The Radiation Assessment Detector (RAD) on the Curiosity rover has been characterizing the Martian surface radiation field since 2012. The dose observed by RAD is influenced by a variety of factors, including an essential one, the terrain. After parking near Murray Buttes in September 2016 where it first detected a similar to 5% decrease in dose rate, the rover has passed a series of other interesting terrains where we find decreases in the dose rate reaching 19%. This radiation reduction is due to extra shielding provided by the nearby surface structure, confirming the potential use of surface structures for radiation protection of humans on Mars. Combining a zenith-angle-dependent radiation model and the rover panoramic visibility map we calculate the downward radiation dose that RAD should observe under different topographic shielding conditions. This allows us to further evaluate the terrain-generated albedo dose at different locations. We finally estimate that on a flat surface the albedo radiation is between similar to 18% and 24% of the total surface dose. This study contributes to developing a realistic terrain-based radiation map which is important for future Mars explorers.

On 9 October 2024, a major Solar Energetic Particle (SEP) event was detected simultaneously across a wide range of heliolongitudes and heliocentric distances. Signatures were observed by Solar Orbiter, Parker Solar Probe (PSP), STEREO-A, near-Earth spacecraft (SOHO, GOES, ACE), and surface instruments on Mars (MSL/RAD). The event originated from an X1.8 solar flare in Active Region (AR) 3848, which produced a fast, Earth-directed full-halo coronal mass ejection (CME). This study aims to characterize the acceleration and heliospheric distribution of SEPs during this event and to evaluate its implications for space weather forecasting and radiation risks for future human exploration of Mars. We combined imaging and in situ particle observations from multiple spacecraft positioned at different longitudes and heliocentric distances. Analyses included flare and CME timing, SEP fluxes, onset times, and energy spectra at each vantage point. Multi-point comparisons allowed us to assess how CME-driven shocks accelerate and transport SEPs, and how cross-field propagation and interplanetary scattering shaped the observed particle distributions, particularly at Mars.The X1.8 flare began at 01:25 UTC, peaked at 01:56 UTC, and ended at 02:43 UTC. The associated full-halo CME was first detected by LASCO at 02:12 UTC from ~N13 W08, with speeds estimated at ~1,500 km/s (leading edge) and ~2,100 km/s (shock front). The CME arrived at Earth around 10 October 14:45 UTC. Solar proton intensities began rising at 02:40 UTC and reached S2 (moderate) radiation storm levels by 07:30 UTC. Widespread SEP detections, including at Mars, demonstrate efficient particle acceleration over an exceptionally broad spatial domain and highlight the role of extended shock fronts, cross-field diffusion, and interplanetary turbulence in shaping SEP propagation. These results provide critical constraints for SEP transport models and underline the value of multi-point observations for advancing forecasting capabilities and mitigating radiation hazards in deep space missions.

Understanding the Martian soil water budget is crucial not only for in situ resource utilization in future human missions to Mars, but also for reconstructing the geological and climatic history of the planet, as well as to assess the potential of ancient or even present microbial life. Here, we present a methodology to study near-surface water using albedo protons, based on measurements from the Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL). With this approach, water can be investigated beneath dust layers at approximately 1-6 cm, representing a new observational depth range compared to existing methods. In combination with data from the Dynamic Albedo of Neutrons (DAN) experiment, also part of MSL, we show that MSL/RAD has so far been unable to resolve small variations in regolith water of 2%-7%. However, supporting simulations suggest that larger water reservoirs, such as those at higher latitudes or locally near the equator, may be detected by MSL/RAD with measurement times of approximately two to 3 months. We demonstrate that a future Mars detector, specifically redesigned to measure albedo protons, could detect changes in near-surface water content of about 20% within roughly 6-16 days, and variations exceeding 40% within only a few days, with statistical significance. We therefore propose including albedo proton measurements in future missions to Mars or other extraterrestrial bodies, as they represent a promising complement to existing methods for probing near-surface water.

The current interest in lunar exploration led by the Artemis program is pushing scientists to search for lunar water deposits directly on the surface of the Moon, using small robotic rovers. The Institute of Experimental and Applied Physics, Czech Technical University, Prague (IEAP CTU), is developing a miniature Timepix3-based detector called Neutron HardPix, which is capable of mapping water deposits using non-invasive detection of neutrons created underground by cosmic rays and thermalized by hydrogen. This neutron spectrometer measures count rate variations in thermal, epithermal and fast neutrons attributed to hydrogen abundance in the lunar subsurface, while monitoring cosmic radiation as a natural source of neutrons. Neutron HardPix is based on the miniature (<0.1 U, 130 g) radiation monitor HardPix, and has significant space heritage.

