Mare Imbrium Research Articles

Late stage Imbrium volcanism on the Moon: Evidence for two source regions and implications for the thermal history of Mare Imbrium

Abstract Large open fissures or volcanic rifts can form in volcanic terrain and they are also conduits for magma ascending through the lunar crust. On the Moon, we investigated two volcanic source regions within Mare Imbrium by tracking surface morphologic features and compositional information. The Euler source region is situated at the southwest edge of the basin, while the Lambert source region lies off the south margin of the Imbrium mascon. Survey of dike surface manifestations in Euler source site suggest that dikes are the possible source of the local upper basaltic flows and the last lava phases with well developed scarps near the Euler crater, which extend northeast to the basin center. The Euler dike swarm are radial to the basin and reveal possible dike-to-conduit transition mechanism. They reveal radial subsurface fractures which may be tensional cracks preceding to the emplacement of the last stage of the mare fill. Of these, the largest dike has a more than 100 km length. The spatial arrangement of tectonic and volcanic features in Lambert source site is directly or indirectly controlled by the regional compression and extension stresses associated with flexure in response to mascon and basalt loading. In addition, compositional variation trends show a general southwest-to-northeast flooding direction of the exposed high-Ti basalts. This will have important implications for both the Imbrium basin's mare volcanism and for the thermal evolution of Mare Imbrium and the Moon.

Comparison of physical and chemical properties of the surface in the regions of operation of the Lunokhod-1 and Yutu rovers on the Moon

Through the example of comparison of the natural features of two regions in the northern part of Mare Imbrium, that were directly investigated in detail with remotely controlled rovers on the lunar surface, the capabilities of combining orbital remote measurements of the physical and mechanical properties and the chemical composition of the lunar soil with their direct measurements have been shown. From the remotely determined spectropolarimetric and gamma-spectrometric characteristics of the regolith surface layer, the exposure age (the maturity), the mean effective size of particles of the fine fraction, the absolute age of the formations, and the iron content in the soil were estimated. To compare the characteristics of the considered regions, the results of the investigations carried out directly on the lunar surface by the Lunokhod-1 rover and the analogous vehicle Yutu were used.

An object-based classification method for automatic detection of lunar impact craters from topographic data

Identification of impact craters is a primary requirement to study past geological processes such as impact history. They are also used as proxies for measuring relative ages of various planetary or satellite bodies and help to understand the evolution of planetary surfaces. In this paper, we present a new method using object-based image analysis (OBIA) technique to detect impact craters of wide range of sizes from topographic data. Multiresolution image segmentation of digital terrain models (DTMs) available from the NASA’s LRO mission was carried out to create objects. Subsequently, objects were classified into impact craters using shape and morphometric criteria resulting in 95% detection accuracy. The methodology developed in a training area in parts of Mare Imbrium in the form of a knowledge-based ruleset when applied in another area, detected impact craters with 90% accuracy. The minimum and maximum sizes (diameters) of impact craters detected in parts of Mare Imbrium by our method are 29m and 1.5km, respectively. Diameters of automatically detected impact craters show good correlation (R2>0.85) with the diameters of manually detected impact craters.

The scale of late-stage basalts in Mare Imbrium

The basaltic volcanism is one of the most important geologic processes of the Moon, which reveals its interior evolution. As lunar basalts are formed from the partial melting of mantle materials, the volume of basalts reflects the size and the degree of partial melting of the source region. The Eratosthenian volcanism deposited large scale of high/medium-Ti basalts in Mare Imbrium, which could provide key information for studying the late-stage lunar volcanism in Mare Imbrium. Using a variety of remote sensing data and techniques (topographic profile and crater excavation method), we studied the scale of the Upper and Lower Eratosthenian (UEm and LEm) basalts in Mare Imbrium. The results show that the UEm is 13–33 m thick with several layers of individual lava (7–15 m) inside, and the thickness of LEm is 14.49–43.61 m. Adding the volume of exposed UEm basalts (~539.3 km3), the volume of exposed LEm basalts (~5198 km3) and the volume of young basalts underlying UEm (~55 6.2 km3) together, the total volume of the late-stage basalts in Mare Imbrium is ~6479 km3. It’s far lower than that of the Schaber’s estimation (~4×104 km3). The volume of the exposed UEm basalts accounts for only about 1/8 of the volume of the exposed LEm basalts, which means that basaltic eruption decreases with time during the Eratosthenian Period in Mare Imbrium. Besides, we estimated the decrease of the areal flux of Em5–Em7: Em5 (249.56 km2/Ma), Em6 (39.49 km2/Ma) and Em7 (46.89 km2/Ma). These results indicate that the basaltic volcanism receded with time during the Eratosthenian Period.

