It is known that the distribution of neutrons over the Martian surface depends substantially on the presence of subsurface water ice or hydrated minerals, and the thickness of the Martian atmosphere experiencing seasonal variations. The observed variations of neutron flux could be converted to the neutron dose on the Martian surface. This is an important parameter needed to be known to plan future human expeditions to Mars. This paper presents numerical simulations of Martian neutron flux which have been conducted to create a global surface map of neutron effective dose equivalent rate and to understand its regional variability and evolution with Martian seasons. It is shown that within the 50N-50S latitude range, proposed as preferable one for the landing of manned missions, the neutron effective dose equivalent rate varies within 85-145 mu Sv/day. The existing list of the most suitable Regions of Interests (ROI), where humans could land, live and work, has also been considered. To mitigate the risk of neutron radiation environment, it has been concluded that the landing site selection shall prioritize highlands with elevated concentration of subsurface water over dry lowlands/valleys. The main analysis addresses the maximum flux of Galactic Cosmic Rays (GCR) or solar minimum, but additional numerical calculations have shown that neutron dose gradually decreases twofold at the minimum flux of GCR or solar maximum. This dependence could be used to renormalize neutron effective dose equivalent rate to any phase of the solar cycle.

This paper presents the observational findings for the most powerful solar particle event (SPE) on Mars in the current 25th solar cycle, based on surface (DAN/Curiosity) and orbital (HEND/Mars Odyssey) measurements. The numerical modelling of SPE proton interaction with the atmosphere and Martian surface showed that the computational results are in good agreement with the experimental data. The neutron component of the radiation background in orbit and on the surface was evaluated near the SPE maximum. The integral neutron dose on the Martian surface during the entire SPE was estimated as 600 mu Sv, which equals the dose received during similar to 11 days in quiet Sun environment. The obtained data were extrapolated to more powerful solar events known from the history of observation. The Carrington event was used as an example. For such a hypothetical SPE, the total neutron dose may achieve as high as 240 mSv. It is 1.6 times higher than annual dose limit allowed for astronauts in the NASA ORION project.

The dosimeter Liulin-MO for measuring the radiation environment on board the ExoMars Trace Gas Orbiter (TGO) is a module in the Fine Resolution Epithermal Neutron Detector (FREND). A number of solar energetic particle (SEP) events were observed in Mars orbit from July 2021 to 2024 during the increasing phase and close to the maximum of the 25th solar cycle activity. The results from the SEPs measurements obtained in 2021-2023 by Liulin-MO have been previously reported. Here we present the LiulinMO results from the observation of the radiation parameters of the SEP events during January- October 2024. The most powerful SEP event registered up to now in TGO orbit started on 20 May 2024. The maximum dose rate during this SEP event has been 2800 f 280 mu Gy h-1 and the maximum particle flux - 383 f 19 cm-2 s-1. The total event lasted for about 64 hours up to 24 May with a long tail of increased dose rates and fluxes. The total dose from SEPs for the 64 hours of the main phase of the SEP event was 24.7 f 2.5 mGy. The total dose from SEPs during this event is equal to the dose from the galactic cosmic rays (GCR) received for about 200 days at this phase of solar cycle 25. The total dose from all SEPs during January - September 2024 is 36.6 mGy (in Si), which is approximately equal to the dose received from GCR for the same period. The observations of SEPs in Mars orbit are compared to the observations during the same periods of proton fluxes measured by the GOES satellite in Earth orbit. The results show that some of the SEPs observed in Mars orbit, excluding the biggest SEP events of 20-24 May and 05-07 September, are also seen in the GOES proton fluxes data. SEP events recorded both in Mars and Earth orbits are related to coronal mass ejections (CMEs) observed by the SOHO and STEREO A coronagraphs. The paper shows that responsible for most of the SEP events registered both in the Liulin-MO data and in the GOES proton fluxes data are halo CMEs. The paper also shows that the sources of the three most powerful SEP events in Mars orbit - those of 20 May, 23 July and 05 September - are halo CMEs from the far side of the Sun. Some of these CMEs are associated with major X class far-side flares. Long-term investigations of the GCRs radiation parameters in Mars orbit show that in August 2024 (the last month of our data with no recorded SEP events) the dose rate was 6.5 f 0.65 mu Gy h-1 and the particle flux - 1.4 f 0.07 cm-2 s-1. These values are about 40 % of the corresponding maximal values measured by Liulin-MO during the solar cycle 24 minimum in March 2020. The above results show the importance of long-term measurements (at least during a full solar cycle) of the radiation conditions in Mars vicinity. Such measurements will make it possible to obtain the data necessary for the planning of future manned and robotic missions, as well as for the selection of the best time interval in the solar cycle for a manned flight to the planet.