With preparations underway for extended-duration crewed deep space missions, the health risks of solar particle events (SPEs) to astronauts are becoming increasingly pertinent. To address this hazard, the AstroRad vest, a personal radiation shielding garment providing targeted organ protection, was tested during Artemis I. Two anthropomorphic female phantoms, equipped with internal and external passive and active dosimeters, were flown aboard the Orion spacecraft: one unshielded and the other wearing AstroRad. Inner Van Allen belt transit active dosimeter measurements were extrapolated to simulate SPE scenarios, predicting effective dose reductions of ∼60% for an August 1972-like SPE and nearly 40% for an October 1989-like SPE, varying slightly with anatomical model. Such reductions could spare astronauts the equivalent of up to 193 and 131 days of deep space radiation exposure, respectively. These findings demonstrate that wearable shielding such as AstroRad could serve as a vital element for safe and sustainable human deep space exploration.

The radiation environment in space and the related radiation exposure is seen as one of the main health detriments for human missions in and beyond low Earth orbit (LEO). In addition to national space agencies sending astronauts to space, the near future is likely to bring numerous commercial endeavours that will facilitate the access to space, and specifically to LEO, for a growing number of people. The components of the cosmic radiation forming the environment in LEO are the galactic cosmic radiation (GCR), inner and outer radiation belt particles and sporadic solar energetic particle events. The steady flux of energetic particles in the galactic cosmic radiation produces a chronic low-dose-rate exposure, which is heavily influenced by several factors including variations during the solar cycle, the Earth’s magnetic field and spacecraft shielding. Investigations of the GCR variations over the course of a solar cycle provide valuable data for exploration mission planning and for the determination of the radiation load received due to the GCR environment. The RAMIS (Radiation Measurement in Space) instrument onboard the DLR Eu:CROPIS satellite, named after its primary payload: Euglena and Combined Regenerative Organic-Food Production in Space, has been measuring the radiation environment in a sun-synchronous polar orbit at 500 km to 600 km altitude since December 2018 and has been providing data on the exposure from GCR, inner and outer radiation belt particles and during numerous solar energetic particle events. Measurements at high latitudes and low geomagnetic shielding provide information on the exposure outside the magnetosphere in near-Earth interplanetary space.

In addition to the omnipresent Galactic Cosmic Rays, sudden Solar Energetic Particle (SEP) events present considerable health hazards for manned space missions. These events not only contribute to an increased long‐term cancer risk, but can, in extreme cases, cause acute radiation syndromes. Forecasting their imminent occurrence could significantly reduce radiation exposure by warning astronauts to move to shelter. However, all currently available tools are primarily designed for the Earth or Earth‐Moon system, which limits their applicability to future Mars missions. To address this, we developed a nowcasting system for SEP events applicable in deep space and on the Martian surface, which serves as a reliable last‐resort backup when forecasts fail. The methodology of this system is based on dose rates measured by the Radiation Assessment Detector onboard the Mars Science Laboratory, which recorded 5 SEP events during the 7‐month flight to Mars and 17 since its landing on Mars on 6 August 2012. An SEP event is triggered, and an astronaut is warned as soon as dose rates exceed the omnipresent background level by at least 25%. This approach suggests that our system can provide astronauts with at least 30 min to avoid both peak radiation exposure and the majority of the cumulative dose from SEP events. Our nowcasting system is robust, easily implementable in real‐life scenarios, and achieves a near‐zero false alarm rate both in deep space and on the Martian surface.