Geological investigations of Luna 17, Apollo 15 and Chang’E-3 landing sites at Mare Imbrium of the Moon

The Imbrium basin is one of the most prominent geologic units on the lunar nearside, and also significant exploration target for soft-landing missions. Till now, three lunar missions, USSR’s Luna 17, American Apollo 15 and Chinese Chang’E-3, have successfully soft-landed and conducted surface investigation at this basin. Employing the surface images and other data acquired by the three missions, we analyze the geologic characteristics of the three landing sites, mainly focusing on the regional geologic context, impact craters, surface boulders and regolith materials. We find that, the Lunar 17 and Chang’E-3 spacecraft landed on the relatively younger Eratosthenian mare basalt units, respectively, where massive basaltic bedrocks are exposed at the wall and rim of some small craters, and some of these exposed boulders present columnar jointing, while the Apollo 15 landed on the relatively older Imbrian lava plains, where surface boulders are seldom present. There exposed some layered basalts at the wall of the Hadley Rille, and columnar jointing structure is also observed at some boulders exposed at the rille floor and rim. We observe some possible lineaments on the surface images. We propose that these possible lineaments are caused by slightly undulant lunar surface illuminated under relatively low sun elevation angles, which is supported by our simulation experiments. The comparison of the three landing sites indicates that impacting history, volcanic activities, space weathering and other important geologic processes are regionally and locally inhomogeneous on the Moon, future lunar surface in-situ and sample-return missions will strengthen our understanding of the geologic evolutionary history of the Moon.

Photometric characterization of the Chang’e-3 landing site using LROC NAC images

China’s robotic Chang’e-3 spacecraft, carrying the Yutu rover, touched down in Mare Imbrium on the lunar surface on 14 December 2013. The Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) imaged the site both before and after landing. Multi-temporal NAC images taken before and after the landing, phase-ratio images made from NAC images taken after the landing, and Hapke photometric techniques were used to evaluate surface changes caused by the disturbance of regolith at the landing site (blast zone) by the descent engines of the Chang’e-3 spacecraft. The reflectance of the landing site increased by 10±1% (from I/F=0.040 to 0.044 at 30° phase angle) as a result of the landing, a value similar to reflectance increases estimated for the Apollo, Luna, and Surveyor landing sites. The spatial extent of the disturbed area at the Chang’e-3 landing site, 2530m2, also falls close to what is predicted on the basis of correlations between lander mass, thrust, and blast zone areas for the historic landed missions. A multi-temporal ratio image of the Chang’e-3 landing site reveals a main blast zone (slightly elongate in the N–S direction; ∼75m across N–S and ∼43m across in the E–W direction) and an extended diffuse, irregular halo that is less reflective than the main blast zone (extending ∼40–50m in the N–S direction and ∼10–15m in the E–W direction beyond the main blast zone). The N–S elongation of the blast zone likely resulted from maneuvering during hazard avoidance just prior to landing. The phase-ratio image reveals that the blast zone is less backscattering than surrounding undisturbed areas. The similarities in magnitude of increased reflectance between the Chang’e-3 landing site and the Surveyor, Apollo, and Luna landing sites suggest that lunar soil reflectance changes caused by interaction with rocket exhaust are not significantly altered over a period of 40–50years. The reflectance changes are independent of regolith composition, indicating that they are caused by a change in the physical properties of the regolith, likely microscopic to macroscopic smoothing of the surface, and possibly a change in surface maturity by removal of highly mature very fine-grained regolith components.

Petrology and provenance of a very‐low‐titanium picrite clast in lunar highland regolith breccia 15295

Clast 100 in regolith breccia 15295 could be a key to resolving the relationship(s) between mare basalts and lunar picritic glasses. The clast is basaltic, with texture, mineralogy, mineral compositions, and calculated bulk composition suggesting that it crystallized in a thick lava flow or shallow intrusive body from a very-low-titanium (VLT) basaltic magma. The estimated bulk composition of clast 15295,100 is primitive (i.e., magnesian) compared to those of known VLT basalts, and is very close to those of VLT picritic green glasses, especially the Apollo 14 A green glass. From these similarities, we infer that clast 15295,100 is a crystalline product of a picritic magma similar to the Apollo 14 A glass. Clementine and M3 remotely sensed data of the lunar surface were used to find areas that have chemical compositions consistent with those of clast 15295,100, not only near the Apollo 15 site, but in a broad region surrounding the site. Two regions are consistent with clast's 15295,100 compositional data. The larger region is in southern Mare Imbrium, and a smaller region is in the eastern half of Sinus Aestuum. These locations should be considered as candidates for future missions focusing on sample science.