Abstract We modeled (sub-)surface temperatures for the upper two-meter regolith layer near the lunar poles. The temperature maps are compared to the observed hydrogen signal from the Lunar Enhanced Neutron Detector (LEND). We focused our study on six Neutron Suppression Regions (NSRs). Introduction The lunar poles offer a thermal environment with surface temperatures allowing for water ice to accumulate, especially in Permanently Shadowed Regions (PSRs) commonly found at crater floors [1]. Extensive remote sensing and modeling techniques were applied from a series of missions to detect and quantify potential deposits (e.g. [2][3]). Although plausible evidence was found from orbiting spacecrafts, alternative explanations are still possible, e.g. roughness, fresh surface material, hydroxyl (OH) bearing minerals etc. However, the Lunar Crater Observation and Sensing Satellite (LCROSS) found direct evidence of water through impacting within the PSR of Cabeus crater. LEND [4] observations revealed several NSRs [5], i.e. hydrogen-rich areas which are typically found within PSRs. However, some NSRs are occasionally in sunlight creating surface temperatures at which water ice cannot be stable. At specific thermal conditions, i.e. maximum and average temperatures are 120 K and 105 K respectively, an ice pumping mechanism into the sub-surface is activated [6]. We investigate to which extent temperatures correlate with LEND’s hydrogen signal and whether or not ice pumping can explain the existence of some of the NSRs. Data and Method Our study is based on polar 650x650 km Lunar Orbiter Laser Altimeter (LOLA) Digital Terrain Models (DTMs) [7][8]. Lunar (sub-)surface temperatures are modeled by solving the 1D heat equation [9]. We treat the Sun as an extended source considering the limb-darkening effect. Heat conduction is modeled within the upper two meters of regolith and temperatures are derived for 30 layers. Multiple scattering and re-radiation of VIS and IR is evaluated at each pixel from a 50x50 km window. Earth-shine (VIS and IR) and a constant radiogenic heat source of 0.016 W/m² are also incorporated in the model. The DTMs were synthetically illuminated [10] in 12-h time steps for a 19-year period, 01-01-1991 to 01-01-2010. Since similar illumination conditions occur at the start and end time we could iterate the process until temperatures converged. After 5 iterations (i.e. 95 years) we found an equilibrated solution from which we derived results presented in this study. Our investigated NSRs are: areas near Whipple, Fibiger and Peary at the north pole and areas inside Shoemaker, Haworth and Cabeus crater at the south pole. For each NSR we derived minimum, average and maximum temperature maps. Additionally, maps of suppression parameter ξ were prepared. The suppression parameter represents the ratio between the average neutron counting within LEND’s field-of-view to the average neutron counting of a hydrogen-poor reference area [5]. 3. Results To determine whether or not temperature and suppression parameter maps correlate we needed to set thresholds. For instance, the threshold for temperature below which we assume water ice to be stable is 110 K [11]. The threshold for the suppression parameter ξ was set to 0.83. We found this threshold by evaluating the observed ξ around the LCROSS impact site for which we know that water ice is present. At each depth layer we compared the overlap of the two emerging areas of potential water ice, one determined by temperature and the other determined by ξ (see Fig. 1). We also derived growth rates (%/cm) indicating whether significant increase in overlap (%) is achieved by comparing ξ to temperature layers in greater depth (cm). For the south polar NSRs we find that both areas overlap > 95% and ice appears to be present within the upper 19 cm of regolith. The north polar NSRs show an overlap of ~50-70% and ice seems to be buried to greater depths, e.g. 65 cm. In fact, we found that maximum and average temperatures create ideal conditions for ice pumping into the sub-surface. 4. Discussion Our south polar NSRs reside in PSRs, i.e. the coldest areas on the Moon. They follow the classical view on how water ice deposits at the poles: water molecules hop over the lunar surface and eventually get trapped and accumulate in PSRs. Our selected north polar NSRs, however, reside in non-PSR areas which are occasionally in sunlight and are generally too warm for water ice to be stable. Ice pumping seems to be the explanation for those locations. We could show that NSRs and modeled temperatures do correlate, either at surface or sub-surface level.

