Hydrogen has been inferred to occur in enhanced concentrations within permanently shadowed regions and, hence, the coldest areas of the lunar poles. The Lunar Crater Observation and Sensing Satellite ...(LCROSS) mission was designed to detect hydrogen-bearing volatiles directly. Neutron flux measurements of the Moon's south polar region from the Lunar Exploration Neutron Detector (LEND) on the Lunar Reconnaissance Orbiter (LRO) spacecraft were used to select the optimal impact site for LCROSS. LEND data show several regions where the epithermal neutron flux from the surface is suppressed, which is indicative of enhanced hydrogen content. These regions are not spatially coincident with permanently shadowed regions of the Moon. The LCROSS impact site inside the Cabeus crater demonstrates the highest hydrogen concentration in the lunar south polar region, corresponding to an estimated content of 0.5 to 4.0% water ice by weight, depending on the thickness of any overlying dry regolith layer. The distribution of hydrogen across the region is consistent with buried water ice from cometary impacts, hydrogen implantation from the solar wind, and/or other as yet unknown sources.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
An updated set of goals and objectives for the Mercury Gamma and Neutron Spectrometer (MGNS) are presented based on the most recent findings of the MESSENGER mission. The updated design of MGNS with ...the new CeBr
3
crystal for detection of gamma-ray along with its benefits for the detection of
40
K and K/Th ratio are discussed. MGNS will then be capable of measuring the elemental composition of shallow subsurface in order to empirically evaluate the fittest model on the origin of Mercury, as well as the presence of possible water ice deposits on the permanently shadowed polar craters on the planet. We present the results of the first measurements in space performed during the instrument commissioning phase and during the first Earth flyby which occurred in April 2020.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
ExoMars is a two-launch mission undertaken by Roscosmos and European Space Agency. Trace Gas Orbiter, a satellite part of the 2016 launch carries the Fine Resolution Neutron Detector instrument as ...part of its payload. The instrument aims at mapping hydrogen content in the upper meter of Martian soil with spatial resolution between 60 and 200 km diameter spot. This resolution is achieved by a collimation module that limits the field of view of the instruments detectors. A dosimetry module that surveys the radiation environment in cruise to Mars and on orbit around it is another part of the instrument.
This paper describes the mission and the instrument, its measurement principles and technical characteristics. We perform an initial assessment of our sensitivity and time required to achieve the mission goal. The Martian atmosphere is a parameter that needs to be considered in data analysis of a collimated neutron instrument. This factor is described in a section of this paper. Finally, the first data accumulated during cruise to Mars is presented.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Results are presented for the LEND instrument onboard LRO for the detection of local spots of suppression and excess of epithermal neutron emission at the lunar poles. Twelve local Neutron ...Suppression Regions (NSRs) and Neutron Excess Regions (NERs) are detected. It is shown using the data from the LOLA and Diviner instruments that six NSRs have the empirical property “less local irradiation and lower temperature – fewer local neutrons.” These NSRs may be identified with spots of water‐ice rich permafrost on the Moon. It is shown that detected NSRs are include in both permanently shadowed and illuminated areas, and they are not coincident with Permanently Shadowed Regions (PSRs) at the bottom of polar craters, as has been commonly expected before LEND presented neutron data with high spatial resolution.
