Identifying the Presence of Natural Radionuclides in Ashlar Samples

The high-energy radiation environment of exoplanets can greatly affect their atmospheric chemistry through photo-chemical reactions and ionisation of the upper parts of the atmospheres. In order to analyse the chemistry of exoplanet atmospheres, it is therefore necessary to understand the radiative environment the planet is placed in and what effects it has on the atmosphere.  The aim of this project is to study how the chemistry of exoplanet atmospheres is affected by the radiative environment. We focus on three different sources of high-energy radiation; the XUV radiation of the host star, the stellar energetic particles (SEPs) of the host star, and the galactic cosmic rays (GCRs) originating from outside the planetary system. We model the disequilibrium chemistry of a gas giant test planet, using the chemical kinetic network, STAND2020, coupled to the 1D photo-chemistry and diffusion code, ARGO. The radiative sources are introduced in the models as spectral energy distributions for the XUV radiation, and as ionisation rates for for the SEPs and GCRs. STAND2020 excels by its complexity in H/C/N/O chemistry which allows us to study the effect of the irradiation on larger complex molecules such as prebiotic molecules and haze precursors.  In this talk, we present a grid of models run for host stars of the types; O,B,A,F,G,K, and M, under varying influxes of GCRs. For each of the stellar spectral types a representative spectra, combined from observations and models, has been chosen from a comprehensive search of recent literature. The SEP flux for each stellar type is approximated from the stellar activity by scaling the solar SEP spectrum based on observations of X-ray flares. The GCR flux is varied step-wise from no GCRs (representative of a system that is highly shielded by the heliosphere of an active host star) to GCR fluxes estimated for the ISM in the central part of the galaxy (representative of a system in a highly radiative galactic environment with a weak heliosphere of a quiet host star). This grid over radiative environments allows us an insight into the effects of high-energy radiation on atmospheric chemistry, and can help guide our analysis of exoplanet atmosphere observations based on the stellar type of the host star and the environment the system is located in.

view Abstract Citations (264) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the anisotropy of the cosmological background matter and radiation distribution. I - The radiation anisotropy in a spatially flat universe Wilson, M. L. ; Silk, J. Abstract The expected anisotropy in the microwave background radiation on both large and small angular scales has been calculated. Primordial adiabatic and isothermal fluctuations are considered for a variety of initial power-law fluctuation spectra |δm(k)|2 ∝ kn in a spatially flat universe. The calculated temperature anisotropy on small angular scales is below the current observational upper limits if Ω ≳ 1. An appreciable dipole and smaller quadrupole anisotropy are also produced. These are generated by fluctuations in the mean gravitational potential associated with small-amplitude large- wavelength fluctuations in the matter distribution on scales &≳10-100 Mpc. Most of the observed dipole anisotropy could be attributed to this effect, as could the possible detection of a quadrupole anisotropy. More generally, the large-scale radiation anisotropy measurements constrain the index of the initial fluctuation spectrum: n ≳ 0 for isothermal fluctuations and n ≳ 3 for adiabatic fluctuations. A further implication is that, in general, our peculiar velocity relative to distance shells of matter only coincides with that measured relative to the background radiation (inferred from the dipole moment) at a redshift z ≳ 0.1. At small redshifts there can be significant deviations in both direction and amplitude. Publication: The Astrophysical Journal Pub Date: January 1981 DOI: 10.1086/158561 Bibcode: 1981ApJ...243...14W Keywords: Anisotropy; Background Radiation; Cosmic Rays; Cosmology; Microwaves; Relic Radiation; Universe; Adiabatic Equations; Anisotropic Media; Dipole Moments; Fluctuation Theory; Isothermal Processes; Quadrupoles; Radiation Spectra; Red Shift; Astrophysics full text sources ADS |

Distribution and behaviour of natural radionuclides in soil samples of Goa on the southwest coast of India

