Dossier
Tim Johnson
Coverage of Tim Johnson in the Nexus archive.
- The missing 500 million: Cosmic bombardment melted Earth's first crust
Geologists debate how Earth's continents formed, with some arguing that an intense asteroid bombardment 4 billion years ago melted the early crust, enabling buoyant continental crust. The oldest continental rocks date to 4.03 billion years ago, but evidence from Earth's first 500 million years is scarce.
- Asteroid bombardment may have delayed Earth’s first continents
Research from Curtin University and Queensland University of Technology suggests repeated asteroid impacts during Earth's Hadean era injected heat into the planet's interior, keeping the crust hot and unstable. This delayed the formation of stable continents by preventing the crust from solidifying, according to a study published in Science.