The ExoMars landing mission, which is currently scheduled to launch in 2022, will carry the active gamma ray and neutron spectrometer ADRON-EM and compact passive neutron spectrometer ADRON-RM to the equatorial region of Mars as part of the mission's science payload. The main science objective of the ExoMars mission is dedicated to understanding the evolution and habitability of Mars.ADRON-EM instrument is developed in Space Research Institute (IKI) for active neutron sensing of the soil from the stationary landing platform. The main goal of this experiment is study of elemental composition of the martian subsurface down to 1 m. The instrument consists of two units, the block of detectors and electronics (DE) and the pulse neutron generator (PNG). Measuring post-pulse neutron and gamma ray emission from the soil, one can detect layering stratification of hydrogen and other major elements of the soil.The second complementary instrument ADRON-RM (IKI) is installed on the Rover. It will measure the spatial variability of neutron flux emitted from the martian surface along the traverse. The data processing will convert the raw data into an estimation of bulk water distribution and abundance of neutron absorbing elements, mainly chlorine and iron. The instrument will also provide continuous monitoring of the neutron component of the radiation background on the surface which is necessary to know for planning future human missions to the planet.In the beginning of the surface mission after landing, there is the unique possibility to perform the measurement of subsurface density by both instruments operating together. The data for this analysis will be obtained from different distances between rover and landing platform.Description of ADRON-EM and RM instruments and expected results will be presented.

Fine Resolution Epithermal Neutron Detector (FREND) is an instrument onboard ExoMars' Trace Gas Orbiter. Its measurements of epithermal neutron flux on orbit provide data on hydrogen (and thus, water) content in the 1-m thick near-surface regolith layer. Similar experiments have been performed before, neutron sounding is a well-established technique for estimating water content in the celesital body's soil. FREND's chatacteristic feature is its collimator - a massive body surrounding detectors and narrowing their field of view substantially, thus providing for very high spatial resolution, around 60 to 200 km, depending on measurement conditions. Such spatial resolution allows identifying local water-rich features with relief and other geomorphological features, assess water content in small ellipses of future landing sites.In this study we present latest findings based on FREND data, containing a number of surprisingly "wet" local features in the equatorial band. Water or water ice is not stable at the surface of Mars, in the equatorial regions especially, that is why locating areas with enhanced subsurface hydrogen or water is of much interest both to scientists and for the purpose of planning future exploration missions.

The lunar surface in the vicinity of the poles has special properties compared to the surface at the equator and at moderate latitudes. First, the polar regolith contains quite a large amount of water ice, which significantly affects the neutron radiation generated under the influence of galactic cosmic rays. Second, the temperature of the polar regolith can have extremely low values of about 25 K, as a result of which the thermal component of the neutron flux is partially held in the gravitational field. Based on numerical modeling of neutron radiation from the lunar surface, its main features were shown for the polar regions compared to the equatorial ones: a significant decrease in the ratio of epithermal and thermal neutron fluxes due to an increase in the concentration of hydrogen in the regolith, as well as a significant increase in the density of thermal neutrons near the surface due to gravitational capture.

