Two Lunar Mare Soil Simulants

Two new lunar mare soil simulants,NAO-2 and NAO-3,have been created in National Astronomical Observatories(NAO),Chinese Academy of Sciences.These two simulants were produced from low-titanium basalt and high-titanium basalt respectively.The chemical composition,mineralogy, particle size distribution,density,angle of internal friction,and cohesion of both simulants have been analyzed,indicating that some characteristics of NAO-2 and NAO-3 are similar to those of Apollo 14 and Apollo 11 landing site soils.NAO-2 and NAO-3 will be of great benefit to the scientific and engineering research on lunar soil.

Mineral abundances and different levels of alteration around Mawrth Vallis,Mars

Spectral indices from OMEGA hyperspectral data show that there are two main phyllosilicates exposed in and around Mawrth Vallis:Al phyllosilicates and Fe/Mg phyllosilicates.Detailed analysis of CRISM spectra shows that Al phyllosilicates such as montmorillonite,hydrated silica,kaolinite;Fe/Mg phyllosilicates such as nontronite,saponite,serpentine are widespread on the light-toned outcrops.Though similar stratigraphical sequences,morphologies and textures are observed on both sides of Mawrth Vallis from HiRISE images,suggesting that the geological processes that formed these units must have operated at a regional scale;the multiple endmember spectral mixture analysis(MESMA) derived mineral abundance indicates that there is a higher level of alteration in the western side relative to the eastern side.We suggest that the observed phyllosilicates,stratigraphical sequences and different levels of alteration might have been caused by sedimentary deposition processes in which the composition of the external source sediment or the local solution was different,or by a pedogenic process closely related to the leaching of abundant liquid water with different chemical properties.

Return to the Moon:New perspectives on lunar exploration

Lunar exploration is deemed crucial for uncovering the origins of the Earth-Moon system and is the first step for advancing humanity’s exploration of deep space.Over the past decade,the Chinese Lunar Exploration Program(CLEP),also known as the Chang’e(CE)Project,has achieved remarkable milestones.It has successfully developed and demonstrated the engineering capability required to reach and return from the lunar surface.Notably,the CE Project has made historic firsts with the landing and on-site exploration of the far side of the Moon,along with the collection of the youngest volcanic samples from the Procellarum KREEP Terrane.These achievements have significantly enhanced our understanding of lunar evolution.Building on this success,China has proposed an ambitious crewed lunar exploration strategy,aiming to return to the Moon for scientific exploration and utilization.This plan encompasses two primary phases:the first crewed lunar landing and exploration,followed by a thousand-kilometer scale scientific expedition to construct a geological cross-section across the lunar surface.Recognizing the limitations of current lunar exploration efforts and China’s engineering and technical capabilities,this paper explores the benefits of crewed lunar exploration while leveraging synergies with robotic exploration.The study refines fundamental lunar scientific questions that could lead to significant breakthroughs,considering the respective engineering and technological requirements.This research lays a crucial foundation for defining the objectives of future lunar exploration,emphasizing the importance of crewed missions and offering insights into potential advancements in lunar science.

Geological context of the Chang’e-6 landing area and implications for sample analysis

Research on returned samples can provide ground truth for the study of the geological evolution history of the Moon.However,previous missions all collected samples from the near side of the Moon,which is significantly different from the far side of the Moon in terms of the thickness of the lunar crust,magma activity,and composition.Therefore,the samples from the far side of the Moon are of great significance for a comprehensive understanding of the history of the Moon.China’s Chang’e-6(CE-6)probe has successfully landed on the lunar far side and will return samples in the coming days.With the precise location of the CE-6 landing site,a detailed analysis of the geological background is conducted in this research.The landing site of CE-6 is within the Apollo crater,which is inside the largest impact basin on the Moon,i.e.,the South Pole-Aitken(SPA)basin.According to the numerical simulation of the formation process of the SPA basin,CE-6 landed at the edge of the SPA impact melting zone,which is presumably composed of impact melt of the lunar mantle.The Apollo crater subsequently excavated deep material again,which constitutes the basement of the CE-6 landing area.Later,erupted basalt covered these basement rocks,and they also constitute the main source of the CE-6 samples.Based on the dating method of crater size-frequency distribution,we find that the basalt is2.50 Ga.The CE-6 samples also possibly contain basement rocks as excavated and ejected by craters,and they can provide crucial information for our understanding of lunar geological history along with the basalt samples.

Scientists eager for Chang’e-6 lunar farside samples to bring new discoveries

The tidal locking effect keeps the Moon consistently presents its one side—the near side—to Earth,rendering the other side—the far side—inaccessible for people standing on Earth.Consequently,the far side of the Moon remained shrouded in mystery for human observers until the onset of space exploration.In 1959,the Soviet Union’s Luna 3 spacecraft returned the first views ever of the far side of the Moon.Despite the blurriness of the photo by contemporary standards,the stark contrast between the near side and far side of the Moon was striking.Since then,a growing number of orbital probes have revealed significant differences between the two sides of the Moon,including lunar crust thickness,magma activities,and compositions.However,the origins of these differences remain unexplained.