Understanding the zenith angle dependence of the Martian surface radiation environment is crucial for planning future human exploration missions to Mars. In our previous research (Wimmer et al. 2015; Guo et al. 2021; Khaksarighiri et al. 2023) we extensively studied the zenith-angle dependence of the Martian surface radiation dose rate. Leveraging the same validated radiation model, calibrated with data from the Radiation Assessment Detector (RAD) on Mars, we calculated the flux of secondary downward particles reaching to the surface of Mars from various zenith angles resulting from the interaction of primary particles with the Martian atmosphere. These flux of secondary particles, coming from different zenith angles, can be integrated into a comprehensive topographic map of Mars, providing a detailed depiction of the global radiation landscape.The construction of this radiation map requires careful consideration of various factors, including atmospheric column density, local and large-scale topography offering potential shielding effects, and the input spectrum is affected by heliospheric modulation. Additionally, accounting for seasonal pressure cycles and daily atmospheric surface pressure due to thermal tides is essential. Our model specifically focused on the influence of zenith angle on atmospheric column depth and simulations tailored to the Gale Crater region, a region explored by the Curiosity rover. Applying this methodology allows us to create lookup tables of all secondary particles reaching the Martian surface from various zenith angles and evaluate the atmospheric impact. Employing these matrices alongside the incident spectrum enables the calculation of secondary particle flux from all zenith angles on the Martian surface.This method provides valuable insights into the fluctuations in radiation flux on Mars, facilitating thorough assessments of potential radiation hazards. Mission planners can leverage these data, obtaining vital information to identify secure landing areas and sheltered regions for astronauts on the Martian surface.

The radiation environment en route to and on Mars is dominated by sporadic Solar Energetic Particle (SEP) events and omnipresent Galactic Cosmic Rays (GCRs). Both pose significant health risks for future crewed Mars missions due to high radiation exposure, increasing the long-term cancer risk. In extreme cases, acute radiation syndromes (ARS) may occur during intense SEP events, particularly if astronauts are exposed to high-dose rates during extravehicular activities.Forecasting the occurrence and intensity of SEP events using tools such as ESPERTA, UMASEP, or REleASE is therefore crucial to provide astronauts with sufficient time to seek shelter. However, this task remains highly challenging due to the variability of SEP events, the diverse heliospheric configurations, limited data and instrumentation, as well as the complexity of prediction models. Moreover, these systems are specifically designed for the Earth or Earth-Moon system, making their applicability to Mars missions uncertain.To adress this, we present a nowcasting system for SEP events in deep space and on the Martian surface, which serves as a reliable last backup in cases where forecasts fail. Our system is developed based on dose rate measurements from the Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL) during its 7-month cruise to Mars and over 12 years of operation on the Martian surface. We demonstrate that our nowcasting system provides astronauts with sufficient time to avoid both the peak radiation exposure and the majority of the cumulative dose from SEPevents. Additionally, astronauts are informed when it is safe to leave the shelter, with total shelter durations varying from a few hours to several days depending on the specific event. Our system is easy feasible, implementable in real-life scenarios, and achieves a near-zero false alarm rate both indeep space and on the Martian surface, as verified using data from MSL/RAD.

The Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory's Curiosity rover is the first-ever instrument continuously monitoring energetic particles on the surface of Mars. Since the rover's landing on August 6, 2012, RAD has accumulated valuable data, providing an unprecedented opportunity to assess the radiation environment across a solar cycle on an another planet.Understanding the radiation environment on Mars is crucial for a more accurate assessment of the risks posed to manned future space missions. Moreover, it also serves to further investigate planetary conditions, properties of the Sun, and galactic cosmic rays (GCRs). The radiation field on the surface of Mars primarily consists of charged particles, including primary GCRs propagating to the Martian surface and secondary particles generated through the interaction of primary GCRs with the Martian atmosphere or soil. Furthermore, it undergoes temporal changes caused by factors such as atmospheric pressure variations due to thermal tides, seasonal changes, geographical and topographical shielding effects, heliospheric modulation of GCRs, as well as Martian soil and subsurface conditions. Considering all these factors is essential for a comprehensive description of the radiation environment. Here we utilize the extensive RAD dataset spanning the last 11 years to delve into the intricate variations in particle flux. Our analysis encompasses a diverse array of particle species, providing a comprehensive understanding of how particle flux evolves over the course of one complete solar cycle. This extended time frame allows us to capture and analyze long-term trends, offering valuable insights into the dynamic nature of particle interactions within the Martian environment. By exploring the temporal patterns of particle flux across different species, we aim to contribute to a more nuanced comprehension of the complex radiation dynamics on Mars and its implications for future space missions and potential habitation. Additionally, we endeavored to understand the impacts of subsurface composition on the Martian surface radiation field, particularly in generating additional upward particles. This investigation is significant as it contributes to the exploration of potential subsurface water content on the surface of Mars.

