Masaki Nishino

The Multi-Band Camera (MBC) on board the Smart Lander for Investigating Moon (SLIM) was designed for high-resolution near-infrared imaging of lunar rocks, achieving a spatial resolution of 1.1mm per pixel from a distance of 10 meters. A standout feature of MBC is its capacity to estimate the olivine Mg♯ (Mg/(Mg+Fe)) using 10 band-pass filters covering wavelengths from 750 to 1650nm. The instrument incorporates an auto-focus system, a movable mirror mechanism, and a specialized spectral observation framework, representing a substantial advancement in lunar surface exploration. Despite the unanticipated landing attitude of SLIM, MBC successfully performed numerous scans, acquiring near-infrared images with unprecedented spatial resolution. These observations represent a significant breakthrough in lunar exploration technology, marking a major advancement in surface analysis capabilities. The techniques and knowledge gained will serve as valuable resources for future endeavors, such as the forthcoming LUPEX mission.

Smart Lander for Investigating Moon (SLIM), a small spacecraft with a dry mass of 200kg, was launched on September 7, 2023 by the H-IIA rocket and made a pinpoint Moon landing on January 19, 2024 (UTC). Precise landing performance was evaluated to be approximately 10 meters or less, much better that the target landing accuracy of 100 meters, realizing the world's first pinpoint landing. This paper describes the design and manufacturing results including its compact and lightweight technology, and operational results of the SLIM.

Abstract The density of the solar wind plasma near the Earth’s magnetosphere sometimes decreases to only several per cent of the usual value, and such density extrema result in a significant reduction of the dynamic pressure and Alfvén Mach number ($$M_A$$) of the solar wind flow. While a symmetric expansion of the Earth’s magnetosphere by the low dynamic pressure was assumed in previous studies, a global magnetohydrodynamic (MHD) simulation study predicted a remarkable dawn-dusk asymmetry of the magnetospheric shape under low-density solar wind and Parker-spiral interplanetary magnetic field (IMF) configuration. Here, we present observations consistent with the asymmetric deformation of the magnetosphere under low-$$M_A$$ solar wind and Parker-spiral IMF conditions, focusing on the significant expansion of the dawn-flank magnetosphere detected by the Geotail spacecraft. A global MHD simulation reproduced the dawnward expansion of the near-Earth magnetosphere, which was consistent with the observation by Geotail. The solar wind flow had a non-negligible dusk-to-dawn component and partly affected the dawnward expansion of the magnetosphere. Local, roughly Alfvénic sunward acceleration of magnetosheath ions at the dawn flank magnetopause suggests magnetosheath plasma entry into the magnetosphere through open field lines generated by magnetic reconnection at the dayside magnetopause. At the same time, Cluster 1 and 3, located near the southern polar cusp, also detected continuous antisunward ion jets and occasional sunward jets, which are consistent with the occurrence of magnetic reconnection near the southern cusp. These observations suggest that enhanced plasma acceleration at the dayside magnetopause operates under the low-$$M_A$$ solar wind and Parker spiral IMF conditions and that plasma influx across the dawnside magnetopause is at work under such a low-$$M_A$$ condition. These results can be helpful in understanding interactions between low-$$M_A$$ solar/stellar winds and celestial objects, such as inner planets and exoplanets. Graphic Abstract

The Moon and Mercury are airless bodies, thus they are directly exposed to the ambient plasma (ions and electrons), to photons mostly from the Sun from infrared range all the way to X-rays, and to meteoroid fluxes. Direct exposure to these exogenic sources has important consequences for the formation and evolution of planetary surfaces, including altering their chemical makeup and optical properties, and generating neutral gas exosphere. The formation of a thin atmosphere, more specifically a surface bound exosphere, the relevant physical processes for the particle release, particle loss, and the drivers behind these processes are discussed in this review.