Over 60 years of spacecraft exploration has revealed that the Earth's Moon is characterized by a lunar crust
dominated by the mineral plagioclase, overlying a more mafic (richer in iron and ...magnesium) mantle of uncertain composition. Both crust and mantle formed during the earliest stages of lunar evolution when late-stage accretional energy caused a molten rock (magma) ocean, flotation of the light plagioclase, sinking of the denser iron-rich minerals, such as olivine and pyroxene, and eventually solidification
. Very large impact craters can potentially penetrate through the crust and sample the lunar mantle. The largest of these craters is the approximately 2,500-kilometre-diameter South Pole-Aitken (SPA) basin
on the lunar far side. Evidence obtained from orbiting spacecraft shows that the floor of the SPA basin is rich in mafic minerals
, but their mantle origin is controversial and their in situ geologic settings are poorly known. China's Chang'E-4 lunar far-side lander recently touched down in the Von Kármán crater
to explore the floor of the huge SPA basin and deployed its rover, Yutu-2. Here we report on the initial spectral observations of the Visible and Near Infrared Spectrometer (VNIS)
onboard Yutu-2, which we interpret to represent the presence of low-calcium (ortho)pyroxene and olivine, materials that may originate from the lunar mantle. Geological context
suggests that these materials were excavated from below the SPA floor by the nearby 72-km-diameter Finsen impact crater event, and transported to the landing site. Continued exploration by Yutu-2 will target these materials on the floor of the Von Kármán crater to understand their geologic context, origin and abundance, and to assess the possibility of sample-return scenarios.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Dust deposition is one of the most predominant processes occurring on Mars. Until now, just a few in situ observations have been conducted to investigate the Martian dust. The Multispectral Camera ...(MSCam) onboard the Zhurong rover with its calibration target can be used to monitor dust deposition, providing a new ground observation. In this work, we focused on the observations of the MSCam calibration target to retrieve atmospheric optical depth and dust deposition rate over the first 300 sols. The derived atmospheric optical depths are around 0.44, suggesting relatively low airborne dust. The estimated dust deposition rate reveals a distinctive deposition process compared with that of other rovers or landers. Notably, no evident dust is presented during the initial 110 sols, after which dust starts to accumulate. Combining in situ meteorological measurements and numerical modeling, wind speed could be a critical factor to control the dust deposition rate.
Plain Language Summary
The Multispectral Camera (MSCam) onboard the Zhurong rover with its calibration target can be used to estimate the abundance of airborne dust and monitor the dust deposition from the atmosphere to the surface. With the first 300 sols of MSCam observations, we analyzed the temporal variations of the suspended dust and deposited dust on the calibration target. The results demonstrate that the atmosphere of Zhurong landing site has a relatively low dust content over the first 300 sols. The dust deposition rate shows a different deposition pattern from other rovers or landers. Benefiting from the in situ measured wind speed and the numerical modeling, we found that wind speed may play an important role in controlling the dust deposition rate.
