Ionizing radiation and life

Ionizing radiation is a ubiquitous feature of the Cosmos, from exogenous cosmic rays (CR) to the intrinsic mineral radioactivity of a habitable world, and its influences on the emergence and persistence of life are wide-ranging and profound. Much attention has already been focused on the deleterious effects of ionizing radiation on organisms and the complex molecules of life, but ionizing radiation also performs many crucial functions in the generation of habitable planetary environments and the origins of life. This review surveys the role of CR and mineral radioactivity in star formation, generation of biogenic elements, and the synthesis of organic molecules and driving of prebiotic chemistry. Another major theme is the multiple layers of shielding of planetary surfaces from the flux of cosmic radiation and the various effects on a biosphere of violent but rare astrophysical events such as supernovae and gamma-ray bursts. The influences of CR can also be duplicitous, such as limiting the survival of surface life on Mars while potentially supporting a subsurface biosphere in the ocean of Europa. This review highlights the common thread that ionizing radiation forms between the disparate component disciplines of astrobiology.

A 17-year oscillation in cancer mortality birth cohorts on three continents - synchrony to cosmic ray modulations one generation earlier

Cross-generational effects (grandmother effects) associated with epigenetic imprinting, environmental exposures, and lifestyle choices are beginning to be explored by various investigators. The possibility that low-level background radiation can be a driver of such effects has been suggested previously and is explored further in this study. Age-period-cohort analysis was performed on United States (US), United Kingdom (UK), and Australian (AU) female breast cancer mortality of the twentieth century, as well as on UK female total cancer mortality, to extract the high-frequency oscillations in the birth cohort time series. US fetal and infant congenital mortality were examined to extend the birth cohorts to modern times. A approximately 17-year cycle was detected in all birth cohort series, which spanned approximately 180 years from 1820 to 2000. This suggests a global, environmental cause. To mimic previous work in examining a possible link to cosmic radiation, the 17- to 18-year cycles of the cosmogenic nuclide (14)C, the sunspot double-cycle, neutron monitors, and a compilation of ground-based magnetic field observations were examined in the birth cohort and germ cell cohort time frames. Evidence is presented that optimal alignments with extraterrestrial oscillations occur in the time frame of the germ-cell cohort, one generation before the birth cohorts. Furthermore, the alignment is optimized by accounting for the changes in the maternal age distribution over time. These findings have potential importance to the mechanisms of disease as well as species adaptation and evolution.

Long-term cycles in the history of life: periodic biodiversity in the paleobiology database

Time series analysis of fossil biodiversity of marine invertebrates in the Paleobiology Database (PBDB) shows a significant periodicity at approximately 63 My, in agreement with previous analyses based on the Sepkoski database. I discuss how this result did not appear in a previous analysis of the PBDB. The existence of the 63 My periodicity, despite very different treatment of systematic error in both PBDB and Sepkoski databases strongly argues for consideration of its reality in the fossil record. Cross-spectral analysis of the two datasets finds that a 62 My periodicity coincides in phase by 1.6 My, equivalent to better than the errors in either measurement. Consequently, the two data sets not only contain the same strong periodicity, but its peaks and valleys closely correspond in time. Two other spectral peaks appear in the PBDB analysis, but appear to be artifacts associated with detrending and with the increased interval length. Sampling-standardization procedures implemented by the PBDB collaboration suggest that the signal is not an artifact of sampling bias. Further work should focus on finding the cause of the 62 My periodicity.