Ionizing radiation is known to have a destructive effect on biology by causing damage to DNA, cells and the production of reactive oxygen species, among other things. While direct exposure to high-radiation dose is indeed not favorable for biological activity, ionizing radiation can and, in some cases, is known to produce a number of biologically useful products. One such mechanism is the production of biologically useful products via charged particle-induced radiolysis. Energetic charged particles interact with the surfaces of planetary objects such as Mars, Europa and Enceladus without much shielding from their rarefied atmospheres. Depending on the energy of said particles, they can penetrate several meters deep below the surface and initiate a number of chemical reactions along the way. Some of the byproducts are impossible to produce with lower-energy radiation (such as sunlight), opening up new avenues for life to utilize them. The main objective of the manuscript is to explore the concept of a Radiolytic Habitable Zone (RHZ), where the chemistry of galactic cosmic ray-induced radiolysis can be potentially utilized for metabolic activity. We first calculate the energy deposition and the electron production rate using the GEANT4 numerical model, then estimate the current production and possible chemical pathways which could be useful for supporting biological activity on Mars, Europa and Enceladus. The concept of RHZ provides a novel framework for understanding the potential for life in high-radiation environments. By combining energy deposition calculations with the energy requirements of microbial cells, we have defined the RHZ for Mars, Europa and Enceladus. These zones represent the regions where radiolysis-driven energy production is sufficient to sustain microbial metabolism. We find that bacterial cell density is highest in Enceladus, followed by Mars and Europa. We discuss the implications of these mechanisms for the habitability of such objects in the solar system and beyond.

Comets are a source of prebiotic molecules that likely enriched the early Earth during the Late Heavy Bombardment period. Laboratory experiments that replicate cometary conditions may facilitate understanding of the chemical reactions and supplement observational studies of these icy bodies. Prebiotic compounds, such as formic acid and formaldehyde, have been observed in comets. Furthermore, these compounds can easily be formed in experimental models using a variety of gas combinations and energy sources. We conducted experimental cometary simulations using radiation chemistry tools to obtain insight into the possible fate of formic acid and formaldehyde. The main results suggest a redundant system, signifying that the irradiation of formic acid forms formaldehyde molecules and vice versa. This phenomenon ensures the permanence of prebiotic molecules in high-radiation environments. Additionally, the potential role of forsterite and graphite was explored in cometary simulations. Our experimental results show the differential formation of aldehydes and other carbonyl-containing compounds dependent on the mineral phase present.

Bacillus pumilus SAFR-032, an endospore-forming bacterial strain, was investigated to determine its methylation pattern (methylome) change, compared to ground control, after direct exposure to space conditions onboard the International Space Station (ISS) for 1.5 years. The resulting ISS-flown and non-flown strains were sequenced using the Nanopore MinION and an in-house method and pipeline to identify methylated positions in the genome. Our analysis indicated genomic variants and m6A methylation increased in the ISS-flown SAFR-032. To complement the broader omics investigation and explore phenotypic changes, ISS-flown and non-flown strains were compared in a series of laboratory-based chamber experiments using an X-ray irradiation source (doses applied at 250, 500, 750, 1000 and 1250 Gy); results show a potentially higher survival fraction of ISS-flown DS2 at the two highest exposures. Taken together, results from this study document lasting changes to the genome by methylation, potentially triggered by conditions in spaceflight, with functional consequences for the resistance of bacteria to stressors expected on long-duration missions beyond low Earth orbit.

This study aimed at comparing neuropsychological test scores in 83 cardiologists and nurses (exposed group, EG) working in the cardiac catheterization laboratory, and 83 control participants (non exposed group, nEG), to explore possible cognitive impairments. The neuropsychological assessment was carried out by means of a battery called “Esame Neuropsicologico Breve.” EG participants showed significantly lower scores on the delayed recall, visual short-term memory, and semantic lexical access ability than the nEG ones. No dose response could be detected. EG participants showed lower memory and verbal fluency performances, as compared with nEG. These reduced skills suggest alterations of some left hemisphere structures that are more exposed to IR in interventional cardiology staff. On the basis of these findings, therefore, head protection would be a mandatory good practice to reduce effects of head exposure to ionizing radiation among invasive cardiology personnel (and among other exposed professionals). (JINS, 2015, 21, 670–676)

The Earth is constantly struck by radiation coming from the interstellar medium. The very low energy end of the spectrum is shielded by the geomagnetic field but charged particles with energies higher than the geomagnetic cutoff will penetrate the atmosphere and are likely to interact, giving rise to secondary particles. Some astrophysical events, such as γ-ray bursts and supernovae, when happening at short distances, may affect the planet's biosphere, due to the temporary enhanced radiation flux. Muons are abundantly produced by high-energy cosmic rays in the Earth's atmosphere. These particles, due to their low cross-section, are able to penetrate deep both underground and underwater, with the possibility of affecting biological niches normally considered shielded from radiation. We investigate the interaction of muons produced by high-energy cosmic rays on the Earth's atmosphere using the Geant4 toolkit. We analyse its penetration power in water and crust and also the interaction effects within bacteria-like material according to the particle type and energy, and noticed the possibility of off-track damage due to secondary particles.

