Missions, meteorites, and moons

Alpha Regio, a topographic upland ~1,300 km across, imaged using synthetic aperture radar data combined with radar altimetry from the Magellan mission to Venus (~23 x vertical exaggeration) (© NASA JPL)

Planetary geoscience is a vast and growing field, with research that spans from the core to atmosphere of different planetary bodies and through billions of years of history. Rapid advances in technology, particularly remote sensing and autonomous systems, are facilitating expanded exploration of the Solar System (and beyond) and generating exciting datasets. Key areas of investigation include processes such as tectonism, volcanism, and regolith evolution, with a particular focus on volatiles like water, alongside modelling of atmospheric dynamics and habitability. Planetary geoscientists grapple with an interdisciplinary toolkit to understand other planetary bodies, while considering ethical concerns around responsible space governance and planetary protection. Some of these many challenges were discussed during the GeoFutures: Planetary Geoscience Conference held at Burlington House (and via virtual attendance), in November 2024. 

The meeting was part of the Geological Society’s GeoFutures conference series, which launched in 2023 and focuses on the solutions geoscientists provide to global challenges in the 21st century. Thanks to support from the Royal Astronomical Society and Geological Society of America, members of other societies joined the event. There was excellent representation from a range of universities, European and US space agencies, and other organisations, such as UK Research and Innovation (UKRI). Over 200 people registered for the conference, roughly one-third of whom were students.

Solar System tour 

With a focus on mission science; sample collection, curation, and analysis; and remote sensing, all corners of the Solar System were represented at GeoFutures, from micrometeorites to the planets and moons of the inner Solar System, and into and beyond the asteroid belt.  

Luke Daly (University of Glasgow) discussed the role of the Sun’s cosmic rays in irradiating tiny grains across our Solar System, potentially creating a significant reservoir of water on the surface of the Moon and on asteroids following micrometeorite bombardment.

Moving to the gas giants, Mark Burchell (University of Kent) proposed a specialised mission to sample the sub-surface ocean of Saturn’s moon, Enceladus, via a fly-by through the plumes that erupt continually near Enceladus’ south pole. Although Cassini serendipitously sampled these plumes during its 2015 flyby, a dedicated mission could better sample the plumes with more specialised instruments.

Jen Mitchell (University of Minnesota, USA) used compositional and textural analysis of pyroxene in eucrites to infer localised thermal metamorphism on the asteroid 4 Vesta, while Sara Russell (Natural History Museum) reported on the mineral arrays (including phyllosilicates) observed in the pristine regolith sample collected from the asteroid Bennu, which returned to Earth in September 2023 via NASA’s OSIRIS-REx mission. Such a remarkably fragile sample is unlikely to have survived natural entrance into Earth’s atmosphere, implying that our current meteorite collections are biased towards more consolidated materials. 

Thanks to incredible rover imagery, detailed maps of the Martian surface are flourishing

As is often the case at planetary science conferences, research on the planets of the inner Solar System was particularly strong. Thanks to incredible rover imagery, detailed maps of the Martian surface are flourishing, with geological histories being reconstructed from individual rock units. Robert Barnes (Imperial College London) reconstructed ancient episodes of flooding preserved in fluvio-deltaic deposits in the Jezero Crater, while Amelie Roberts (also Imperial College London) detailed wind-formed sedimentary units in Gale Crater that were episodically interrupted by a transient lacustrine environment. 

Closer to home, exciting observations are being made from the Apollo Next Generation Sample Analysis (ANGSA) collection—unopened samples from the Apollo lunar missions, stored for over 50 years with the intention of analysing them once techniques improved. Using X-ray computed tomography, Giulia Magnarini (Natural History Museum) analysed clast sizes within a core sample collected by astronaut Harrison Schmitt during the 1972 Apollo 17 mission—our only sample of an extraterrestrial landslide. Initial results indicate the upper 5 cm of the core is reworked regolith, with further analysis expected to reveal insights into landslide processes on other celestial bodies. 

The ANGSA programme would not have been possible without careful sample storage and curation, highlighting the need for suitable facilities for meteorites or, in the event of sample return, samples from the Moon, Mars, and beyond. Many institutions are bolstering their sample curation facilities, such as the Natural History Museum, London, and the European Space Agency (ESA) through their Vulcan facility in Harwell, Oxfordshire.

