Mercury's crustal magnetization indicates a stronger ancient dynamo

• 成果类型: Article
• 署名作者: Narrett, Isaac S.; Weiss, Benjamin P.; Steele, Sarah C.; Biersteker, John B.
• 署名单位: Massachusetts Institute of Technology (MIT); Harvard University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2608701123
• 发表日期: 2026-09-01
• 页码: e2608701123
• 关键词: planetary magnetism; mercury; crustal fields; dynamos; magnetohydrodynamics; THERMOCHEMICAL EVOLUTION; GLOBAL CONTRACTION; SOLAR-WIND; field; surface; models; origin; terrestrial; convection; meteorites

摘要

Mercury is the only terrestrial planet in the solar system other than Earth with an active dynamo magnetic field (similar to 200 nT at the equatorial surface). Furthermore, Mercury's similar to 3.9-to 3.7-billion-year-old (Ga) crust is strongly magnetized (similar to 10 nT at similar to 30-km altitude), indicating the presence of a past dynamo. However, the strength of the past dynamo field and the mechanism that generated it are unknown. To address this, we performed three-dimensional magnetohydrodynamic simulations of the ancient solar wind interaction with the planetary field coupled with crustal thermal evolution and magnetization models. We show that the crustal magnetization was likely produced by a dipole field with equatorial surface strength of at least similar to 2,000 nT and possibly as high as similar to 30,000 nT for a dynamo with a reversal frequency greater than once per million years. Such strong fields likely exclude both the solar wind feedback and thermoelectric dynamo mechanisms at similar to 3.7 Ga ago. Instead, our results are compatible with the past dynamo being generated by a nearly fully convective core.