Earth’s geological carbon cycle is central to both climate and life. It is generally considered to act as a “thermostat,” regulating climate and preventing global mean temperatures from fluctuating wildly. The textbook model of this regulation involves variations in solid Earth degassing rates, leading to changes in atmospheric CO₂ concentrations, surface temperature, and precipitation; in turn, these modulate the rate of alkalinity production via continental silicate weathering, which changes the rate of carbonate mineral formation, thereby rebalancing the carbon cycle. The articles in this issue highlight many alternative or additional mechanisms that may be equally or more important in regulating Earth’s carbon cycle. This issue highlights advances in our understanding of the regulation of the long-term carbon cycle, but also emphasizes the large uncertainties that still remain for both the modern day and in the past: what is the rate of carbon degassing? What are the relative roles of continental and seafloor weathering in regulating the carbon cycle? What fraction of the alkalinity added to the ocean plays a role in the carbon cycle? What role does organic carbon play in the carbon cycle? We are still far from having a complete understanding of the fundamental controls of Earth’s life-support system, but we clearly need to move beyond the textbook model.

• How Well Do We Understand the Geological Carbon Cycle?
• Igneous and Metamorphic CO₂ Sources: How Large and How Variable?
• Continental Weathering as Climate Stabilizer
• The Role of Seawater Interaction with Oceanic Floor in the Carbon Cycle
• The Fate of Ocean Alkalinity: Carbonate Formation and Reverse Weathering Reactions
• Burned or Buried: What Controls the Long-Term Preservation of Organic Carbon?

Excalibur Mineral Corporation

MINERAL PHYSICS APPLIED TO EARTH AND PLANETARY SCIENCES

Guest Editors: Patrick Cordier (Université de Lille and Institut Universitaire de France, France) and Jennifer Jackson (California Institute of Technology, USA)

Understanding the physical and transport properties of minerals is essential for deciphering geophysical and planetary processes. Building on Haüy’s early recognition of the link between crystal structure and macroscopic behavior, modern spectroscopic, thermal, mechanical, electrical, and magnetic techniques now probe these properties across all scales—from atoms to planets. This issue of Elements explores how minerals respond to external fields. Those interactions reveal clues about the past history of the minerals and influence of dynamic processes that continue to shape the Earth and other planetary bodies at present. This issue presents key concepts in mineral physics alongside recent technological advances that enhance our ability to study planetary interiors. Through selected research areas, the issue illustrates how this knowledge deepens our understanding of planetary evolution and highlights the major scientific challenges that lie ahead.

• From Atoms to Planets: The Physics of Minerals Across Scales Jennifer Jackson (California Institute of Technology, USA) and Patrick Cordier (Université de Lille and Institut Universitaire de France, France)
• Illuminated Worlds: How Spectroscopy Lights the Way in Earth, Environmental and Planetary Sciences Natalia Solomatova (Miraterra Technologies and Arca Climate Technologies, Canada), Eva Scheller (Stanford University USA), and Samantha Trumbo (University of California San Diego, USA)
• The Heat is On: Thermal Transport and Melting Jennifer Jackson (California Institute of Technology, USA), Vasilije Dobrosavljevic (Carnegie Institution for Science, USA), and Kenji Ohta (Institute of Science Tokyo, Japan)
• Carrying the Planet on their Backs: How Minerals Respond to Stress Mattia Luca Mazzucchelli (Université de Lausanne, Switzerland), Patrick Cordier (Université de Lille, France), and Claudia Trepmann (Ludwig-Maximilians-Universität München, Germany)
• Plugged-in Planet: Accessing the Interior of the Earth and Other Terrestrial Bodies via Electrical Properties Anne Pommier (Carnegie Institution for Science, USA), Michael Tauber (University of California San Diego, USA), Kate Selway (University of Tasmania, Australia), and Daniel Heyner (Technische Universität Braunschwei, Germany)
• Paleomagnetic Recording at the Grain Scale Roger Fu (Harvard University, USA) and Richard Harrison (University of Cambridge, UK)

• Earth’s Carbon Cycle Thermostat: Beyond the Textbook Model (February 2026)
• Discovery of Volatiles on the Moon: Renaissance in Lunar Exploration Science & Beyond (April 2026)
• Mineral Physics Applied to Earth and Planetary Sciences (June 2026)
• Quartz (August 2026)
• Stromatolites – Deep Time Geochemical Archives of Microbial Ecosystems on Earth (October 2026)
• Zeolites (December 2026)