Structural analysis of lunar subsurface with Chang׳E-3 lunar penetrating radar

Geological structure of the subsurface of the Moon provides valuable information on lunar evolution. Recently, Chang׳E-3 has utilized lunar penetrating radar (LPR), which is equipped on the lunar rover named as Yutu, to detect the lunar geological structure in Northern Imbrium (44.1260N, 19.5014W) for the first time. As an in situ detector, Chang׳E-3 LPR has relative higher horizontal and vertical resolution and less clutter impact compared to spaceborne radars and earth-based radars.In this work, we analyze the LPR data at 500MHz transmission frequency to obtain the shallow subsurface structure of the landing area of Chang׳E-3 in Mare Imbrium. Filter method and amplitude recovery algorithms are utilized to alleviate the adverse effects of environment and system noises and compensate the amplitude losses during signal propagation. Based on the processed radar image, we observe numerous diffraction hyperbolae, which may be caused by discrete reflectors beneath the lunar surface. Hyperbolae fitting method is utilized to reverse the average dielectric constant to certain depth (ε¯). Overall, the estimated ε¯ increases with the depth and ε¯ could be classified into three categories. Average ε¯ of each category is 2.47, 3.40 and 6.16, respectively. Because of the large gap between the values of ε¯ of neighboring categories, we speculate a three-layered structure of the shallow surface of LPR exploration region.One possible geological picture of the speculated three-layered structure is presented as follows. The top layer is weathered layer of ejecta blanket with its average thickness and bound on error is 0.95±0.02m. The second layer is the ejecta blanket of the nearby impact crater, and the corresponding average thickness is about 2.30±0.07m, which is in good agreement with the two primary models of ejecta blanket thickness as a function of distance from the crater center. The third layer is regarded as a mixture of stones and soil. The echoes below the third layer are in the same magnitude as the noises, which may indicate that the fourth layer, if it exists, is uniform (no clear reflector) and its thickness is beyond the detection limit of LPR. Hence, we infer the fourth layer is a basalt layer.

Astrometric Support for the Lunar-based Ultraviolet Telescope

The Lunar-based Ultraviolet Telescope (LUT) is an astronomical instrument aboard Chang’e 3, the lunar probe of China’s Lunar Exploration Program that successfully landed on the northern part of the Moon’s Mare Imbrium (340.4884E, 44.1214N) in late 2013. LUT is charting an ultraviolet map of the plane of the Milky Way and is also providing long-term light variability monitoring for a sample of RR Lyrae stars. However, the principal goal of the computer-controlled landing of the probe was a safe descent to a stable resting-place, and therefore, the precise orientation of LUT was never a priority. For this reason, at least theoretically, touch-down could have occurred anywhere and, for LUT, at any attitude, which would make the pointing and tracking of the wanted celestial objects practically impossible. Moreover, to reduce the data transmission load, the whole frame of every exposure could not be downloaded: only the image data containing the objects can make it to the ground; also, in order to save on electricity, the telescope does not usually track objects, which means that targets’ accurate positions and velocities (within the focal plane CCD) are both needed. This paper presents the astrometric solution devised to solve these problems: feasibility is first shown with experiments done from Earth, and then confirmed with actual LUT observations from the Moon’s surface.

In situ optical measurements of Chang'E-3 landing site in Mare Imbrium: 2. Photometric properties of the regolith

The panorama cameras onboard the Yutu Rover of the Chang'E-3 lunar mission acquired hundreds of high-resolution color images of the lunar surface and captured the first in situ lunar opposition effect (OE) since the Apollo era. We extracted the phase curve and the color ratio in three bands with the phase angle range from 2 degrees to 141 degrees. Photometric inversions using the Hapke model reveal that submicroscopic dusts are present in the landing area and both the coherent backscattering and the shadow hiding are responsible for the strong OE. Compared with spaceborne measurements, the grains in the landing site are brighter, more transparent, and appear to be better crystallized than the average maria basaltic grains. The results show that the phase-reddening effect appears to be present in the in situ phase curves. The current phase curve can be used as the ground-truth validations of any future spaceborne phase curve measurement over the landing site region.

