Gamma Ray Bursts Effects on Extinction and Survivability in the Galaxy

Abstract

High-energy astrophysical events, particularly Gamma Ray Bursts (GRBs), have been proposed as significant contributors to mass extinction events on Earth-like planets in most of the galaxy, internal to our radius in it. This paper examines the extent to which GRBs may reset the evolutionary progress of complex life through repeated extinction-level disruptions. While resilient extremophiles may survive even the most intense GRBs, more complex surface-dwelling organisms are vulnerable to indirect atmospheric effects, primarily UV exposure following ozone depletion. By identifying evolutionary milestones and estimating how frequently GRBs would need to occur to prevent recovery between such milestones, this work proposes that GRBs could act as evolutionary filters, limiting the emergence of advanced life, but only much closer to the galactic center. We consider the implications for searches of various biosignatures versus technosignatures.

Figures (5)

• Figure 1: Comparison of GRB risk-level zones in our galaxy, by radius. The bottom half reproduces the estimates from Paper I. The top half shows our re-evaluated risk zones, derived from the shorter exposure windows. We present both the conservative (200 Myr, right) and aggressive (100 Myr, left) ancestral exposure windows, defined by the expected number of lethal GRBs $\bar{N}$ per window at each galactic radius. The Earth's galactic location is marked relative to a model background by NASA/JPL-Caltech/R. Hurt (SSC/Caltech) (ssc2008-10a).
• Figure 2: The phenomenon, represented by three stages. Seen in the figure: a G-type main-sequence star (yellow), an Earth-like planet (blue-green yinyang), a GRB (beige), an ozone layer (gray), NO$_{y}$ layer Perros (red). The relevant electromagnetic radiation is shown in the legend found in the top-left of the figure. The penetration of electromagnetic radiation is shown qualitatively by the meeting of the radiation arrow with the layer (radiation is mostly returned/scattered) or the continuation of the radiation through the layer (radiation penetrates the layer).
• Figure 3: Attenuation of electromagnetic radiation through Earth-relevant environments. X-ray data from CXRO Henke; shortwave water data from NIST Hubbell; UV/visible/IR for water from Segelstein Segelstein; and for NO2 from Schneider Schneider. UV data for solid Al2O3 and Fe2O3 from Querry Querry, SiO2 from Herbin Herbin.
• Figure 4: Comparison of Earth's Azimuthal Equidistant projection (AEQD) maps at 0 Mya, 360 Mya, and 445 Mya. These refer to the clustering of Earth's land today, at maximal clustering for 100% land, and at maximal clustering for 90% land, respectively. Inner reference circles (small circles) are drawn at fixed angular distances from the cap center for comparison. Figures written in black refer to the 90% land data, figures written in white refer to the 100% land data.
• Figure 5: A timeline of Earth's evolution showing parameters relevant to GRB risks. The horizontal axis is a broken linear axis: the left third spans 4000-–600 Mya (compressed), and the right two-thirds span 600-–0 Mya (expanded). The oxygen data (thick, in three colors: red for Archaean, blue for Proterozoic, green for Phanerozoic) is from LyonsMills, and follows the left-hand logarithmic concentration scale. The thickness represents the uncertainty of the reconstructions. The general oxygen trend has been that of increase, with shaded regions indicating major oxygenation events, i.e. the Great Oxidation Event (GOE Gumsley) and the NOE Glass. The dashed red line (following the right-hand side axis) shows the probability of a potential GRB hemisphere encompassing at least 90% of land, derived from paleogeographic reconstructions Scotese. This chance has had a generally downwards trend, and has been nil since the Jurassic/Cretaceous boundary. Red X's mark the "Big Five" RaupSepkoskiBond extinction events. We note that paleogeographic data exists further back PISAREVSKY2014207ScoteseLongMERDITH2021103477Muller2022LI2023104336CAO2024101922, but in this work we are not concerned with such early land life. The purple columns represent periods in our evolutionary lineage during which our ancestry was diurnal and hence at risk of UV exposure following a GRB; column edges fade to reflect uncertainty in the timing of these lifestyle transitions (see text for further details).