Overview

• The Peking University–USC team analyzed travel‑time changes from global quakes, including 121 repeater events near the South Sandwich Islands (1991–2023), and found the inner core’s motion slowed to a standstill relative to the crust and began reversing around 2008.
• Data indicate a transition from earlier eastward “superrotation” to a slower westward “subrotation,” with the latest phase moving two to three times more slowly than the prior period.
• Researchers say similar slowdowns and reversals appear on multi‑decade cycles of roughly 60–70 years, and any surface effects would emerge gradually.
• Potential consequences include subtle millisecond shifts in day length and long‑term changes to the magnetic field that could affect satellites, communications and animal navigation.
• A separate Oxford‑Leeds‑UCL study reports at least 3.8% carbon in Earth’s core shaping crystallization and geodynamo longevity, while a new Nature paper using NASA InSight data finds Mars has a solid inner core about 613 kilometers in radius, informing planetary dynamo models.