The article provides a description of the crater in the marginal zone of the southern polar region of the Moon with the coordinates of the center 126.59° W, 64.32° S The diameter of the crater is 34 km. It has a fractured bottom, which is considered a sign of magma intrusion into the subcrater space. The absolute age of formation of the crater under study was estimated to be 3.85 billion years based on the spatial density of small craters superimposed on its rim. In the vicinity of the studied crater, low-iron anorthosite material is predominant. It can be argued that the basin of the crater under study is very dry compared to its surroundings. A significant loss of hydrogen/water and its redistribution from the bottom of the crater to the area around the crater could be caused by reworking of the surface due to the intrusion of magma under the crater, traces of which can be traced by the presence of cracks on the bottom of the crater.

The Mercurian Gamma-ray and Neutron Spectrometer (MGNS) is a scientific instrument developed to study the elementary composition of the Mercury’s sub-surface by measurements of neutron and gamma-ray emission of the planet. MGNS measures neutron fluxes in a wide energy range from thermal energy up to 10 MeV and gamma-rays in the energy range of 300 keV up to 10 MeV with the energy resolution of 5% FWHM at 662 keV and of 2% at 8 MeV. The innovative crystal of CeBr3 is used for getting such a good energy resolution for a scintillation detector of gamma-rays.During the BC long cruise to Mercury, it is planned that the MGNS instrument will operate practically continuously to perform measurements of neutrons and gamma-ray fluxes for achieving two main goals of investigations.The first goal is monitoring of the local radiation background of the prompt spacecraft emission due to bombardment by energetic particles of Galactic Cosmic Rays. This data will be taken into account at the mapping phase of the mission on the orbit around Mercury. Detailed knowledge of the spacecraft background radiation during the cruise will help to derive the data for neutron and gamma-ray emission of the planet at the mapping stage of the mission because many elements, like Mg, Na, O and others, the abundance of which at the uppermost layer of the planet is studied, are also present in the material of the spacecraft. Indeed, the nuclear lines of Al, Mg and O are well-pronounced in the spectrum, which are also expected to be detectable in the gamma-ray spectrum of the Mercury emission.The second goal of MGNS cruise operations is the participation in the Inter Planetary Network (IPN) program for the localization of sources of Gamma-Ray Bursts in the sky. In fact, the localization accuracy by the interplanetary triangulation technique is inversely proportional to the distance between the spacecrafts that jointly detected a GRB. Before the launch of BepiColombo, the IPN network included a group of spacecrafts in the near-to-Earth orbit (e.g. Konus-Wind, Fermi-GBM, INTEGRAL, Insight-HXMT) and the Mars Odyssey spacecraft on the orbit around Mars. Now, MGNS provides another interplanetary location, potentially increasing the accuracy of GRBs localization. During the first 13 months of continuous operation, MGNS detected 24 GRB's. Pre-set value of time resolution for continuous measurements of profiles of GRBs is 20 seconds. Since of November 14, 2019, the BC Mission Operation Centre has allocated downlink resources to run MGNS continuously in a 1 sec time resolution for GRB measurements. The GRB detection rate, based on data with a time resolution of 1 sec is about 2-3 GRB's per month.Gamma-rays of solar flares are also detectable by MGNS. Solar flares are nonstationary and anisotropic processes and the ability to observe them from different directions in the Solar system is crucial for further understanding their developments and propagation, as it was demonstrated in the case of HEND instrument on board Mars Odyssey. The Sun cycle is presently around its minimum, and MGNS has not detected any solar events during its first 7 months of the cruise, but the flight to Mercury is long enough and many future flares are expected to be detected.The MGNS instrument will also perform special sessions of measurements during flybys of Earth, Venus and Mercury with the objective to measure neutron and gamma-ray albedo of the upper atmosphere of Earth and Venus and of the surface of Mercury. Another objective is to test the computational model of the local background of the spacecraft using the data measured at different orbital phases of flyby trajectories. The low altitude flybys (such as the 700 km flyby for Venus and three 200 km flybys for Mercury) would be the most useful for such tests being BC maximally shadowed for cosmic radiation by the actual planet. Neutron and gamma-ray measurements during Earth flybys enable investigation of interaction between solar wind and Earth environments as well as studies of spacecraft neutron and gamma-ray background upon its passage through the Earth's radiation belts.

