How passage through the Milky Way's spiral arms altered our planet

"The chemical make-up of crystals that formed from magma hint at an increase in the number of meteorites battering Earth's surface."

"Earth's journey through the Milky Way's dense spiral arms might have churned up the planet's surface."

Chemical compositions of crystals formed from magma record elevated levels of extraterrestrial material, indicating an increase in meteorite bombardment on Earth's surface. Variations in trace elements and isotopes within those crystals point to pulses of impact-derived material being incorporated into magmatic systems. Periods of enhanced meteorite flux coincide with Earth's passage through denser segments of the Milky Way, particularly its spiral arms. Gravitational perturbations and increased comet and asteroid delivery during spiral-arm crossings could have increased surface impacts, disrupting crustal surfaces and injecting extraterrestrial material into magmas that later crystallized.

Read at Nature