In situ optical measurements of Chang'E‐3 landing site in Mare Imbrium: 1. Mineral abundances inferred from spectral reflectance

AbstractThe visible and near‐infrared imaging spectrometer on board the Yutu Rover of Chinese Chang'E‐3 mission measured the lunar surface reflectance at a close distance (~1 m) and collected four spectra at four different sites. These in situ lunar spectra have revealed less mature features than that measured remotely by spaceborne sensors such as the Moon Mineralogy Mapper instrument on board the Chandrayaan‐1 mission and the Spectral Profiler on board the Kaguya over the same region. Mineral composition analysis using a spectral lookup table populated with a radiative transfer mixing model has shown that the regolith at the landing site contains high abundance of olivine. The mineral abundance results are consistent with that inferred from the compound measurement made by the on board alpha‐particle X‐ray spectrometer.

Reflectance calibration and shadow effect of VNIS spectra acquired by the Yutu rover

Yutu is the first lunar rover after the Apollo program and Luna missions. One of the payloads on the Yutu rover, the Visible and Near-infrared Imaging Spectrometer (VNIS), has acquired four VIS/NIR images and SWIR spectra near its landing site in Mare Imbrium. The radiance images were reduced through repairing bad lines and bad points, and applying flat field correction, and then were converted into reflectance values based on the solar irradiance and angles of incidence. A significant shadow effect was observed in the VIS/NIR image. The shadowed regions show lower reflectance with a darkening trend compared with illuminated regions. The reflectance increased by up to 24% for entire images and 17% for the VIS/NIR-SWIR overlapping regions after shadow correction. The correction for the shadow effect will remarkably decrease the estimate of FeO content, by up to 4.9 wt.% in this study. The derived FeO contents of CD-005∼008 after shadow correction are around 18.0 wt.%.

Geologic characteristics of the Luna 17/Lunokhod 1 and Chang'E-3/Yutu landing sites, Northwest Mare Imbrium of the Moon

We compared and assessed the results of measurements and observations by the Lunokhod 1 and Yutu rovers, both of which explored the northwestern part of Mare Imbrium. Both sites are within the distinctive Eratosthenian-aged lava flow geologic unit and our comparisons showed that the geologies of these exploration sites are very similar. As in the majority of other areas of the Moon, the dominant landforms in these sites are small impact craters, having various degrees of morphologic prominence and states of preservation, and rock fragments, mostly associated with the rims and interiors of fresh craters. The shape and the degree of preservation of the observed rock fragments in these two sites are similar. In both sites sporadic rock fragments were observed whose morphologies suggest that their source rocks had columnar jointing. Localization of these specific rocks on the rims of 450–470m in diameter craters implies that the source rocks are at depths of 40–50m. Regolith in the study areas is typically a few meters thick, but locally can be much thicker. The ground penetrating radar of the Yutu rover revealed the multilayer regolith structure, which is determined by superposition of crater ejecta; with some local variations, this type of the regolith stratigraphy should be typical of the majority of lunar mare sites. The physico-mechanical properties of the regolith in these two sites appear to be rather similar: the bearing capacity ranges from 0.04 to 1.44kg/cm2, with a modal value ∼0.45kg/cm2, and the shear strength ranges from 0.02 to 0.1kg/cm2, with a modal value ∼0.05kg/cm2. Both these factors decrease by a factor of 3–4 with an increase of surface slope from ∼2 to 12°. The chemical composition of surface materials determined by the rover instruments at these two sites differ from those derived from the remote sensing data for the Eratosthenian-aged basalts on which the two sites are located. This could be partly due to low measurement accuracies, especially in the case of Lunokhod 1, but may also represent real variations in the composition of the surface materials compared to returned lunar samples. Difference in the spatial resolution of the in-situ and remote-sensing analyses should also be taken into account. Recommendations for future lunar rover missions are as follows: (1) to use ground penetrating radar and a robotic arm, and (2) to employ radial study tactics for impact crater documentation and analysis.

