Remarkable migration of the solar system from the innermost Galactic disk; a wander, a wobble, and a climate catastrophe on the Earth

TL;DR

This paper explores how the solar system's radial migration within the Milky Way, driven by spiral arm encounters, may have caused climate catastrophes on Earth, including multiple snowball Earth events.

Contribution

It combines chemical evolution data, isotopic analysis, and numerical simulations to propose a dynamic history of the solar system's migration and its impact on Earth's climate.

Findings

Solar system likely migrated from the Galactic bulge to its current position.

Radial migration episodes correlate with Earth's snowball Earth events.

Multiple passages through spiral arms caused rapid climate changes on Earth.

Abstract

Recent knowledge of Galactic dynamics suggests that stars radially move on the disk when they encounter transient spiral arms that are naturally generated during the process of disk formation. We argue that a large movement of the solar system from the innermost disk over its lifetime is inferred from a comparison of the solar composition with those of solar twins within the Galactic chemical evolution framework. The implied metal-rich environment at the Sun's birthplace and formation time is supported by measured silicon isotopic ratios in presolar silicon carbide grains. We perform numerical simulations of the dynamical evolution of disk stars in a Milky Way-like galaxy to identify the lifetime trajectory of the solar system. We find that a solar system born in the proximity of the Galactic bulge could travel to the current locus by the effect of radial migration induced by several major encounters with spiral arms. The frequent feature we identify is the repeated passages of stars inside the same spiral arm owing to the wobble of stars traveling in and out of the spiral arms. We predict that such episodes are evidenced in the Earth's geological history as snowball Earth and that their occurrence times are within our prediction. In particular, the stellar motion that vertically oscillates during passages through spiral arms occasionally leads to a split into two discrete passage episodes with an interval of several tens of Myr, implying two relevant snowball Earth events that occurred in rapid succession (~7.2 and 6.5 hundred Myr ago).