The galactic cycle of extinction

Abstract

: Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

Astrobiological Phase Transition: Towards Resolution of Fermi’s Paradox

“…Following the seminal work of Alvarez et al (1980), we have become aware that discrete and multiple global catastrophes played very a significant role in the overall evolution of our terrestrial biosphere (e.g., Raup 1991;Courtillot 1999;Erwin 2006). Moreover, some of the actual catastrophes whose remarkable traces are seen in the geological record are of astrophysical origin, emphasizing the new paradigm according to which the Solar System is an unclosed system, strongly and openly interacting with its immediate galactic environment (e.g., Clube and Napier 1990;Leitch and Vasisht 1998;Shaviv 2002;Melott et al 2004;Pavlov et al 2005;Gies and Helsel 2005;Gillman and Erenler 2008). This neocatastrophist tendency is present both in the "rare Earth" camp, in the ongoing research on biogenesis (e.g., Raup and Valentine 1983;Maher and Stevenson 1988), and even in the debates on evolution of humanity (Rampino and Self 1992;Ambrose 1998;Bostrom and Ćirković 2008), but all its ramifications have not yet been elucidated in any detail.…”

Periodic Signals of the Milky Way Concealed in Terrestrial Sedimentary Basin Fills and in Planetary Magmatism?

“…With four spiral-arms of the rotating Milky Way along the orbit of the sun (Figure 5), as suspected e.g. by [59], the circular orbit around the galactic center of the somewhat faster solar system lasts approximately 4 × 150 = 600 million years (range: 4 × 137 = 548 [21] to 4 × 176 = 704 million years [60]). Presently, the solar system is located in a small turn-off, the Orion-Spur, between the Sagittarius-Carina and Perseus spiral-arms [57].…”

Cosmophysical situation in the epoch of the Cambrian explosion

“…Meanwhile, for the last 500 m.y., the Sun has crossed four galactic arms and the terrestrial biosphere has faced at least six con siderable mass extinctions that occurred after the Cambrian explosion (Gillman and Erenler, 2008). During that time, there were three superchrons (dated 485-463, 312-264, and 120-84 Ma).…”

“…Since supernova outbursts are considered to be the main source of GCR, a frequency of their occurrence is an important factor determining the cosmophysical environment of the Solar System. During its orbital movement round the Galaxy center, the Sun crosses the star arms and slightly changes its position (oscillates) relative to the Galaxy plane (Gillman and Erenler, 2008).…”