This paper is Part II of a double-paper series that presents the abundance of water and chlorine along with other neutron-absorbing elements in the shallow subsurface of Gale crater based on measurements by the Dynamic Albedo of Neutron (DAN) instrument onboard NASA's Curiosity rover. Initial results were represented as pixels on map data products from both DAN active and passive measurements made along the 27-km traverse of the rover, corresponding to the mission period from landing on the martian surface in August 2012 through December 2021. In Part II, the contents of water and chlorine along with other neutron absorbers are studied separately for distinct geological regions along the traverse. Mean values and sample variances of these values are presented for each region. Water-equivalent hydrogen (WEH) measurements show variability within the Jura member of the Murray formation and increase within the Carolyn Shoemaker formation. A large fraction of stratigraphic units (e.g., Bradbury, Sheepbed, Pahrump Hills and others) have mean WEH values between 2 and 3 wt.%, while units in the second part of the traverse (Jura, Knockfarrill Hill, Glasgow, Pontours) have mean values of WEH above 3 wt.%. The mean absorption-equivalent chlorine value has no large variations for all tested geologic units; it is equal to around 1% for all of them. The Dynamic Albedo of Neutrons instrument installed on NASA's Curiosity rover provides measurements of hydrogen (as an indicator of water) and other neutron-absorbing elements (primarily chlorine) in the shallow subsurface of Gale crater on Mars. The initial data set for this study consists of pixel data products obtained from the instrument measurements taken over the rover's traverse of 27 km from August 2012 to December 2021. The data has been analyzed for distinct geological members defined by the Mars Science Laboratory team, allowing independent examination of various geological locations. The Jura, Knockfarrill Hill, and Pontours members exhibit mean water estimation values above 3 wt.%, while the majority of stratigraphic units, such as Bradbury and Sheepbed, have mean water values ranging between 2 and 3 wt.%. Measurements of water reveal differentiation in the Jura member of the Murray formation. The highest water values, reaching up to 4 wt.%, are observed in locations of the Carolyn Shoemaker formation. For other neutron-absorbing elements, the mean value is roughly 1 wt.% for all geological units tested and does not vary significantly. The Dynamic Albedo of Neutron (DAN) data was analyzed for the period of time from August 2012 to December 2021, for almost 27 km of the MSL traverse 15 distinct MSL geological regions were examined using the DAN data The DAN data recognized the presence of two subregions within the Jura member of the Murray formation based on Water-equivalent hydrogen concentration

The article presents the results of the analysis of data from the Russian neutron spectrometer LEND (Lunar Exploration Neutron Detector), installed aboard NASA’s lunar orbiter LRO (Lunar Reconnaissance Orbiter). An estimate of the content of subsurface water ice in the permanently shadowed region Cabeus-1, located inside the large Cabeus crater in the vicinity of the lunar south pole, has been obtained. The analysis used observations made with the LEND instrument from 2009 to 2023. It is shown that the surface neutron albedo in the vicinity and inside of Cabeus-1 correlates with the relief height and the distribution of average annual temperatures. The average subsurface water ice content over the entire Cabeus-1 region was estimated to be 0.49 ± 0.05

