RESUMO
Yutu-2 rover conducted an exciting expedition on the 41st lunar day to investigate a fin-shaped rock at Longji site (45.44°S, 177.56°E) by extending its locomotion margin on perilous peaks. The varied locomotion encountered, especially multi-form wheel slippage, during the journey to the target rock, established unique conditions for a fin-grained lunar regolith analysis regarding bearing, shear and lateral properties based on terramechanics. Here, we show a tri-aspect characterization of lunar regolith and infer the rock's origin using a digital twin. We estimate internal friction angle within 21.5°-42.0° and associated cohesion of 520-3154 Pa in the Chang'E-4 operational site. These findings suggest shear characteristics similar to Apollo 12 mission samples but notably higher cohesion compared to regolith investigated on most nearside lunar missions. We estimate external friction angle in lateral properties to be within 8.3°-16.5°, which fills the gaps of the lateral property estimation of the lunar farside regolith and serves as a foundational parameter for subsequent engineering verifications. Our in-situ spectral investigations of the target rock unveil its composition of iron/magnesium-rich low-calcium pyroxene, linking it to the Zhinyu crater (45.34°S, 176.15°E) ejecta. Our results indicate that the combination of in-situ measurements with robotics technology in planetary exploration reveal the possibility of additional source regions contributing to the local materials at the Chang'E-4 site, implying a more complicated geological history in the vicinity.
RESUMO
The experimentally observed planar hypercoordinate carbon species were detected in gas phase experiments and characterized by photoelectron spectroscopy. According to the Boltzmann distribution law, the thermodynamically favorable isomers, especially global minima, were relatively easier to detect than other isomers in such an experimental process. Here, we reported a thermodynamically unfavorable case, i.e., D3h CN3Mg3(+) (1a), which we think is experimentally viable because all isomers that are energetically lower than 1a show bimolecular assembly type structures consisting of an N2 unit and various types of CNMg3(+) units. The natural bond orbital (NBO) analysis suggests that the bonding between N2 and CNMg3(+) is rather weak, and we think it is very hard to retain their basic structures when kinetic factors are considered. Consistently, the four lowest isomers in the second group show dissociation (to free N2 molecule and CNMg3(+) cations) during Born-Oppenheimer molecular dynamic (BOMD) simulations. In contrast, the structure of 1a can be maintained under temperatures up to 2000 K during the BOMD simulation, and ring-opening reaction studies suggest the barrier to be very high, 46.75 kcal/mol. We think the excellent kinetic stability of 1a will compensate for its thermodynamic instability and it will own its existence in the gas phase synthesis. Although many isomers in the second group are energetically more favorable than 1a, they will be dissociated by the kinetic process. In the magnetic field, the positively charged CNMg3(+) units will be separated quickly from N2 molecules in the general gas phase synthesis, and they are therefore undetectable.