Geospatial technologies for Chang’e-3 and Chang’e-4 lunar rover missions

This paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions.Photogrammetric mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing,and to produce centimeter-resolution topographic products in near real-time after landing.Visual positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after landing.During surface operations,visual-positioning-based rover localization was performed routinely at each waypoint using Navcam images.The topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning,science target selection and scientific investigations.A GIS-based digital cartography system was also developed to support rover teleoperation.

Progresses and prospects of impact crater studies

Crater is a geologic structure in solid bodies(including the terrestrial planets, moons, and asteroids) formed by hyperspeed impact, and the impact process is extremely important to the formation and evolution of these celestial bodies. This paper presents a review of the studies on remote sensing observation, formation mechanism, and scientific application of craters. On the remote sensing study of craters, the topographic characteristics of the micro-craters, simple craters, complex craters, and impact basins are described,the related parameters in the morphological studies of craters are subsequently introduced, and the distribution characteristics of the minerals and rock types during the impact excavation process are analyzed,the methods of crater identification and the crater databases on the Moon, Mars, Ceres, and Vesta are summarized. On the studies of crater formation mechanism, the general formation process of the craters is firstly described, and then the most frequently used methods are presented, and the importance of the empirical equations is also elucidated. On the scientific applications of the craters, the principle and currently utilization of the planetary surface dating method with crater size-frequency distribution are firstly presented, and the applications, including modeling the lunar regolith formation and thickness derivation of both the regolith and basalt, are reviewed. Finally, the future prospects of the formation mechanism study of the craters are discussed.

Hydrocode Simulation of the Impact Melt Layer Distribution underneath Xiuyan Crater, China

In this research, we studied the distribution of impact melt layers underneath Xiuyan crater using hydrocode simulation. The target was modeled by granite based on the rock type distribution around the crater and projector by iron, because most small and isolated terrestrial craters are formed by iron projectile. The simulated crater diameter and depth are 1 710 and 320 m, respectively, which are in good agreement with observations of 1 800 and 307 m（except for the postimpact lacustrine sedimentation）. The validated model shows that impact melt materials were first formed along the transient crater floor and wall by highshock pressure, and then refilled inward the crater along with collapse of the crater wall. The final style of impact melt materials is interbedded with shock breccia underneath the crater center, which is verified through two layers in the borehole located in the crater center.

Lunar Evolution Analysis Based on Numerical Simulations of Typical Lunar Impact Craters

Impact craters are one of the most important landforms on the lunar surface,playing a crucial role in the formation and later evolution of the Moon.For example,as a primary source of remote sensing observations and lunar samples,lunar regolith is predominantly composed of impact ejecta.Based on their morphologies,lunar impact craters with increasing sizes can be classified into simple craters,complex craters,and multiring basins,and they play different roles in lunar evolution.In our study,we conducted numerical simulations of the South Pole-Aitken basin and the Orientale basin on the lunar surface,as well as the Aristarchus complex crater and the Zhinyu simple crater.The resultant effects of them are further analyzed.Because Zhinyu crater is relatively close to the Chang’e-4 landing site,while Aristarchus crater is relatively close to the Chang’e-5 landing site,their simulation results have direct significance for interpreting the corresponding exploration data from both missions.The numerical simulation results demonstrate that the formation of large basins not only affects the subsurface structure within the basin but also significantly disturbs the surrounding geological layers.Complex and simple craters mainly disturb the subsurface layers within the crater,but complex craters can cause uplift of the underlying strata.These impact processes dominate the primary geological framework of the lunar surface,depositing ejecta materials of varying thicknesses from different depths,which has important implications for future sample collection missions.In conclusion,impact processes are one of the primary driving forces in the lunar evolution.

Development of the ignition delay prediction model of n-butane/hydrogen mixtures based on artificial neural network

Based on the experimental ignition delay results of n-butane/hydrogen mixtures in a rapid compression machine,a Genetic Algorithm(GA)optimized Back Propagation(BP)neural network model is originally developed for ignition delay prediction.In the BP model,the activation function,learning rate and the neurons number in the hidden layer are optimized,respectively.The prediction ability of the BP model is validated in wide operating ranges,i.e.,compression pressures from 20 to 25 bar,compression temperatures from 722 to 987 K,equivalence ratios from 0.5 to 1.5 and molar ratios of hydrogen(X_(H2))from 0 to 75%.Compared with the BP model,the GA optimized BP model could increase the average correlation coefficient from 0.9745 to 0.9890,in the opposite,the average Mean Square Error(MSE)decreased from 2.21 to 1.06.On the other hand,to assess the BP-GA model prediction ability in the never-seen-before cases,a limited BP-GA model is fostered in the𝑋X_(H2) range from 0 to 50%to predict the ignition delays at the cases of𝑋X_(H2)=75%.It is found that the predicted ignition delays are underestimated due to the training dataset lacking of“acceleration feature”that happened at𝑋X_(H2)=75%.However,three possible options are reported to improve the prediction accuracy in such never-seen-before cases.