Remote neutron sensing onboard martian rovers is an advanced technique in planetary science. Such measurements provide investigations on hydrogen abundances and elements with high thermal neutron absorption cross sections down to ~60 cm of subsurface [1]. The presence of hydrogen (mostly water/ice) in subsurface significantly influences the neutron leakage spectrum due moderation and thermalization through collisions with hydrogen nuclei. As a result, the variations of neutron flux detected onboard in different energy bands correlate with subsurface hydrogen/water abundance. Dynamic Albedo of Neutrons (DAN) is the first neutron spectrometer installed on the NASA’s rover [2]. More than 7 years, NASA rover is successfully traversing across Mars surface exploring Gale crater. Adron-RM is the next generation neutron spectrometer, which is a part of the ExoMars 2022 rover payload [3]. This work will present scientific potential of remote neutron technique to distinguish local features in martian subsurface, based on DAN findings. In addition, we will provide Adron-RM measurement schematic and scientific potential on investigations in the area of the ExoMars 2022 landing site. References[1] Nikiforov, S. Y., et al., (2020). Assessment of water content in martian subsurface along the traverse of the Curiosity rover based on passive measurements of the DAN instrument. Icarus, 346, 113818. https://doi.org/10.1016/j.icarus.2020.113818[2] Mitrofanov, I. G., et al., (2012). Dynamic Albedo of Neutrons (DAN) experiment onboard NASA’s Mars Science Laboratory. Space Science Reviews, 170(1–4), 559–582. https://doi.org/10.1007/s11214-012-9924-y[3] Mitrofanov, I. G., et al., (2017). The ADRON-RM Instrument Onboard the ExoMars Rover. Astrobiology, 17(6–7), 585–594. https://doi.org/10.1089/ast.2016.15

The neutron emission of Mars is known to be produced due to the bombardment of Martian surface by Galactic Cosmic Rays (GCRs). As evidenced by numerical simulation, the intensity of neutron emission on the planetary surface is much larger than that of the neutron emission at the orbital altitude due to multiple reflections of the neutrons emitted from soil by the atmosphere. The code developed for simulations was validated using the experimental data of neutron emission acquired in the Gale crater by the RAD and DAN instruments aboard the NASA's Curiosity rover. Neutron emission was simulated for two Martian areas: the dry Solis Planum territory and the bottom of the Valles Marineris system of canyons, which is thought to be the most wet equatorial spot on Mars. For both areas a strong effect is found, showing a considerable difference between the neutron emission on the surface and at the altitude of a typical orbit. It was also shown that surface emission in these two areas is quite different due to the difference of mass fraction of water in the shallow subsurface. Finally, the seasonal variations of neutron emission in these areas due to the atmospheric seasonal changes are also estimated.