[1] The United States is preparing to return humans to the Moon and is setting the stage for exploration to Mars and beyond. However, it is unclear if long missions outside of low-Earth orbit (LEO) can be accomplished with acceptable risk. The central objective of the NASA Living With a Star Earth-Moon-Mars Radiation Environment Module (EMMREM) is to develop and validate a numerical module for completely characterizing time-dependent radiation exposure in the Earth-Moon-Mars and interplanetary space environments. EMMREM currently provides the capability to predict radiation exposure in the interplanetary environment outside of Earth’s protective atmosphere and magnetosphere and at various heights of a nominal Mars atmosphere. Ongoing and future efforts will fold in the effects of Earth’s atmosphere and the geomagnetic field so that the radiation environment can be predicted near the Earth’s surface, at LEO, and at various geomagnetic latitudes. EMMREM is being designed for broad use by researchers to predict radiation exposure by integrating over time-evolving incident particle distributions from interplanetary space. The EMMREM represents a growing and developing system of coupled models that describe particle acceleration and transport in interplanetary space and secondary transport through shielding materials, atmospheres, and various parts of the human body to determine doses, dose rates, and linear energy transfer spectra. Thus, EMMREM makes the explicit connection from observations and simulations of solar energetic particles and galactic cosmic rays to characterization of the potential hazards of the radiation environment and to acute radiation risks. The papers in this special section will describe the following. [2] 1. Observations near 1 AU from ACE, GOES, and IMP 5 for the historic August 1972 event to characterize the near-Earth radiation environment are used as timedependent boundary conditions near 1 AU in an energetic particle propagation and acceleration module (the Energetic Particle Radiation Environment Module (EPREM)) to predict the radiation environment throughout the inner heliosphere. Observations at Ulysses (near 5 AU) are then used to validate the EPREM predictions. [3] 2. Event-based simulations in the inner heliosphere predict time-dependent estimates of organ exposures for human crews in deep space. [4] 3. A paper provides a risk assessment approaches for solar particle events. [5] 4. Several papers describe a model for prompt solar energetic particle (SEP) dose rate forecasting for the Earth-Moon system. [6] 5. The transmission of SEPs and galactic cosmic rays (GCRs) through the Mars atmosphere predicts the radiation environment at Mars. [7] 6. The coupling between the Energetic Particle Radiation Environment Module and magnetohydrodynamic models improves the predictions of the radiation environment in the inner heliosphere. [8] 7. Ulysses observations and a model of GCRs are used to improve our understanding of recent GCR fluxes and associated GCR dose rates throughout the inner heliosphere. [9] 8. A paper provides predictions of the linear energy transfer spectrum for the Cosmic Ray Telescope for the Effects of Radiation detector during the Lunar Reconnaissance Orbiter mission. [10] 9. Several papers describe predictions of the space radiation environment during gradual solar energetic particle events using physics-based particle acceleration models. [11] Thus, the papers in this special section of Space Weather introduce the EMMREM project and provide a baseline for current understanding of the space environment beyond Earth’s protective atmosphere and magnetosphere.

Measurement of terrain-emanated natural uranium gamma radiation is difficult because of the inclusion by the measuring device of radiation from the decay of atmospheric radon. This paper presents the results of a 7-year study of time variations of the components of the natural gamma radiation. Accurate measurement and removal of the atmospheric equivalent uranium (eU) decay fraction provides the terrain-emanated eU radiation. Variations in equivalent thorium (eTh), eU, and potassium-40 (40K) natural radiation have been measured over this 7-year period at one location at 5-min intervals. Atmospheric diurnal changes in the concentrations of radon gamma-emitting daughters are observed to exceed surface-emanated eU radiation by more than 400% in the absence of rainfall and up to 3000% in rainfall. Gamma radiation from rainfall-deposited thoron daughters has been seen to increase the surface-emanated eTh radiation by more than 70%. Two different field vehicles currently contain the measurement systems. Data reduction requires the use of environmentally measured gamma ray standard spectra for eTh, eU, and 40K decay and cosmic radiation, plus measurement and use of vehicular system radiation backgrounds. Using these measurement methods, gamma radiation emitted from the earth's surface can be accurately determined day or night, except during and for up to1.5 days following rainfall. Monthly variations of the components of the natural gamma radiation are presented together with daily variations for six selected months of the measurement period.

Particle radiation environment in the heliosphere: Status, limitations, and recommendations

Previous epidemiological studies and quantitative risk assessments (QRA) have suggested that natural background radiation may be a cause of childhood leukemia. The present work uses a QRA approach to predict the excess risk of childhood leukemia in France related to three components of natural radiation: radon, cosmic rays and terrestrial gamma rays, using excess relative and absolute risk models proposed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Both models were developed from the Life Span Study (LSS) of Japanese A-bomb survivors. Previous risk assessments were extended by considering uncertainties in radiation-related leukemia risk model parameters as part of this process, within a Bayesian framework. Estimated red bone marrow doses cumulated during childhood by the average French child due to radon, terrestrial gamma and cosmic rays are 4.4, 7.5 and 4.3 mSv, respectively. The excess fractions of cases (expressed as percentages) associated with these sources of natural radiation are 20 % [95 % credible interval (CI) 0-68 %] and 4 % (95 % CI 0-11 %) under the excess relative and excess absolute risk models, respectively. The large CIs, as well as the different point estimates obtained under these two models, highlight the uncertainties in predictions of radiation-related childhood leukemia risks. These results are only valid provided that models developed from the LSS can be transferred to the population of French children and to chronic natural radiation exposures, and must be considered in view of the currently limited knowledge concerning other potential risk factors for childhood leukemia. Last, they emphasize the need for further epidemiological investigations of the effects of natural radiation on childhood leukemia to reduce uncertainties and help refine radiation protection standards.

