Muon Radiation Dose and Marine Megafaunal Extinction at the end-Pliocene Supernova

Abstract

Considerable data and analysis support the detection of a supernova at a distance of about 50 pc, ~2.6 million years ago. This is possibly related to the extinction event around that time and is a member of a series of explosions which formed the Local Bubble in the interstellar medium. We build on the assumptions made in previous work, and propagate the muon flux from supernova-initiated cosmic rays from the surface to the depths of the ocean. We find that the radiation dose from the muons will exceed the total present surface dose from all sources at depths up to a kilometer and will persist for at least the lifetime of marine megafauna. It is reasonable to hypothesize that this increase in radiation load may have contributed to a newly documented marine megafaunal extinction at that time. peer-reviewed)

Supernova triggers for end-Devonian extinctions

“…In contrast to the episodic, seasonal, and geographically limited ozone depletion expected from enhanced convection, ozone depletion following a SN is long-lived and global (see, e.g., (16,20,21)) and is therefore much more likely to lead to an extinction event, even given uncertainties around the level of depletion necessary. (We note that, as well as the induced UV-B damage, cosmic rays could also cause radiation damage via muons produced when they impact the atmosphere (22)). The SN blast itself is unlikely to wreak significant damage on the biosphere, but may deposit detectable long-lived nuclear isotopes that could provide distinctive signatures, as we discuss later.…”

“…Cosmic rays striking the atmosphere produce energetic muons that can penetrate matter to a much larger depth than UV-B radiation. The radiation dose due to muons at the Earth's surface (34) and in the oceans at depths 1 km (22) could exceed for many years the current total radiation dose at the Earth's surface from all sources. Therefore, in addition to comparing the effects of muons and UV-B radiation at or near the surface, they could be considered in end-Devonian extinctions of megafauna living at depth.…”

Climate change via CO2 drawdown from astrophysically initiated atmospheric ionization?

“…If we add in the cosmic ray trapping effect of the magnetic field in the walls of the Local Bubble and/or multiple supernovae (Breitschwerdt et al ., 2016) the duration of the effect may be greater. Muon irradiation has the additional effect of affecting life up to a kilometre below the surface of the ocean (Melott and Thomas, 2018; Melott et al ., 2019). Nevertheless, only a small increase in mutation and carcinogenesis is expected for phytoplankton, although the effect may be large for megafauna (Melott et al ., 2019).…”

“…Muon irradiation has the additional effect of affecting life up to a kilometre below the surface of the ocean (Melott and Thomas, 2018; Melott et al ., 2019). Nevertheless, only a small increase in mutation and carcinogenesis is expected for phytoplankton, although the effect may be large for megafauna (Melott et al ., 2019). We conclude that muon irradiation is a small competing effect with regard to atmospheric chemistry.…”

“…(1999). Recent studies of the effects upon the Earth of such an event have included enhanced solar ultraviolet-B (UVB 280–315 nm) due to ozone depletion, visible light effects on nocturnal organisms, increased radiation from cosmic ray secondaries (primarily muons and neutrons) and direct deposition of cosmogenic radioisotopes (Melott et al ., 2017; Melott and Thomas, 2018; Thomas, 2018; Melott et al ., 2019).…”