Missions to Mercury 

In a detailed overview of our Solar System’s smallest planet and the one closest to the Sun, Jack Wright (ESA and the Open University) summarised current understanding of Mercury. The planet appears to have a large metallic core, thin silicate mantle and crust, and a surface rich in volatiles. Mercury is characterised by ancient volcanic activity, as well as more recent tectonism. Jack highlighted key observations from the 1974 Mariner 10 and 2011 – 2015 MESSENGER missions, while noting unanswered questions that will be investigated by the ESA and Japan Aerospace Exploration Agency (JAXA) mission BepiColombo. Having already conducted several flybys of Mercury, BepiColombo is scheduled to arrive in orbit in 2026 carrying a comprehensive science payload that will enable more detailed study of the planet’s surface structure and composition, interior, magnetosphere, and exosphere. 

Now is the time to start asking the questions we want future missions to answer 

Wright’s talk was comprehensive in placing the upcoming mission science within the context of existing studies of Mercury, while linking in stages from his own research and career – useful for those considering getting involved in future missions. A key message was that now is the time to start asking the questions we want future missions to answer. 

The Apollodorus crater imaged by MESSENGER during its first flyby of Mercury (© NASA/John Hopkins University Applied Physics Laboratory/Carnegie Institute of Washington)

Observing Venus 

Mercury is not the only terrestrial planet at the heart of an upcoming mission. In the early 2030s, ESA, in collaboration with NASA, will launch the EnVision mission to Venus – 40 years after the planet was visited by the Magellan spacecraft.  

Despite being our closest planetary neighbour and of similar size and bulk composition to Earth, Venus could not be more different than our home. Previous missions have given a taste of the vast textural complexity of Venus, with its crust featuring rifts, volcanoes, mountain chains, and the elusive tesserae – highly fractured volcanic plains, believed to comprise some of the oldest parts of the Venusian crust.

We hope to understand how a planet that was initially so similar to Earth became uninhabitable 

However, as Philippa Mason (Imperial College London) explained, little is known for sure. EnVision will orbit Venus and analyse the planet using novel remote sensing techniques aimed at understanding the complex interactions between the atmosphere, tectonics, and planetary interior. EnVision will be equipped with infrared, near-infrared, and ultraviolet spectrometers to enable study of the composition of Venus’ surface and atmosphere, a subsurface radar sounder to probe the top kilometre of the interior, and radio instruments to map the planet’s gravity field and internal structure. EnVision will also utilise synthetic aperture radar to detect crustal features up to 10 m – a huge improvement in resolution that will allow mapping of topography and provide insights into the rock types present. 

EnVision aims to provide a holistic view of Venus, studying the planet in its entirety, from the core, to subsurface and surface, and finally to the upper limits of its atmosphere. From this, we hope to understand how a planet that was initially so similar to Earth became uninhabitable, greatly advancing our understanding of planetary evolution. 

Planetary community 

An overarching theme of GeoFutures was the importance of a planetary science community in the UK and beyond. Katie Joy (University of Manchester) presented on behalf of the UK Cosmochemical Analysis Network (UKCAN), which spans 15 different universities and institutions with labs suitable for planetary sample analysis. While the benefits of a collaborative approach to planetary sample analysis were clear, Joy gave an inauspicious outlook for UKCAN, announcing that the future of funding from the European Union and many universities is uncertain. This may mean that many of the UK’s analytical instruments become outdated within the next decade. Joy is calling on the community for new ideas for obtaining funding to ensure that the UK remains a key player in planetary science. 

While top-down funding may be uncertain, a more bottom-up approach shows much promise for the planetary science community, with citizen science cropping up as a method to aid meteorite recovery. Penny Wozniakiewicz (University of Kent) touched on the success of recovering micrometeorites from urban rooftops, while Luke Daly (University of Glasgow) reported on the UK Fireball Alliance, which aims to record meteors and fireballs using a network of cameras and to recover freshly fallen meteorites across the UK. Their biggest success story is the Winchcombe meteorite, which landed in Gloucestershire in February 2021 and was recovered only 12 hours after it was observed falling through the atmosphere. The UK Fireball Alliance rely on volunteer meteorites enthusiasts to monitor the sky for meteors and fireballs and are open to more people getting involved.

© Marissa Lo

Fresh eyes 

Throughout the meeting, there were several humorous reminders that Earth is also a planet and that much of the science used to understand Earth is wholly applicable to other bodies in our Solar System. During a panel discussion on how planetary scientists can get involved in space missions, an audience member who studies Mars asked if and how they could start researching other planets. The panel keenly supported this, encouraging networking and collaboration, with Philippa Mason sharing her mantra that getting fresh eyes on a project or problem is the best way to drive progress – an encouraging and inspiring message for any planetary scientists (including Earth scientists) interested in taking their research in a new direction. 

Authors

Marissa Lo, Associate Editor, Geoscientist magazine, the Geological Society of London, UK

Thomas Harvey, Science and Funding Officer, the Geological Society of London, UK

Ana Pagu, Planetary Science Education Assistant, the Geological Society of London, UK

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