Technology enabled science: investigation of a fin-shaped rock by the Yutu-2 rover on the lunar farside

Abstract

Technology advancement in modern planetary exploration has extended extraterrestrial geological science by sending rovers on challenging, possibly risky but highly scientific-valuable ventures, such as ascending towards the crater walls, traversing steep slopes of sand dunes and travelling through the lava tube. On the 41st lunar day, the first lunar farside prospector, the Yutu-2 rover, carried out an exciting expedition towards a scientifically interesting fin-shaped rock for spectral investigation, taking a high risk of wheel skidding and lateral slippage along a narrow and uneven passage. The rover successfully achieved new findings by extending its locomotion margin on perilous peaks, while its safety was maintained on the basis of ingenious exploration strategies and digital twin-based performance analysis. Surface morphology analysis of the fin-shaped rock indicates that it has suffered certain degrees of impacts. The further in situ spectral investigations suggest that the target rock is composed of Fe/Mg-rich low-Ca pyroxene, thus inferred to belongs to the Zhinyu crater ejecta, rather than those of the Finsen crater. Engineering locomotive data of the rover was used for comprehensive lunar regolith property identification, presenting the first shear parameter range of the farside regolith and an initial estimation on its lateral property in the extraterrestrial environment. The estimated internal friction angle is within 21.5°-42.0° and the associated cohesion is 520-3154 Pa, which suggests that the lunar regolith at Chang’E-4 site had similar shear characteristics to samples measured by direct shear approach on the Apollo 12 mission, but relatively larger cohesion than the counterpart investigated on most of nearside lunar missions. This study demonstrates a paradigm of the in-depth integration of science and technology in space exploration, where planetary science is enabled by engineering support, and new demands of scientific exploration in turn generate motivation for the improvement of technology.