We jointly analyze data from the High-Energy Neutron Detector (HEND) onboard the NASA Mars Odyssey spacecraft and data from the Mars Orbiter Laser Altimeter (MOLA) onboard the Mars Global Surveyor ...spacecraft. The former instrument measures the content of hydrogen (in the form of H
2
O or OH) in the subsurface layer of soil and the latter instrument measures the surface albedo with respect to the flux of solar energy. We have checked the presence of a correlation between these two data sets in various Martian latitude bands. A significant correlation has been found between these data at latitudes poleward of 40° in the northern hemisphere and at latitudes 40°–60° in the southern hemisphere. This correlation is interpreted as evidence for the presence of stable water ice in these regions under a dry layer of soil whose thickness is determined by the condition for equilibrium between the condensation of water from the atmosphere and its sublimation when heated by solar radiation. For these regions, we have derived an empirical relation between the flux of absorbed solar radiation and the thickness of the top dry layer. It allows the burial depth of the water ice table to be predicted with a sub-kilometer resolution based on near-infrared albedo measurements. We have found no correlation in the southern hemisphere at latitudes >60°, although neutron data also suggest that water ice is present in this region under a layer of dry soil. We conclude that the thickness of the dry layer in this region does not correspond to the equilibrium condition between the water ice table and the atmosphere.
A concept is presented for a pressurized, water-cooled, pool-type research nuclear reactor IVV-3 under consideration as a replacement capacity for the operating IVV-2M reactor. The expanded ...experimental capabilities of the IVV-3 reactor, which are associated with an increase in the thermal power and neutron flux density in experimental bodies, will make it possible not only to keep the existing research and production base but also to become in-demand for solving new problems of the nuclear industry. The concept developed for the IVV-3 reactor is based on the principles of continuity of the layout solutions used for the IVV-2M reactor core and operational safety security of water moderated and cooled pool-type research reactors in our country and abroad.
The Dynamic Albedo of Neutrons (DAN) instrument on board Mars Science Laboratory has been operating successfully since the landing and has been making measurements regularly along Curiosity's ...traverse at the surface. DAN measures thermal (E < 0.4 eV) and epithermal neutrons (0.4 eV < E < ~1 keV) while operating in two different modes: active and passive. The active mode uses a pulsed neutron generator (PNG) to study the geological characteristics of the subsurface. In the passive mode, DAN measures the background neutron environment. This paper presents results of measurements in the passive mode from landing through to sol 100 and provides an interpretation of the data based on extensive Monte Carlo simulations. The main observations are summarized as follows: (1) the thermal neutron counts vary strongly along the rover traverse while the epithermal counts do not show much variation; (2) the neutrons from the Multi‐Mission Radioisotope Thermoelectric Generator (MMRTG) are a larger contributor to the DAN passive data than the Galactic Cosmic Ray (GCR)‐induced neutrons; (3) for the MMRTG neutrons, both the thermal and the epithermal counts increase as a function of the subsurface water content; (4) on the other hand, for the GCR‐induced neutrons, the thermal counts increase but the epithermal counts decrease as a function of the subsurface water content; and (5) relative contributions by the MMRTG and GCR to the DAN thermal neutron counts at the Rocknest site, where the rover was stationed from sol 59 to sol 100, are estimated to be ~60% and ~40%, respectively.
Key Points
The DAN passive mode measures the MMRTG neutrons and GCR‐induced neutrons
The thermal neutron counts show strong variability along the rover traverse
The majority of the DAN passive counts are from the MMRTG neutrons
The contemporary methods for improving the quality of welding of gas pipelines are considered, and new methods for decreasing magnetic blowout are proposed.
The IBR-2 (JINR) pulsed reactor is used in the field of solid state physics for experiments on extracted beams. It is predicted that the IBR-2 reactor will reach resource limits in 2032–2037. To keep ...and develop beam research at JINR, the development of a new pulsed neutron source has begun. According to estimates, the reactor will have average thermal power 12–15 MW, extracted by sodium coolant. At this power, the average flux density of thermal neutrons on the surface of the water moderator will reach 10
14
sec
–1
·cm
–2
and the peak density 5·10
16
sec
–1
·cm
–2
, which is more than 10 times higher than the analogous parameters of the operating IBR-2 reactor. The new reactor is supposed to use neptunium-based fuel. The main characteristics and concept of the new reactor are presented.
To elucidate the nature of permafrost in the shallow subsurface of Mars, we analyze jointly neutron albedo from the High Energy Neutron Detector (HEND) on the Mars Odyssey spacecraft and near‐IR ...(1064‐nm) surface reflectance from the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor. The first dataset measures the content of hydrogen (in the form of water or hydroxyl) in the soil, and the second yields the flux of absorbed solar energy by the surface. We identify a statistically–significant negative cross‐correlation between these data at latitudes poleward of 40° latitude in the northern hemisphere and in the latitude band 40°–60° in the southern hemisphere, which we interpret as evidence for the presence of stable water ice under a dry equilibrium top layer (ETL). We deduce an empirical relation between near‐IR reflectance and thickness of this ETL, which allows the burial depth of the water ice table to be estimated with km‐scale spatial resolution. We observe no correlation between neutron and near‐IR albedo within the southern hemisphere poleward of 60° latitude. While it is known from previously analyzed neutron and gamma‐ray data that subsurface water ice is present within this region and is covered by a layer of dry regolith, the absence of a correlation indicates that the thickness of this layer is not controlled by an equilibrium condition between the ice table and atmosphere.
We present a summary of the physical principles and design of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory (MSL) mission. The DAN instrument will use ...the method of neutron-neutron activation analysis in a space application to study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover.
The scientific objectives of neutron mapping of the Moon are presented as 3 investigation tasks of NASA's Lunar Reconnaissance Orbiter mission. Two tasks focus on mapping hydrogen content over the ...entire Moon and on testing the presence of water-ice deposits at the bottom of permanently shadowed craters at the lunar poles. The third task corresponds to the determination of neutron contribution to the total radiation dose at an altitude of 50 km above the Moon. We show that the Lunar Exploration Neutron Detector (LEND) will be capable of carrying out all 3 investigations. The design concept of LEND is presented together with results of numerical simulations of the instrument's sensitivity for hydrogen detection. The sensitivity of LEND is shown to be characterized by a hydrogen detection limit of about 100 ppm for a polar reference area with a radius of 5 km. If the presence of ice deposits in polar "cold traps" is confirmed, a unique record of many millions of years of lunar history would be obtained, by which the history of lunar impacts could be discerned from the layers of water ice and dust. Future applications of a LEND-type instrument for Mars orbital observations are also discussed.
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