Key Points
The Zhurong rover documented the atmospheric and deposited dust variations over the first 300 sols of traverse
The estimated dust deposition rate is relatively low and shows a distinctive pattern compared with other rovers
Wind speed plays a significant role in controlling the dust deposition
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The Tianwen-1 mission is China’s first Mars exploration mission. To complete the scientific objectives of “orbiting, landing, and patrolling” in one mission, thirteen instruments for acquiring ...multi-disciplinary data are configured. The data products with rich ancillary data and flexible structures will facilitate the data application. To integrate the requirements of experts from disparate disciplines and leverage new information technologies, a complete redesign of data products is promoted in the Tianwen-1 mission. We discuss the whole process of data product generation from the data pipeline design to data validation. We design the various data products according to the application requirements of each data type, including radar echo data, spectrum data, image data, energy spectrum data, magnetic field data, meteorological data, and acoustic data. Since various error sources will exist in the generation chain of the data products, data validation is essential before release to the public; the validation activities are discussed at the end. We deliver these scientific products to the community in a timely manner, with ancillary information and quality information. This paper can provide practical reference for Tianwen-1 data application.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Navigation and Terrain Cameras (NaTeCams) are binocular stereo cameras mounted on the Tianwen-1 Mars Rover. The NaTeCams are primarily designed to provide support for the guidance, navigation, ...and control of the rover, and they can also be used for scientific observations. NaTeCam is a color imaging system using a complementary metal oxide semiconductor (CMOS) active pixel sensor (APS). An overview of the camera design is provided. Preflight calibration and performance are also discussed. Specific details about the camera operation and ground test are presented.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Chang'E-4 (CE-4) was the first mission to accomplish the goal of a successful soft landing on the lunar farside. The landing trajectory and the location of the landing site can be effectively ...reconstructed and determined using series of images obtained during descent when there were no Earth-based radio tracking and the telemetry data. Here we reconstructed the powered descent trajectory of CE-4 using photogrammetrically processed images of the CE-4 landing camera, navigation camera, and terrain data of Chang'E-2. We confirmed that the precise location of the landing site is 177.5991°E, 45.4446°S with an elevation of -5935 m. The landing location was accurately identified with lunar imagery and terrain data with spatial resolutions of 7 m/p, 5 m/p, 1 m/p, 10 cm/p and 5 cm/p. These results will provide geodetic data for the study of lunar control points, high-precision lunar mapping, and subsequent lunar exploration, such as by the Yutu-2 rover.
Landing site selection is of fundamental importance for lunar landing mission and it is closely related to the scientific goals of the mission. According to the widely concerned lunar science goals ...and the landing site selection of the ongoing lunar missions; China has carried out the selection of landing site for a series of Chang’ E (CE) missions. Under this background, this paper firstly introduced the principles, process, method and result of landing site selection of China’s Lunar Exploration Program (CLEP), and then analyzed the support of the selected landing sites to the corresponding lunar research. This study also pointed out the outcomes that could possibly contribute to the key lunar questions on the basis of the selected landing sites of CE-4 and CE-5 such as deep material in South Pole-Aitken (SPA) basin, lunar chronology, volcanic thermodynamics and geological structure evolution history of the Moon. Finally, this approach analyzed the development trend of China’s follow-up lunar landing missions, and suggested that the South Pole Region of the Moon could be the landing site of high priority for the future CE missions.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Chang'E‐4, with the Yutu‐2 rover, is the first lunar probe to successfully land and conduct a tour on the far side of the Moon from early 2019. We analyze the physical and mechanical characteristics ...of lunar soil through the in situ terrain data collected by the panoramic camera onboard the Yutu‐2 rover. With the slip ratio and wheel sinkage obtained by the derived Digital Orthophoto Map (DOM) and Digital Elevation Model (DEM), the mechanical parameters of lunar soil are derived from the slip‐sinkage model. These mechanical parameters and wheel size of the rover are used to obtain the pressure‐sinkage curves, which can estimate the lunar soil strength. The experimental results indicate that the soil strength at the Chang'E‐4 landing site is much higher than that at the Chang'E‐3 landing site. The discrepancies in lunar soil strength between the two landing sites may be related to the local surface topography and degree of space weathering.
Plain Language Summary
The knowledge of the physical and mechanical characteristics of lunar soil is of fundamental importance because it is the basis for mineral resource exploration and engineering activity aimed at the construction of lunar bases. The Chang'E‐4 landing site is within the mare floor of the Von Kármán crater inside the South Pole‐Aitken (SPA) basin. The ejecta from the nearby impact craters has covered the Chang'E‐4 landing area. Besides, the lunar soil of the Chang'E‐4 landing area has been relatively mature. Here, a method of analyzing the characteristics of lunar soil is introduced to provide an opportunity to understand the physical and mechanical properties of the mature lunar soil at the Chang'E‐4 landing site. With the terrain data collected by the panoramic camera onboard the Yutu‐2 rover, we can get the relationship curve of the interaction between the rover wheels and lunar soil, such as the pressure‐sinkage curve. The pressure‐sinkage curves can intuitively reflect the discrepancies of lunar soil strength at the Chang'E‐4 and Chang'E‐3 landing sites, which may bear a big relationship to the local surface morphology and degree of space weathering.