The space radiation environment for the CLEMENTINE I mission was investigated using a new calculational model, CHIME, which includes the effects of galactic cosmic rays (GCR), anomalous component (AC) species and solar energetic particle (SEP) events and their variations as a function of time. Unlike most previous radiation environment models, CHIME is based upon physical theory and is {open_quotes}calibrated{close_quotes} with energetic particle measurements made over the last two decades. Thus, CHIME provides an advance in the accuracy of estimating the interplanetary radiation environment. Using this model we have calculated particle energy spectra, fluences and linear energy transfer (LET) spectra for all three major components of the CLEMENTINE I mission during 1994: (1) the spacecraft in lunar orbit, (2) the spacecraft during asteroid flyby, and (3) the interstate adapter USA in Earth orbit. Our investigations indicate that during 1994 the level of solar modulation, which dominates the variation in the GCR and AC flux as a function of time, will be decreasing toward solar minimum levels. Consequently the GCR and AC flux will be increasing during Y, the year and, potentially, will rise to levels seen during previous solar minimums. The estimated radiation environment also indicates that the AC will dominate the energetic particle spectra for energies below 30-50 MeV/nucleon, while the GCR have a peak flux at {approximately}300 MeV/nucleon and maintain a relatively high flux level up to >1000 MeV/nucleon. The AC significantly enhances the integrated flux for LET in the range 1 to 10 MeV/(mg/cm{sup 2}), but due to the steep energy spectra of the AC a relatively small amount of material ({approximately}50 mils of Al) can effectively shield against this component. The GCR are seen to be highly penetrating and require massive amounts of shielding before there is any appreciable decrease in the LET flux.

Natural radiation environment in China

The charged particle radiation environment on Mars measured by MSL/RAD from November 15, 2015 to January 15, 2016

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) measures linear energy transfer by Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) on the Lunar Reconnaissance Orbiter (LRO) Mission in a circular, polar lunar orbit. GCR fluxes remain at the highest levels ever observed during the space age. One of the largest SEP events observed by CRaTER during the LRO mission occurred on June 7, 2011. We compare model predictions by the Earth‐Moon‐Mars Radiation Environment Module (EMMREM) for both dose rates from GCRs and SEPs during this event with results from CRaTER. We find agreement between these models and the CRaTER dose rates, which together demonstrate the accuracy of EMMREM, and its suitability for a real‐time space weather system. We utilize CRaTER to test forecasts made by the Relativistic Electron Alert System for Exploration (REleASE), which successfully predicts the June 7th event. At the maximum CRaTER‐observed GCR dose rate (∼11.7 cGy/yr where Gy is a unit indicating energy deposition per unit mass, 1 Gy = 1 J/kg), GCRs deposit ∼88 eV/molecule in water over 4 billion years, causing significant change in molecular composition and physical structure (e.g., density, color, crystallinity) of water ice, loss of molecular hydrogen, and production of more complex molecules linking carbon and other elements in the irradiated ice. This shows that space weathering by GCRs may be extremely important for chemical evolution of ice on the Moon. Thus, we show comprehensive observations from the CRaTER instrument on the Lunar Reconnaissance Orbiter that characterizes the radiation environment and space weathering on the Moon.

Space system design for lunar orbit and extended operations on the lunar surface requires analysis of potential system vulnerabilities to plasma and radiation environments to minimize anomalies and assure that environmental failures do not occur during the mission. Individual environments include the trapped particles in Earth s radiation belts, solar energetic particles and galactic cosmic rays, plasma environments encountered in transit to the moon and on the lunar surface (solar wind, terrestrial magnetosheath and magnetotail, and lunar photoelectrons), and solar ultraviolet and extreme ultraviolet photons. These are the plasma and radiation environments which contribute to a variety of effects on space systems including total ionizing dose and dose rate effects in electronics, degradation of materials in the space environment, and charging of spacecraft and lunar dust. This paper provides a survey of the relevant charged particle and photon environments of importance to lunar mission design ranging from the lowest (approx.few 10 s eV) photoelectron energies to the highest (approx.GeV) cosmic ray energies.