Introduction: The Dynamic Albedo of Neutrons (DAN) instrument designed to detect neutrons in order to determine hydrogen abundance in the Martian subsurface (down to 1 m deep) [1,2] is successfully working onboard Mars Science Laboratory (MSL) rover Curiosity for more than 7 years. We investigate the possible correlation between Water Equivalent Hydrogen (WEH) value as measured by DAN instrument along the Curiosity traverse and the presence of hydrated/hydroxylated minerals as seen by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument onboard Mars Reconnaissance Orbiter (MRO) in order to connect geochemical features of the surface to the subsurface WEH measurements.The Curiosity rover covered more than 20 km on the Martian surface and crossed a range of terrain types and geological structures of different mineralogical composition. For the last 2 years Curiosity is driving across the regions discovered from the orbit by their spectral features: Vera Rubin ridge, rich in hematite, and Glen Torridon, containing clay minerals, according to CRISM data. We present the results of the comparison between CRISM data and DAN measurements acquired for these two regions.Fig. 1. DAN active measurements for Vera Rubin ridge and Glen Torridon. Data from sol 1800 up to sol 2470. Instrumentation: DAN instrument operates in two modes: active and passive. In active mode, DAN detects neutrons from the pulsing neutron generator (PNG). In passive mode, the instrument detects low energy neutrons produced by the rover’s Multi-Mission Radioisotope Thermoelectric Generator and by galactic cosmic rays as they propagate through Martian atmosphere and penetrate Martian subsurface. These neutrons interact with the soil nuclei through both elastic and inelastic scattering, slow down, and escape from the surface to be measured by DAN instrument. The energy spectrum of these neutrons is dependent on the amount of hydrogen in the Martian subsurface.CRISM instrument onboard MRO is an imaging spectrometer that can cover wavelengths from 362 to 3920 nanometers at 6.55 nanometers per channel, observing Mars in both visible range and wavelengths within the infrared range [3]. Imaging the Martian surface in these wavelength ranges CRISM can identify a range of minerals by their spectral signatures.Data Analysis: WEH value obtained through the analysis of DAN active measurements (see Fig. 1) increases from the mean value of 2.7 wt.% for Vera Rubin ridge up to 3.7 wt.% for Glen Torridon. Similarly, WEH value derived from the passive measurements (see Fig. 2) increases from 3.0 wt.% to 3.8 wt.%, respectively [4].Fig. 2. DAN passive measurements for Vera Rubin ridge and Glen Torridon [4]. The correlation with mineralogical composition of the Martian surface was based on ALT and HYD Specialized Browse Product Mosaics, provided by the CRISM Team for the purpose of MSL landing site mapping [5]. The composite of the mosaics constructed from the IR spectral range show a combination of the indicators of hydrated/hydroxylated minerals believed to be present at Gale crater.To find the correlation between DAN passive data and CRISM products we spatially overlayed the two datasets. Thus, the four samples of DAN passive data were obtained: passive measurements spatially corre-sponding to hydrated/hydroxylated minerals in CRISM products: phyllosilicates, mono- and polyhydrated sulfates, and passive measurements with no such corre-spondence. Then we compared three WEH distributions for each type of minerals with the reference one.Fig. 3. WEH value distribution for: the group of DAN measurements with the spectral signature of polyhydrated sulfates – for Vera Rubin ridge and Glen Torridon (blue) and the reference group of the DAN measurements which do not have signatures of hydrated minerals – for the whole traverse (black) Dotted lines indicate mean values of the distributions: 3.24 wt.% and 2.56 wt.%, respectively. Results. We present the results for Vera Rubin ridge and Glen Torridon parts of the Curiosity traverse. The analysis shows that not only polyhydrated sulfates (see Fig. 3) on the surface can lead to the WEH value increase, as it was stated in [6], but phyllosilicates (see Fig. 4) can provide the same effect, possibly if being presented not only on the surface and detected by CRISM, but in sufficient amounts in the subsurface to be detected by DAN. The shift of the WEH distribution, corresponding to the phyllosilicates on the surface, as well as the probability of their coincidence (according to the Pearson criterion – almost zero), allows us to presume a pronounced thickness of the phyllosilicates layer in the subsurface of Glen Torridon.Fig. 4. WEH value distribution for: the group of DAN measurements with the spectral signature of phyllosilicates – for Vera Rubin ridge and Glen Torridon (red) and the reference group of the DAN measurements which do not have signatures of hydrated minerals – for the whole traverse (black). Dotted lines indicate mean values of the distributions: 3.33 wt.% and 2.56 wt.%, respectively. References: [1] Mitrofanov I. G. et al. (2014) J. Geophys. Res., 119, 1579–1596. [2] Livak M. L. et al. (2014) J. Geophys. Res., 119, 1259–1275. [3] Pelkey, S. M., et al. (2007), , J. Geophys. Res., 112, E08S14. [4] Nikiforov S. Y. et al. (2020), LPSC2020, XXX. [5] Viviano-Beck, C. E., et al. (2014), J. Geophys. Res., 119, 1403–1431, http://crism.jhuapl.edu/ [6] Djachkova M. V., et al. (2019), EGU2019, id.16622

This study reports cataloged data from the Dynamic Neutron Albedo (DAN) instrument measurements made onboard the Curiosity rover during its active and passive operations of measuring the neutron flux albedo of the Mars surface. The instrument measurement profiles include estimates of water and chlorine content derived from data collected during several years of continuous operation. The DAN data was presented as pixels that had a regular size along the path of rover movement, which allowed for the analysis of the features of the crater geomorphology. A pixel size of 3×3 m was used to cover each individual measurement taken by the instrument, both active and passive methods. The values of water and chlorine content for each point along the rover's trajectory were provided, and values that correlated within a single pixel were averaged and assigned to that pixel.

Several space experiments are planned for probing the soil composition of the Moon and Mars onboard Luna 25, Luna 27, and ExoMars 2020 landers using instruments of the ADRON series. The method of active neutron and gamma ray logging, the main goals and objectives of these experiments, the content of the equipment, and the design and electronics of these instruments are described.

