D. I. Lisov’s research while affiliated with Russian Academy of Sciences and other places

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.

This paper presents the results of laboratory studies on the use of a new technology of selective laser melting to obtain experimental products from the lunar regolith without special additives. The main properties of the natural regolith, which significantly affect the fusion process, are determined. The first samples of a given geometry were obtained from labradorite and gabbro-diabase powders, which are natural analogues of lunar regolith, using this technology. The research results are planned to be used in the preparation of initial data for the development of the Lunar Printer space device as part of the complex of scientific equipment of the promising lunar project Luna-Grunt.

Plain Language Summary The Curiosity rover has been exploring layered sediments enriched with hydrated mineral phases which were formed in past epochs due to the interaction with fluids in Gale crater, Mars. Curiosity carries 10 science instruments to conduct remote and contact measurements and has already made ∼30 drill holes along its 30 km drive, testing samples of Martian soils and rocks. One of Curiosity's science tasks is to measure the elemental composition of the Martian surface and chlorine is considered here as an important chemical component that could tell us what has occurred on Mars in the past. Several instruments aboard Curiosity are capable of estimating the concentration of chlorine and we selected two of them (Dynamic Albedo of Neutrons and Alpha Particle X‐ray Spectrometer) to evaluate how chlorine is distributed with depth using data acquired at drill locations. We found that the chlorine distribution at Gale crater consists of two components: surficial chlorine with concentration >1%, possibly controlled by wind‐driven deposition of Cl‐rich dust and surface alteration, and subsurface chlorine with concentration <1%, likely a result of groundwater activity in the past.

Plain Language Summary The Dynamic Albedo of Neutrons (DAN) is a neutron spectrometer that searches for signs of water by measuring the content of neutron absorbing elements in the ground below the NASA's Curiosity rover. Data derived from DAN are presented in discrete pixels along the traverse of the rover. Each pixel contains estimations of water equivalent hydrogen (WEH) and absorption equivalent chlorine (AEC) content from neutron sensing. DAN observations were combined into the two types of 3 × 3 m pixels: Pixel with Active Data includes WEH and AEC content and Pixel of Passive Data includes WEH content. Each pixel has been assigned to the associated geological member of the Mars Science Laboratory stratigraphic column. Full DAN data volume for 27 km of the traverse were formatted as a table with more than 10,000 pixels. The large fraction of stratigraphic members (Bradbury, Pahrump Hills and others) have the mean WEH values between 2 and 3 wt.%, while other members of the second part of the traverse (Jura, Knockfarrill Hill, Glasgow, Pontours) have the mean values of WEH above 3 wt.%. Mean AEC value has no large variations for all tested stratigraphic members; it is equal to around 1 wt.% for the majority of the pixels.

Latitude (center of pixel) Associated Member of the Stratigraphic Column WEH values (wt.%) AEC values (wt.%)

Possible correlation is studied between Water Equivalent Hydrogen (WEH) in the Martian subsurface, as measured by the DAN (Dynamic Albedo of Neutrons) instrument along the Curiosity traverse, and the presence of hydrated minerals on the surface, as seen from the orbit by CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument onboard MRO (Mars Reconnaissance Orbiter). Cross-analysis of the subsurface WEH values from DAN passive measurements with the distribution of hydrated minerals over the surface of Gale crater according to Specialized Browse Product Mosaics is performed for the initial 20 km part of traverse. As a result, we found an increase up to 0.4 wt% of the mean WEH value for the surface areas with the spectral signatures of polyhydrated sulfates. The increase is shown to be higher with the more prominent spectral signature on the surface. Similar WEH increase for the two other types of hydrated minerals, such as monohydrated sulfates and phyllosilicates, was not found for the tested part of the traverse. Polyhydrated sulfates being a part of the sedimentary deposits composing the surface of Gale crater should have considerable thickness that is necessary for the subsurface neutron sensing by DAN measurements.

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 CeBr3 crystal for detection of gamma-ray along with its benefits for the detection of ⁴⁰K 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.