Mapping the location of terrestrial impacts and extinctions onto the spiral arm structure of the Milky Way

Abstract

High-density regions within the spiral arms are expected to have profound effects on passing stars. Understanding of the potential effects on the Earth and our Solar System is dependent on a robust model of arm passage dynamics. Using a novel combination of data, we derive a model of the timings of the Solar System through the spiral arms and the relationship to arm tracers such as methanol masers. This reveals that asteroid/comet impacts are significantly clustered near the spiral arms and within specific locations of an average arm structure. The end-Permian and end-Cretaceous extinctions emerge as being located within a small star-formation region in two different arms. The start of the Solar System, greater than 4.5 Ga, occurs in the same region in a third arm. The model complements geo-chemical data in determining the relative importance of extra-Solar events in the diversification and extinction of life on Earth.

Catalog of spiral arm tangents (Galactic longitudes) in the Milky Way, and the age gradient based on various arm tracers

“…Elsewhere, results published so far include these: a) an estimate of the angular speed of the density wave spiral pattern (shock front) -Vallée (2021a); b) an estimate and variation of the spiral arm width, from multi-tracers, with increasing Galactic radius -Vallée (2020a); c) an estimate of the co-rotation radius in the disk of the Milky Way -Vallée (2019); d) an estimate of the large-scale pitch angle of each spiral arm, using arm tangents from two Galactic quadrants -Vallée (2017a), Vallée ( 2015); e) an estimate of the starting point of each spiral arm, near the Galactic nucleus -Vallée (2016a); f) a location of a mirror image of arms, across the Galactic Meridian -Vallée (2016b); g) a comparison of 4 different theories for the formation of spiral arms -Vallée (2022); h) mapping the terrestrial impacts (extinctions) in time onto the passage of spiral arm structures (arm tracers) - Gillman et al (2019).…”

The lunar surface as a recorder of astrophysical processes

“…As the Galaxy appears to have four major spiral arms [45], this implies spiral arm passages every ~180 to 440 Myr, during which periods the Solar System may have experienced a range of interesting astrophysical phenomena including nearby supernova (SN) explosions and transits through dense interstellar clouds. Reconstructing this history would provide astronomically valuable information on the structure and evolution of the Galaxy, as well as astrobiologically important information relevant for understanding the past habitability of our own planet [46][47][48][49]. Previous attempts to find correlations between spiral arm crossings and Earth's climate and extinction records have been controversial and ambiguous (e.g.…”

“…It has long been speculated that the changing gravitational potential as the Solar System oscillates above and below the galactic plane, and passes through galactic spiral arms, may perturb the orbits of comets in the Oort Cloud and increase the impact cratering rate in the inner Solar System (e.g. [46,49,55,[87][88][89]). Identifying possible periodicities and/or episodic spikes in the impact cratering rate, which might then be correlated with the Solar System's galactic environment, is problematical primarily because the terrestrial impact record is so sparse [90].…”

Constraining the Evolutionary History of the Moon and the Inner Solar System: A Case for New Returned Lunar Samples

“…The lunar regolith also preserves a record of changes of the Solar System galactic environment as a whole (Spudis 1996). Over the past 4.5 billion years the Solar System has orbited the centre of the Milky Way approximately 20 times (e.g., Gies and Helsel 2005) and passed through spiral arms 2 to 6 times (Gillman et al 2019). While moving around the Galaxy, the lunar regolith could have recorded changes in the flux and types of impactors delivered to the inner Solar System (see Sect.…”