The aim of the paper is to present the time profile of cosmic radiation exposure obtained by the radiation risks radiometer-dosimeter (R3DR) during the ESA exposition facility for EXPOSE-R mission (EXPOSE-R) in the EXPOSE-R facility outside the Russian Zvezda module of the International Space Station (ISS). Another aim is to make the obtained results available to other EXPOSE-R teams for use in their data analysis. R3DR is a low mass and small dimensions automated device, which measures solar radiation in four channels and in addition cosmic ionizing radiation. The main results of cosmic ionizing radiation measurements are: three different radiation sources were detected and quantified: galactic cosmic rays (GCR), energetic protons from the inner radiation belt (IRB) in the region of the South Atlantic anomaly and energetic electrons from the outer radiation belt (ORB). The highest daily averaged absorbed dose rate of 506 μGy day−1 came from IRB protons; GCR delivered much smaller daily absorbed dose rates of 81.4 μGy day−1 on average, and ORB source delivered on average a dose rate of 89 μGy day−1. The IRB and ORB daily averaged absorbed dose rates were higher than those observed during the ESA exposition facility for EXPOSE-E mission (EXPOSE-E), whereas the GCR rate was smaller than that measured during the EXPOSE-E mission. The reason for this difference is much less surrounding constructions shielding of the R3DR instrument in comparison with the R3DE instrument.

La fabrication de verre plombé n’a pas encore été développée en Colombie, ce qui entraîne des lacunes dans la recherche d’améliorations des composants pour la protection radiologique. Le Groupe de Physique Médicale de l’Université Nationale de Colombie a donc initié une étude en vue de développer différents échantillons de verre plombé qui soient adaptés à une utilisation comme blindage contre les rayonnements ionisants. Les caractéristiques optimales ont été trouvées pour une concentration de 50 % d’oxyde de plomb (PbO) dans un verre de plomb-silicate. Un pourcentage de PbO supérieur entraîne des difficultés techniques et une diminution de la clarté du verre. Pour cette fraction molaire nous avons trouvé un coefficient d’absorption linéaire de 0,35 cm-1, c’est-à-dire que pour une énergie de 662 keV un centimètre de ce verre correspond à 3,0 mm de plomb pur; avec cette même énergie la couche de demi-atténuation (CDA) de l’échantillon est égale à celle du ciment ferreux utilisé couramment dans les blindages radiologiques. Enfin il a également été observé que l’application d’une couche d’air de 1 cm entre les lames de verre diminue la transmission des photons jusqu’à 20 % pour le verre contenant 40 % de plomb.

For 63 years scientists in the Atomic Bomb Casualty Commission and its successor, the Radiation Effects Research Foundation, have been assessing the long-term health effects in the survivors of the atomic bombings of Hiroshima and Nagasaki and in their children. The identification and follow-up of a large population (approximately a total of 200 000, of whom more than 40% are alive today) that includes a broad range of ages and radiation exposure doses, and healthy representatives of both sexes; establishment of well-defined cohorts whose members have been studied longitudinally, including some with biennial health examinations and a high survivor-participation rate; and careful reconstructions of individual radiation doses have resulted in reliable excess relative risk estimates for radiation-related health effects, including cancer and noncancer effects in humans, for the benefit of the survivors and for all humankind. This article reviews those risk estimates and summarizes what has been learned from this historic and unique study.

(Disaster Med Public Health Preparedness. 2011;5:S122-S133)

On présente un bref exposé des activités de métrologie de la dose du Laboratoire National Henri Becquerel (LNE-LNHB), laboratoire national de métrologie pour les rayonnements ionisants. Les résultats des principaux travaux effectués ces dernières années dans ce domaine sont exposés, en particulier les développements se rapportant aux calculs par simulation Monte Carlo, aux instruments étalons (calorimètres, chambres d’ionisation) et aux références dosimétriques pour la radiothérapie, le radiodiagnostic et la radioprotection.

The effects of ionizing radiation on MOS transistors with gate oxide thickness up to 2 μm have been investigated. The major focus of workers in this area has been on the hardening techniques of technologies. On the other side, our goal is to use MOS devices to reach higher sensitivities in order to detect small amounts of dose. Therefore, sensitivity as well as temperature response in the mil-std range and stability of the dosimeters have been studied.