unique habitability. The magnetosphere influences atmospheric retention and shields the surface from harmful radiation. However, the behaviour of the geodynamo prior to 2 billion years (Ga) ago remains incompletely understood. This is due to a host of challenges with the interpretation and acquisition of whole rock paleointensity data. There are significant uncertainties associated with recovering paleointensities from chemical remanent magnetizations and accurately determining the time of remanence acquisition. Additionally, it is often difficult to reliably determine paleolatitudes and to establish likely reversal rates and secular variation for the early geodynamo, making characterization of precise virtual dipole moments challenging. Here we reassess Precambrian paleointensity constraints by explicitly incorporating these uncertainties into estimates of ancient magnetic field strength and virtual dipole moment. Uncertainties associated with chemical remanence acquisition, paleolatitude, and geomagnetic variability are treated probabilistically to evaluate how statistically similar the ancient field may have been to the present-day geodynamo. These comparisons are key to explore constraints on the operation of the pre-inner-core geodynamo and its relationship to major transitions in Earth history, including atmospheric oxygenation and the emergence of habitable surface environments. Using these revised paleointensity constraints, we further estimate likely subsolar magnetopause standoff distances through deep time and explore first-order implications for hydrogen escape under different magnetic shielding scenarios. Together, these results provide a quantitative framework to link paleomagnetic observations, core evolution, atmospheric escape, and the long-term evolution of Earth’s habitability. 
Dr Claire NicholsUniversity of Oxford, UK
Dr Claire NicholsUniversity of Oxford, UK
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| 15:25-15:40 |
Discussion
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| 15:40-16:05 |
Magnetism of the Chang’e returned samples: From magnetic properties to lunar magnetic field evolution
Evolution of the lunar magnetic field provides key constraints on the Moon’s internal structure and dynamical processes. Magnetic studies of samples returned by the Apollo missions have established the foundational framework for our understanding of lunar magnetic field evolution. However, these samples were all collected from low-latitude regions on the lunar near side, and most basalt records are older than 3 billion years, leaving large uncertainties regarding the duration and operating mechanisms of the lunar dynamo. The Chang’e-5 and Chang’e-6 missions returned lunar regolith samples from the Moon’s mid-latitudes and far side, expanding the range of sampled regions and geological settings. In particular, basalts with ages of ~2.8 and ~2.0 Ga provide unique opportunities to investigate the magnetic field during the poorly constrained middle stages of lunar evolution. Paleomagnetic results from these samples suggest that the lunar magnetic field may have experienced a rebound around 2.8 Ga and that a weak magnetic field still persisted at ~2.0 Ga. These observations imply that the lunar dynamo, after an early rapid decline, may have been reactivated and persisted into the middle stage of the Moon’s evolution. In addition, magnetic properties of some Chang’e samples show notable differences from those of the Apollo samples, providing new insights into the magnetic mineralogy and recording capability of lunar materials. Magnetic results of the Chang’e samples will expand our understanding of the magnetic properties of lunar materials and the spatiotemporal evolution of the lunar magnetic field. 
Dr Shuhui CaiInstitute of Geology and Geophysics, Chinese Academy of Sciences, China
Dr Shuhui CaiInstitute of Geology and Geophysics, Chinese Academy of Sciences, China Dr Shuhui Cai is a professor at the Institute of Geology and Geophysics, Chinese Academy of Sciences. She studies the evolution of the Earth’s and Moon’s magnetic fields and their underlying dynamo processes. Her research integrates archaeomagnetism, paleointensity reconstruction, and planetary magnetism, with a focus on the long-term evolution of the geomagnetic field and the lunar magnetic field. She constructed a Holocene geomagnetic reference curve and a regional field model for East Asia, identifying episodes of abrupt geomagnetic variation. She further revealed a geomagnetic low anomaly in Southeast Asia and proposed that magnetic flux expulsion at the core–mantle boundary may be widespread at low latitudes, providing new constraints on core–mantle boundary structure and geodynamo simulations. In addition, she obtained key evidence for the operational state of the lunar dynamo during the Moon’s middle evolutionary stage. Her results suggest that after an early rapid decline, the lunar magnetic field may have rebounded around 2.8 Ga, and that a weak magnetic field still existed at ~2.0 Ga, thereby revising the prevailing framework of lunar magnetic field evolution. Her work has been published in leading journals, including Nature, Science Advances, and Proceedings of the National Academy of Sciences. Dr Cai has served as Principal Investigator and key contributor on multiple projects funded by the National Natural Science Foundation of China and the Chinese Academy of Sciences (CAS). She received the Fu Chengyi Young Scientist Award from the Chinese Geophysical Society in 2019. In 2020, she was named a core member of the Ministry of Science and Technology’s Innovative Talent Promotion Program in the key area of “Geomagnetic Field Evolution and Its Applications.” In 2022, she was a key contributor to the team awarded the CAS Prize for Outstanding Scientific and Technological Achievement for research on the biological effects of geomagnetic field variations. More recently, she was selected for the “Phoenix Program” Outstanding Young Talent Award (Beijing, 2024), received the inaugural Tengchong Young Scientist Award (2025), and was honoured with the Tan Kah Kee Young Scientist Award (2026). She currently serves on the editorial working group of National Science Review and as a Youth Editorial Board Member of Earth and Planetary Physics. |
| 16:05-16:20 |
Discussion
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| 16:20-16:45 |
Apparent polar wander paths and their errors
Earth is the only terrestrial planet with a long-lived dynamo-driven magnetic field and the ancient magnetic field recorded in surface rocks is the only quantitative way of reconstructing continents before the Cretaceous. Paleomagnetic results can be expressed in terms of paleopoles that are calculated using the geocentric axial dipole field model. Those paleopoles can in turn be used to construct apparent polar wander paths (APWPs), which record the motion of the polar axis relative to a fixed continent. The two most common methods for generating APWPs are the running mean and the spherical smoothing spline methods. Here we extend the spherical smoothing spline approach for APWP construction by propagating age, directional, and flattening-correction uncertainties through a Monte Carlo framework. Uncertainty in the spline paths was quantified by sampling these error sources from their respective distributions. For each synthetic pseudo-pole realization, we computed a smooth spline path where we also let the smoothing parameter vary randomly, thereby propagating uncertainty associated with spline regularization. Spline paths were evaluated at 10 Myr intervals, and the ensemble was used to derive mean spline paths with 95% confidence regions for the major continental blocks for the past 540 Myrs and a global APWP since the assembly of Pangea at 320 Ma. The spherical spline method is superior to the running mean technique, particularly in intervals with poor data coverage or where pole ages are unevenly distributed. 
Professor Trond Helge TorsvikUniversity of Oslo, Norway
Professor Trond Helge TorsvikUniversity of Oslo, Norway Professor in Geodynamics at the University of Oslo and founding Director of two Norwegian Centers of Excellence, the Center for Earth Evolution and Dynamics (CEED: 2013-2023) and the Center for Planetary Habitability (PHAB: 2023-2033). Torsvik is an expert in paleomagnetism, Earth History, paleogeography, plate tectonics and mantle dynamics. He is a member of the Norwegian Academy and awarded the prestigious Wollaston Medal (Geological Society London) in 2024, the Fridjof Nansen Medal (Norwegian Academy of Science and Letters) in 2017, and the Arthur Holmes Medal (European Union of Geosciences) in 2016 among various other awards and prizes. He has written more than 250 articles and one book - Earth History and Palaeogeography (Cambridge University Press, 2017) - which received the PROSE Award in 2018 for best Earth Sciences book. |
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