The laboratory experiment was conducted at Joint Institute for Nuclear Research with a prototype of planetary gamma-ray spectrometer (GRS) based on a High Purity Germanium (HPGe) detector and a proton detector (PD) configured with the GRS in the coincidence mode. The instrument set-up allows to detect gamma rays produced in the target irradiated by protons using integrated gamma-ray spectra (all detected gamma rays) as well as tagged gamma-ray spectra that select only photons synchronized with the proton detection. The latter option improves signal-to-noise ratio by selecting prompt photons produced in the irradiated target. The main objective was to conduct experiment with an irradiation of 11 samples of Rare Earth Elements (REEs) with high energy protons (170 MeV) to find a set of uniquely characterized gamma-ray lines that confidently indicate the presence of the given REE. These measurements are acquired to understand the conditions of a hypothetical space experiment on the lunar surface aimed for the reconnaissance of lunar resources. In this experiment, ambient gamma radiation is produced by charged particles of Galactic Cosmic Rays (GCRs).45 significant gamma-ray lines were found for 11 tested samples of REEs in total. This list includes 7 gammaray lines which have already been identified in the existing catalog of characteristic gamma-ray lines produced in the inelastic scattering reactions. 18 gamma-ray lines are unique and they were detected for an individual REE only. Other 27 detected gamma-ray lines are associated with several REEs and therefore were combined into 10 joint groups. Some groups are rather large and consists of 4 REEs. The proposed method of spectrometry with the options of time-integrated and tagged spectra allowed to determine the fraction of the gamma-ray lines, which occurs promptly at moment of proton-nuclei interaction. For some gamma-ray lines such a fraction is rather large and approaching 50%, and for some other gamma-ray lines it could be as small as 10-15%. The obtained experimental results were used to predict the expected intensities of the REEs gamma-ray lines in a future gamma-ray spectrometric experiment on the lunar surface. In particular, for a hypothetical lunar ore field it is estimated that a gamma-ray spectrometer with 10 times larger total effective area, than one used for the experimental set-up, may detect Cerium gamma-ray line at 553 keV after 1.6 h of signal accumulations.

Appreciable amounts of hydrogen-bearing compounds have been detected within the lunar polar regions. Estimating the effect of the presence of water ice on surface topographic roughness is important for future exploration and activities in the vicinity of the lunar pole. To investigate this issue, we analyzed the correlations between water equivalent hydrogen in the top 1-m surface layer and topographic roughness of lunar south polar regions. The results show that water ice probably plays an important role in the surface roughness at the hectometer scale, and might has a suppressive effect on surface roughness. In the detailed analysis, most the surface roughness at the floor of Shoemaker, Faustini, Slater and Sverdrup shows a decreasing trend with increasing water equivalent hydrogen at different decreasing slopes; Haworth shows slightly increasing trend, contrary to the trend of other studied craters. These observations may be related to small-scale topographic features at the surface and/or subtle changes in surface and subsurface WEH, which in turn affect the roughness characteristics in detail.

•Investigated are the radiation conditions in Mars orbit from May 2018 to June 2022.•Observed are 5 solar particle events (SPE) in Mars orbit in July 2021-March 2022.•The dose, dose equivalent and flux during SPE held15–19 February 2022 are biggest.•SPE recorded in Mars orbit are related to solar activity and coronal mass ejections.•Agreement of the flux time profiles measured by different detectors in Mars orbit.

An experiment on the proton beam of the JINR Phasotron with a laboratory prototype of a space-based gamma-ray spectrometer with tagged charged particles (GRS-TCP) with a semiconductor detector made of highly pure germanium and the results of the obtained measurements are considered. It is shown that the configuration of the space gamma-ray spectrometer with a semiconductor detector is the most effective for studying the composition of the near-surface soil of a celestial body from the board of a lander than with a scintillation one. The high spectral resolution of high-purity germanium makes it possible to detect nuclear lines with maximum sensitivity for a detector with a given mass, and the use of the “tagged charged particles” method makes it possible to practically eliminate the intrinsic background from the spacecraft and significantly increase the spatial resolution of the gamma spectrometer.