The topographic influence of the radiation environment on the Martian surface radiation is crucial for future human exploration. Topographic maps help assess radiation flux variations, aiding in hazard evaluation. Creating a global radiation map requires accounting for seasonally varying atmospheric density, heliospheric modulation, and topography. Here, we use a radiation model to derive the flux of secondary downward particles generated by the interaction of primary protons with the Martian atmosphere. Our model examines two key factors: (a) the dependence of atmospheric column depth on the zenith angle, affecting radiation directionality as horizon-arriving particles traverse more atmosphere than vertical ones and (b) atmospheric conditions at surface heights in Gale Crater, crucial for developing radiation dose maps that incorporate topographic effects. Our model is validated against Radiation Assessment Detector measurements and benchmarked with existing models. We construct response matrices representing the ratio of secondary particles at the Martian surface to primary inputs across zenith angles, assessing atmospheric effects. We combine these matrices with the incident spectrum to compute secondary particle fluxes from all zenith angles for Galactic Cosmic Rays and Solar Energetic Particles. These fluxes will be integrated into a topographic map of Mars in a follow-up study, providing a detailed representation of surface radiation levels across different terrains. This approach aids mission planners in identifying safe landing sites for astronauts.

Exposure to cosmic radiation is a major concern in space exploration. On the Martian surface, a complex radiation field is present, formed by a constant influx of galactic cosmic radiation and the secondary particles produced by their interaction with the planet's atmosphere and regolith. In this work, a Martian environment model was developed using MCNP6 following the guidelines of the 1st Mars Space Radiation Modeling Workshop. The accuracy of the model was tested by comparing particle spectra and dose rate results with other model results and measurements from the Radiation Assessment Detector (RAD) onboard the Curiosity rover, taken between November 15, 2015, and January 15, 2016. The ICRP's voxel-type computational phantoms were then implemented into the code. Organ dose and effective dose equivalent were assessed for the same time period. The viability of a mission on the surface of Mars for extended periods of time under the assumed conditions was here investigated.

The Near-Earth Space Radiation and Plasma Environment falls within the realm of G3 Cluster (G3 refers to ‘Near-Earth Radiation and Plasma Environment’ of the ‘Coupled Geospace System’) under the COSPAR (Committee On Space Research) /International Space Weather Action Teams (ISWAT) Initiative. The diverse and dynamic particle populations from this region pose challenges from both science and space weather-impact perspectives. The G3 cluster has intimate connections with solar, heliosphere clusters, and the other Geospace ones (G1, G2) through a chain of physical processes. This paper reviews recent scientific advances in understanding this complex space environment, identifies gaps in research and space weather applications, and maps out our recommendations on priorities for the next 5-10 years.

Space radiation is a notable hazard for long-duration human spaceflight1. Associated risks include cancer, cataracts, degenerative diseases2 and tissue reactions from large, acute exposures3. Space radiation originates from diverse sources, including galactic cosmic rays4, trapped-particle (Van Allen) belts5 and solar-particle events6. Previous radiation data are from the International Space Station and the Space Shuttle in low-Earth orbit protected by heavy shielding and Earth's magnetic field7,8 and lightly shielded interplanetary robotic probes such as Mars Science Laboratory and Lunar Reconnaissance Orbiter9,10. Limited data from the Apollo missions11-13 and ground measurements with substantial caveats are also available14. Here we report radiation measurements from the heavily shielded Orion spacecraft on the uncrewed Artemis I lunar mission. At differing shielding locations inside the vehicle, a fourfold difference in dose rates was observed during proton-belt passes that are similar to large, reference solar-particle events. Interplanetary cosmic-ray dose equivalent rates in Orion were as much as 60% lower than previous observations9. Furthermore, a change in orientation of the spacecraft during the proton-belt transit resulted in a reduction of radiation dose rates of around 50%. These measurements validate the Orion for future crewed exploration and inform future human spaceflight mission design.

In the MARE experiment onboard the NASA Artemis 1 mission of the ORION spacecraft to lunar orbit, two anthropomorphic female phantoms, equipped with a large number of active and passive radiation detectors were flown. Among the detectors were both LiF:Mg,Ti and LiF:Mg,Cu,P TL detectors as well as Al2O3:C 2 O 3 :C OSL detectors. In order to correctly interpret the measured doses, the effective relative TL/OSL efficiency for cosmic radiation of these detectors was calculated by combining simulated radiation spectra for the cis-lunar space conditions with the efficiency functions based on experimental data for different ions and on a microdosimetric model. The obtained results show that for the ORION shielding conditions, the relative efficiency of LiF:Mg,Ti is close to unity (0.95), while the remaining detectors show somewhat smaller efficiency: 0.90 for Al2O3:C 2 O 3 :C and (0.81-0.86) for LiF:Mg,Cu,P. The analysis of the influence of the shielding thickness on the relative TL/OSL efficiency revealed, that for low shielding conditions, the relative efficiency may be more significantly decreased, reaching values between 0.71 (LiF:Mg,Cu,P) and 0.85 (LiF:Mg,Ti) for 1 g/cm2. 2 .