Radiation can be found naturally or can be created by human-made artificial sources. Radioactive unstable elements divide to become stable, they release the excess energy in their nuclei to their surroundings by producing different types of radiation. This uranium, radium, thorium, potassium, etc. on earth. Cosmic rays coming from the sun and outer space, together with unstable elements, create a certain level of natural radiation in the environment. Therefore, natural radiation comes from many naturally occurring radioactive substances found in the soil, water, air and body in the environment where we spend our daily lives.The intake of natural radioisotopes into the body through digestion varies depending on the consumption rate of food and beverages and the radioisotope concentration. The concentration of radioisotopes naturally found in foods varies depending on the natural background levels, climate and agricultural practices of the region. Likewise, eating habits vary from region to region and country to country.All foods contain radionuclides, which are transferred from soil to crops on land and from water to fish in seas, lakes and rivers. Natural radionuclides in drinking water and food generally have very low levels and are safe for human consumption. In normal situations, a reference level of 1 mSv in a year applies to the individual radiation dose from the consumption of food. The same reference level applies separately to drinking water. These references are determined by the WHO/FAO Codex Alimentarius Commission has established “Guideline Levels” for radionuclides in foods destined for human consumption and traded internationally.

Space radiation physics and application include the theory and the key technologies of studying radiation effects in spacecraft electronics systems and improving the on-orbit survival probability of spacecrafts. It is an interdisciplinary science involving nuclear science and astronautics electronics. The research work mainly covers simulation of radiation environment, interaction between radiation and materials, radiation hardening, as well as radiation measurement and diagnosis. In recent years, new challenges and problems to the research of space radiation physics have arisen along with the rapid development in microelectronics and space technology. Radiation effects, including single event effects, total ionizing dose effects, displacement damage, charging and discharging effects, are one kind of main threats for space applications. The study of space radiation physics and application plays a fundamental role in maintaining the robustness against radiation of the spacecraft electronics systems. Countries like America and Russia have devoted a lot in this field, now they have a whole set of facilities, guidelines and principles to guarantee the fabrication, evaluation, and utilization of the radiation-hardened electronic devices and systems. However, there are still some problems left unsolved. Furthermore, as the fast development of the electronics, new problems emerge quickly. Space radiation environments mainly include the Van Allen trapped belt, Solar cosmic rays, galactic particles. The fluence of the related protons, electrons, and heavy ions are strongly dependent on solar activity and geomagnetic activity. The distribution of particle fluence is highly no uniform. Spacecraft working in different orbits may face diverse radiation environments. To describe the radiation environments, series of models have been developed for describing the distribution of trapped protons and electrons. Although continued being modified, the errors between predicted values and measured ones are still quite large. It is essential to keep working on this area and increase the accuracy. To measure the parameters like categories, fluence, energy and flux of the radiation environments, many types of detectors have been developed. Along with the emergence of new types of material, it is always meaningful to keep improving the performance and efficiency of detectors. Exploring the underlying mechanisms of radiation effects is extremely important for carrying out the research on radiation hardening by design. In the past 50 years, more and more work has been devoted to studying the physical mechanisms and gained valuable results. However, we still do not get the clear whole physical pictures of some well-known effects. Meanwhile, more and more electronic devices with new material and new structures bring new challenge to the mechanism study. To make sure that an electronic system is robust enough to radiation environments, it is necessary to quantify the radiation vulnerability of every electronic device in the system. Through circuit or system simulation, the radiation vulnerability of the whole system can be estimated. At present, it is still difficult to perform this kind of simulation accurately. This paper discusses the present status and developments tendency in simulating the space radiation environment, developing laboratory simulation equipments, measuring radiation field, researching radiation effects and mechanism, estimating and testing radiation effects, hardening electronics devices, etc. Furthermore, the key and basic problems in this field were discussed. The corresponding advices of space radiation physics and application were proposed.

The radiation dose from galactic cosmic rays during a manned mission to Mars is expected to be comparable to the allowable limit for space shuttle astronauts. Most of this dose would be due to galactic cosmic rays with energies < 1 GeV nucleon−1, with important contributions from heavy nuclei in spite of their low abundance relative to H and He. Using instruments on NASA's Advanced Composition Explorer (ACE) spacecraft, we have made the most statistically precise measurements to date of the solar minimum energy spectra of cosmic ray nuclei with charge Z = 4–28 in the energy range ∼ 40–500 MeV nucleon−1. We compare these measurements obtained during the 1997–1998 solar minimum period with measurements from previous solar minima and with models of the near‐Earth radiation environment currently used to perform shielding and dose calculations. We find that the cosmic ray heavy‐element spectra measured by ACE are as much as 20% higher than previously published solar minimum measurements. We also find significant differences between the ACE measurements and the predictions of available models of the near‐Earth radiation environment, suggesting that these models need revision. We describe a cosmic ray interstellar propagation and solar modulation model that provides an improved fit to the ACE measurements compared to radiation environment models currently in use.