Estimation of lunar major elemental abundances in Chang’E-3 landing site based on Active Particle-induced X-ray Spectrometer (APXS)

Elemental abundance provides an effective vehicle to understand lunar petrologic characteristics and evolutional history. The APXS mounted on the Yutu rover provides a valuable opportunity to determine the major elemental abundances in lunar soil within a short distance. In this study, we processed the APXS spectra including energy calibration, dead time correction and nonlinear least-squares fitting, and determined the abundances of the lunar major elements using the fundamental parameter method. In the calculation of X-ray fluorescence yield, a finite element method (FEM) was employed to improve the accuracy. The major elemental abundances derived from Chang’E-3 (CE-3) APXS possess a good consistency with the result of LP-GRS (Lunar Prospector gamma-ray spectrometer) data in the landing region. Compared with the chemical composition of the returned lunar rock samples, we draw the conclusion that the lunar soils in CE-3 landing site are fragments of mare basalts. Our conclusion is supported by the geological map of Mare Imbrium.

Relative position determination between Chang’E-3 lander and rover using in-beam phase referencing

Chang’E-3 is China’s first lunar surface exploration mission, as a part of the second phase of China’s Lunar Exploration Program (CLEP). It landed successfully in the northwest of Mare Imbrium on December 14, 2013, incorporating two probes, a lander and a rover named Yutu. The execution of the cooperative science tasks required an accurate determination of the relative position between the lander and the rover. In-beam phase referencing experiments have been conducted with the Chinese VLBI Network (CVN) to accurately image the rover in reference to the stationary lander in order to obtain their offsets in Right Ascension and Declination, which were then transformed into the lunar local coordinate system to acquire their relative position on the lunar surface. The observations and the data processing procedures are described in this paper. Images of the rover in six epochs between December 15 and 21, 2013 were made, resulting in accurate positions of the rover that are consistent with the visual localization approach. Through measurement of the locations of the rover’s omnidirectional antenna with respect to the lander’s directional antenna before their separation, and the recognition of the rover’s turning actions during its exploratory moves, we demonstrate that the accuracy of relative position determined in this way could reach the meter level and the resolution is better than 1 meter.

Yutu rover reveals subsurface structure of the Moon

Chinese lunar mission Chang’E-3 is the latest in-situ exploration to the Moon after the Apollo and Luna missions finished 40 years ago. It is composed of a lander and a rover (Yutu: named after the jade rabbit on the Moon in a Chinese fairy tale). Yutu rover is equipped with several scientific instruments including a lunar penetrating radar (LPR), whose measurement has never been carried out on a rover. After integrating the LPR data with other in-situ and geological informations, Xiao et al. [1] discovered several subsurface layers in northern Mare Imbrium, which reveals a much more complex geological history than previous thought. The surface of the landing site is within the Eratosthenian materials [2], which is younger than those of the Apollo and Luna landing sites. In the landing area, impact craters with different sizes and degradations were observed. Among the fresh ejecta deposits, a ~4 m long, ~1.5 m high boulder (Loong Rock) is of particular interest. It looks homogeneous with the ~1.5 to 2 cm light color crystals in high resolution images taken by Panoramic Camera, and it is distinct in texture from the samples obtained by the Apollo missions. The most significant advance is the subsurface structure revealed by LPR (Figure 1). LPR has two channels (Channel 1: 60 MHz and Channel 2: 500 MHz), which were designed to detect subsurface layers with different depths and resolutions [3]: Channel 1 radar can disclose subsurface interface deep to ~400 m, while Channel 2 radar can “see” depth shallower than 12 m but with greater detail. LPR observed the interface of Eratosthenian and Imbrian, which is consistent with the thickness of Eratosthenian determined by impact crater [4]. In addition, several layers of paleoregolith were also detected, and they demonstrated the existence of intervals of different volcanic eruptions and subsequent space weathering processes. These thicknesses of the paleoregolith layers could help us understand the rate variations of space weathering through time. Besides the paleoregolith layers, LPR discovered several distinct layers that could be composed of pyroclastic materials. They revealed the changes of eruption style during emplacement of the Imbrian volcanic materials. Several questions still need to be addressed in future study: 1) What were the conditions forming the coarsegrained Loong Rock? 2) What were the rates of space weathering in the Imbrian and what were the reasons for the rate variations? 3) What were the key elements controlling the changes of volcanic eruption and/or overflow style?