An illustrative sample mission of a Mars swing-by mission lasting one calendar year was chosen to highlight the application of European risk assessment software to cancer (all solid cancer plus leukaemia) risks from radiation exposures in space quantified with organ dose equivalent rates from model calculations based on the quantity Radiation Attributed Decrease of Survival (RADS). The relevant dose equivalent to the colon for radiation exposures from this Mars swing-by mission were found to vary between 198 and 482 mSv. These doses depend on sex and the two other factors investigated here of: solar activity phase (maximum or minimum); and the choice of space radiation quality factor used in the calculations of dose equivalent. Such doses received at typical astronaut ages around 40 years old will result in: the probability of surviving until retirement age (65 years) being reduced by a range from 0.38% (95%CI: 0.29; 0.49) to 1.29% (95%CI: 1.06; 1.56); and the probability of surviving cancer free until retirement age being reduced by a range from 0.78% (95%CI: 0.59; 0.99) to 2.63% (95%CI: 2.16; 3.18). As expected from the features of the models applied to quantify the general dosimetric and radiation epidemiology parameters, the cancer incidence risks in terms of surviving cancer free, are higher than the cancer mortality risks in terms of surviving, the risks for females are higher than for males, and the risks at solar minimum are higher than at solar maximum.

In May 2024 the strongest geomagnetic storm since the Halloween storms of 2003 occurred. Media reported worldwide about the space weather situation and its effects on the infrastructure. Of particular interest were reports claiming severe effects on the radiation exposure at aviation altitudes, although no data supporting this assertion were available at that time. In this work the different aspects that affect the radiation exposure at aviation altitudes are discussed for the event. Furthermore, the corresponding dose rates are evaluated and compared to data from Low Earth Orbit. Model calculations indicate an additional contribution to the radiation field at aviation altitudes due to this extraordinary space weather situation, although the dose rates were still in the lowest category D0 of the space weather D-index, i.e., within the dose rate variation of a solar cycle.

AbstractThe Moon will be a primary target for human space exploration in the near future. A limiting factor for a crewed mission to the Moon is the radiation dose during their stay on the lunar surface. While the total dose is expected to be dominated by the galactic cosmic radiation (GCR), the potential occurrence of large solar energetic particle events may lead to severe short‐term effects and endanger the success of the mission. This work investigated the expected dose rates for maximum GCR intensity and the total dose from several historical solar energetic particle events, including the NASA reference event, through the application of numerical simulations with the Geant4 Monte‐Carlo framework. An evaluation of the shielding effect of lunar regolith was carried out. For the solar particle events a shielding of more than 4 g/cm2 of regolith would reduce the expected dose to below the current 30‐day limits and a shielding of more than 10 g/cm2 would result in a safety margin factor of two. For GCR adding additional mass shielding did not reduce the absorbed dose significantly. The estimated total dose equivalent received utilizing around 180 g/cm2 of regolith amounted to 200 mSv/year, which is only about 25% below the corresponding estimates for an unshielded environment. The comparison to model and experimental data from literature showed reasonable agreement to measurements but the analysis of various earlier model results revealed, that substantial differences between the models exist, despite all improvements that have been achieved in recent years.

The South Atlantic Anomaly (SAA) is a geographical region over the South Atlantic Ocean where the inner Van Allen radiation belt extends down particularly close to Earth. This leads to highly increased levels of ionizing radiation and related impacts on spacecraft in Low Earth Orbits, e.g., correspondingly increased radiation exposure of astronauts and electronic components on the International Space Station. According to an urban legend, the SAA is also supposed to affect the radiation field in the atmosphere even down to the altitudes of civil aviation. In order to identify and quantify any additional contributions to the omnipresent radiation exposure due to the Galactic Cosmic Radiation at flight altitudes, comprehensive measurements were performed crossing the geographical region of the SAA at an altitude of 13 km in a unique flight mission—Atlantic Kiss. No indication of increased radiation exposure was found.