Key Points
The slip ratio can be estimated by Digital Orthophoto Map and the wheel sinkage can be derived from Digital Elevation Model
The pressure‐sinkage curves can intuitively reflect the discrepancies of lunar soil strength at different landing sites
The lunar soil strength at the Chang'E‐4 landing site nearby is higher than that at the Chang'E‐3 landing site
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Non-uniformity in the response of spectral image elements is an inevitable phenomenon in hyperspectral imaging, which mainly manifests itself as the presence of band noise in the acquired ...hyperspectral data. This problem is prominent in the infrared band owing to the detector material, operating environment, and other factors. Non-uniformity is an important factor that can affect the quality of the hyperspectral data, which has a serious impact on both data analysis and applications and requires corrections via technical means wherever possible. This paper proposes a novel target-based non-uniformity self-correction method for infrared push-broom hyperspectral images. The Mars Mineralogical Spectrometer (MMS) onboard the Tianwen-1 orbiter was used as the research and application object. The model is constructed and applied to the target scene characteristics and detection patterns of Mars remote sensing exploration, which are combined with the causes of noise generation in the infrared spectral image bands. The design of the MMS dual-channel Visible-Near-Infrared (V-NIR) and Near-Mid-Infrared (N-MIR) co-field of view co-target detection and laboratory calibration data for the V-NIR spectral band can achieve non-uniformity corrections (NUCs). Therefore, for the MMS in-orbit Mars exploration mission, the method selected spectral data (920–1055 nm) characterized by a reduced atmospheric influence to iteratively obtain the homogeneous region, which was used to calculate the non-uniformity correction factor for the N-MIR spectral band. This method was compared, validated, and evaluated with other conventional methods using both laboratory and in-orbit hyperspectral data. The results showed that the experimental data corrections were comparable to laboratory calibrations, with a maximum relative deviation of <2.6%. These results prove that our method not only provides an excellent non-uniformity correction, but also ensures spectral fidelity. It can thus be used as a non-uniformity correction process for the MMS and similar hyperspectral imagers.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The Yutu‐2 rover of Chang'E‐4 encountered four special rocks along its path. The onboard Visible and Near‐infrared Imaging Spectrometer (VNIS) collected their spectral data at close range. In this ...work, we focus on the visible/near‐infrared image cubes captured by the VNIS. Simple classification was performed using the K‐means algorithm based on the 750/900 nm spectral ratios to highlight the surface material variations. In the case of narrow measurements of phase angle, the classification results were not significantly affected by viewing geometry. Varying degrees of dust coverage on the rock surfaces were revealed, which may be attributed to ejecta deposition and dust electrostatic levitation. The spectral shapes of the less dust‐covered surfaces indicated that these rocks are dominated by mafic materials, suggesting they may not originate from the lunar upper crust. The influence of dust coverage on spectral measurement of rocks was also confirmed, which significantly attenuates the absorption depths.
Plain Language Summary
The Chang'E‐4 (CE‐4) mission is the first probe to successfully land on the lunar farside. The rover of CE‐4 mission, Yutu‐2, has come across four curious rocks during its exploration. To reveal their compositions, Yutu‐2 rover conducted close investigations and captured their spectral images using the onboard Visible and Near‐infrared Imaging Spectrometer instrument (VNIS). We analyzed these data and found an interesting phenomenon that these rock surfaces are partly covered by lunar dust. Dust coverage obscures the information from the rocks themselves, making it difficult to decipher the rock compositions if not carefully handled. Fortunately, benefiting from the spatial insight provided by the VNIS, we analyzed the areas with less dust coverage on rock surfaces and determined that these rocks are likely dominated by mafic materials, suggesting that they may not originate from the lunar upper crust.
Key Points
The spectral variations of the rock surfaces are revealed using the visible/near‐infrared image cubes collected by the Chang'E‐4 (CE‐4) rover
The four rocks encountered by the CE‐4 rover may be all dominated by mafic materials but with different degrees of dust coverage
The absorption depths of the rock surface spectra in the field of view are significantly attenuated as a result of dust coverage
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