Retrieval of the bulk density of lunar subsurface layer from diurnal differences of Chang′E-2 microwave and LRO infrared brightness temperature data

Comparisons of microwave brightness temperature (TB) observed by Chang′E-1 and Chang′E-2 with FeO+TiO2 content observed by Clementine indicate a correspondence of diurnal difference of microwave TB to FeO+TiO2 content in distribution, especially for 37GHz. The correlation of FeO+TiO2 content and 37GHz TB is discussed. Consequently, we choose the regions, e.g. (30°N, 25°W) in Mare Imbrium and (30°N, 55°W) in Oceanus Procellarum of uniform FeO+TiO2 content for further studying the bulk density of lunar subsurface layer, avoiding the interference of FeO and TiO2. The lunar surface is regarded as a two-layer model. According to the infrared TB observed by LRO which is approximately equal to lunar surface temperature, it is found that the thermophysical properties of the lunar upper surface layer appear uniform for the sampled regions. In that way, distinct diurnal differences of microwave TB in both regions are related to the bulk density of lunar subsurface layer. A theoretical analysis based on a two-layer microwave TB model confirms the correlation between diurnal differences of microwave TB and bulk density of lunar subsurface layer. Finally, the bulk density of lunar subsurface layer is retrieved from microwave TB observed by Chang′E-2, ranging from 1.90 to 2.04g/cm3 for a profile at 33°N extending from 120°W to 6°E.

The Chang’e 3 Mission Overview

The Chang’e 3 (CE-3) mission was implemented as the first lander/rover mission of the Chinese Lunar Exploration Program (CLEP). After its successful launch at 01:30 local time on December 2, 2013, CE-3 was inserted into an eccentric polar lunar orbit on December 6, and landed to the east of a 430 m crater in northwestern Mare Imbrium (19.51°W, 44.12°N) at 21:11 on December 14, 2013. The Yutu rover separated from the lander at 04:35, December 15, and traversed for a total of 0.114 km. Acquisition of science data began during the descent of the lander and will continue for 12 months during the nominal mission. The CE-3 lander and rover each carry four science instruments. Instruments on the lander are: Landing Camera (LCAM), Terrain Camera (TCAM), Extreme Ultraviolet Camera (EUVC), and Moon-based Ultraviolet Telescope (MUVT). The four instruments on the rover are: Panoramic Camera (PCAM), VIS-NIR Imaging Spectrometer (VNIS), Active Particle induced X-ray Spectrometer (APXS), and Lunar Penetrating Radar (LPR). The science objectives of the CE-3 mission include: (1) investigation of the morphological features and geological structures of and near the landing area; (2) integrated in-situ analysis of mineral and chemical composition of and near the landing area; and (3) exploration of the terrestrial-lunar space environment and lunar-based astronomical observations. This paper describes the CE-3 objectives and measurements that address the science objectives outlined by the Comprehensive Demonstration Report of Phase II of CLEP. The CE-3 team has archived the initial science data, and we describe data accessibility by the science community.

Volcanic history of the Imbrium basin: A close-up view from the lunar rover Yutu

We report the surface exploration by the lunar rover Yutu that landed on the young lava flow in the northeastern part of the Mare Imbrium, which is the largest basin on the nearside of the Moon and is filled with several basalt units estimated to date from 3.5 to 2.0 Ga. The onboard lunar penetrating radar conducted a 114-m-long profile, which measured a thickness of ∼5 m of the lunar regolith layer and detected three underlying basalt units at depths of 195, 215, and 345 m. The radar measurements suggest underestimation of the global lunar regolith thickness by other methods and reveal a vast volume of the last volcano eruption. The in situ spectral reflectance and elemental analysis of the lunar soil at the landing site suggest that the young basalt could be derived from an ilmenite-rich mantle reservoir and then assimilated by 10-20% of the last residual melt of the lunar magma ocean.

A young multilayered terrane of the northern Mare Imbrium revealed by Chang'E-3 mission.

China's Chang'E-3 (CE-3) spacecraft touched down on the northern Mare Imbrium of the lunar nearside (340.49°E, 44.12°N), a region not directly sampled before. We report preliminary results with data from the CE-3 lander descent camera and from the Yutu rover's camera and penetrating radar. After the landing at a young 450-meter crater rim, the Yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders. The boulder contains a substantial amount of crystals, which are most likely plagioclase and/or other mafic silicate mineral aggregates similar to terrestrial dolerite. The Lunar Penetrating Radar detection and integrated geological interpretation have identified more than nine subsurface layers, suggesting that this region has experienced complex geological processes since the Imbrian and is compositionally distinct from the Apollo and Luna landing sites.