Our first Departmental Seminar of term is this Thursday 17 October at 12.15 in G41 and will be given by Dr. Martin Suttle (Open University). Martin’s talk will be entitled:

“Phaethon’s Perihelion Puzzle: How Rapid Heating and Volatile Gas Interactions Drive Comet-Like Behaviour in Near-Sun Asteroids”

Martin is a planetary scientist who specialises in applying geochemical analysis and experimental petrology to understand the origin, impact, and potential applications of extraterrestrial material. He has recently been working on new micrometeorite-based palaeoclimate proxies and the origin of Earth’s oceans, so has research interests that overlap with many in the Department. I want to emphasise that all students and staff are welcome at these seminars, and it would be great to see as many of you there as can make it!

If you can’t make it to G41, please contact f.richards19@imperial.ac.uk to be sent a Teams link.

Please also get in touch (f.richards19@imperial.ac.uk) if you would like to meet Martin on Thursday afternoon and/or if you would like to join us for dinner.

Abstract

The near-Sun asteroid (3200) Phaethon exhibits both asteroid and comet-like characteristics, presenting a unique case study for investigating solar radiant heating as an active geological process on solar system small bodies. Despite its predominantly rocky composition and repeated close approaches to the Sun – resulting in surface temperatures exceeding 730°C – Phaethon continues to display cometary activity. Typically, we expect bodies subject to solar radiant heating to either emit gas and shed dust, exposing fresh material with each cycle, or form a barren crust that protects the volatile-rich interior, leading to an absence of further activity. However, Phaethon appears to be an exception, exhibiting faint activity, likely driven by gas or very fine dust, but apparently without significant surface renewal.

To understand this anomaly, we conducted experiments simulating intense solar heating cycles on analogue materials (CM chondrite chips) representing Phaethon’s surface composition. Our findings indicate that phyllosilicate and carbonate decomposition cannot explain the activity due to their rapid and irreversible gas release. Emission of Na gas also appears limited a minor role. By contrast, the reversible decomposition of Fe-sulphides, combined with low permeability, enables an unexpected gradual gas release behaviour, that occurs over multiple heating cycles. Based on this data, we predict the regolith composition and gas emission profile of Phaethon. Our study offers a framework for interpreting data from the upcoming DESTINY+ space mission. Will the scientific instrumentation on DESTINY+ be able to test our predictions?

About the speaker

Dr Martin D. Suttle is a Lecturer in Planetary Science at the Open University, within the School of Physical Sciences. He holds a PhD in Planetary Science from Imperial College London and previously worked as a post-doctoral researcher at the University of Pisa and the Natural History Museum, London. Martin’s work specialises in the microanalysis of extraterrestrial materials (meteorites and micrometeorites) using geochemical and isotopic methods, supported by modelling or experimental petrology. Current research interests include: experimental petrology to support space mission science, investigating the role of cosmic dust as a supplier of nutrients to the early Earth, developing the use of fossilized micrometeorites as a palaeoclimate proxy for reconstructing Earth’s atmospheric composition in the past and the isotopic analysis of water in meteorites to determine the origin of Earth’s oceans.