Key Points
Neutron suppression regions and neutron excess regions discovered
Empirical law
Water‐ice rich permafrost spots may be identified with these regions on the Moon
The laboratory demonstration of the space experiment was conducted at Joint Institute for Nuclear Research with a new type of planetary gamma-ray spectrometer (GRS-TCP) suite including a gamma-ray ...detector and a charged particle detector combined in coincidence mode. The proposed GRS prototype can select gamma-ray photons with time tags of charged particles of Galactic cosmic rays (GCR) from a predefined solid angle on the sky. It allows to collect gamma-rays only from a local spot on the irradiated surface under the rover or lander and rejects gamma-ray detections from the surrounding area/spacecraft body significantly improving signal-to-noise ratio. The main objective of this laboratory demonstration was to study the capability of this method to distinguish between local spots with different elemental compositions that could be passed by the rover along its traverse. For this purpose, the soil sample simulants corresponding to the different types of Martian regolith identified by Curiosity rover were created and tested by laboratory measurements. It was experimentally shown that our method of spectroscopy of gamma-rays with tags of charged particles could reliably detect local variations of the planetary regolith.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A new concept is proposed for the study of the elemental composition of planetary surfaces on landed missions through the coincident detection of gamma rays induced by Galactic Cosmic Ray (GCR) ...charged particles and the detection of the incident charged particle that produces the gamma ray. Charged particle detection is used to tag all instances of GCR interaction in a selected volume of the subsurface that results in the emission of secondary gamma rays. Using the criteria of a tagged GCR particle and coincident gamma ray detection, one may measure gamma ray spectra produced in a selected subsurface volume by GCR induced spallation and inelastic scattering of fast neutrons. The proposed new technique minimizes the contribution of gamma radiation from other regions of the subsurface and spacecraft structural components that may add background to the measured gamma-ray spectrum from the selected soil volume.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The description of Dynamic Albedo of Neutrons (DAN) experiment is presented, as a part of the NASA’s Mars Science Laboratory mission onboard the mars rover Curiosity. The instrument DAN includes ...Pulsing Neutron Generator (PNG) producing pulses of 14.1 MeV neutrons for irradiation of subsurface material below the rover, and Detectors and Electronics (DE) unit, which operates the instrument itself and measures the die-away time profiles of epithermal and thermal neutrons following each neutron pulse. It is shown that the DAN investigation will measure a content of hydrogen along the path of the MSL rover, and it will also provide information about a depth distribution of hydrogen at 10–20 regions selected for the detailed studies and sampling analysis.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper presents the results of the analysis of data from the BTN-Neutron space experiment carried out onboard the Russian module Zvezda, which is part of the
International Space Station
. The ...long observation period from 2008 to 2019 covers the end of the 23rd and almost all of the 24th solar cycle. This made it possible to estimate the amplitude of long-period variations of the neutron background outside the
ISS
due to solar modulation of galactic cosmic rays. For equatorial regions with a high geomagnetic-cutoff index, it does not exceed 10%, while the neutron background changes by almost 1.5–2 times in high-latitude regions around the Earth’s magnetic poles and the South Atlantic Magnetic Anomaly. For the periods of minimum and maximum solar activity within the 24th solar cycle, according to the BTN-Neutron experiment, maps of the distribution of the neutron-component power were constructed and the average neutron-dose rates that the cosmonauts could receive during these periods were estimated. It was shown that, for maximum and minimum solar activity, the average neutron dose rate varies from 25 to 35 µSv/day for neutrons with energies below 15 MeV.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Data gathered with the Dynamic Albedo of Neutron (DAN) instrument onboard rover Curiosity were analyzed for variations in subsurface neutron flux and tested for possible correlation with local ...geological context. A special DAN observation campaign was executed, in which 18 adjacent DAN active measurements were acquired every 0.75–1.0 m to search for the variations of subsurface hydrogen content along a 15 m traverse across geologic contacts between the Sheepbed and Gillespie Lake members of the Yellowknife Bay formation. It was found that several subunits in Sheepbed and Gillespie Lake could be characterized with different depth distributions of water‐equivalent hydrogen (WEH) and different chlorine‐equivalent abundance responsible for the distribution of neutron absorption elements. The variations of the average WEH at the top 60 cm of the subsurface are estimated at up to 2–3%. Chlorine‐equivalent neutron absorption abundances ranged within 0.8–1.5%. The largest difference in WEH and chlorine‐equivalent neutron absorption distribution is found between Sheepbed and Gillespie Lake.
Key Points
DAN special campaign in Yellowknife Bay
DAN local measurements of water and chlorine abundance
Correlation of DAN measurements and geological context
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•LEND/LRO instrument neutron counting data sets have been analyzed to create high resolution maps of epithermal neutron flux at polar regions of the Moon.•The conversion from epithermal neutron flux ...to the H/H2O abundances is presented based on the simple subsurface models.•The polar lunar maps (poleward 70S/70N) of homogeneous hydrogen distribution are derived and discussed.
We present a method of conversion of the lunar neutron counting rate measured by the Lunar Reconnaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) instrument collimated neutron detectors, to water equivalent hydrogen (WEH) in the top ∼1m layer of lunar regolith. Polar maps of the Moon's inferred hydrogen abundance are presented and discussed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF
