This study explores the impact of granular materials with varying moisture contents and particle sizes, as well as block materials with different volumes and layer strengths, on landslide fragmentation, motion, and deposit. The experimental results show that as particle size increases, the maximum dam height (Hmax) and width (Wmax) increase, while the minimum dam height (Hmin) decreases, indicating an improvement in the stability of landslide dams. Larger particle sizes are less sensitive to changes in moisture content. Additionally, moisture content inhibits Wmax, with mixed particle-size materials showing a greater reduction compared to single particle-size materials. As Wmax increases, the maximum dam length (Lmax) decreases exponentially. Sliding time (Ts), deposition time (Td), and total time (T) decrease as particle size increases. For mixed particle-size materials, a more continuous particle size distribution further reduces Ts, Td, and T. Block material experiments show that with increasing block volume, Wmax, Lmax, and Hmax increase significantly, with corresponding increases in Ts, Td, and T. When the strength of the lower layer material decreases, Wmax and Hmax decrease, while Ts, Td, and T increase. Conversely, when the lower layer material strength increases, the opposite effect is observed. Frictional energy loss (Ef) is the primary energy loss pathway, with both total energy loss and Efdecreasing with increasing particle size. Localized energy losses are mainly due to terrain collisions, independent of moisture content.

Observations of widespread hydration across the lunar surface could be attributed to water formed via the implantation of solar wind hydrogen ions into minerals at the surface. Solar wind irradiation produces a defectrich outer rim in lunar regolith grains which can trap implanted hydrogen to form and store water. However, the ability of hydrogen and water to be retained in space weathered regolith at the lunar surface is not wellunderstood. Here, we present results of novel and coordinated high-resolution analyses using transmission electron microscopy and atom probe tomography to measure hydrogen and water within space weathered lunar grains. We find that hydrogen and water are present in the solar wind-damaged rims of lunar grains and that these species are stored in higher concentrations in the vesicles that are formed by solar wind irradiation. These vesicles may serve as reservoirs that store water over diurnal and possibly geologic timescales. Solar windderived water trapped in space weathered rims is likely a major contributor to observations of the widespread presence, variability, and behavior of the water across the lunar surface.

The impact of water droplets on soils has recently been found to drive emissions of airborne soil organic particles (ASOP). The chemical composition of ASOP include macromolecules such as polysaccharides, tannins, and lignin (derived from degradation of plants and biological organisms), which determine light absorbing (brown carbon) particle properties. Optical properties of ASOP were inferred from the quantitative analysis of the electron energy-loss spectra acquired over individual particles using transmission electron microscopy. The optical constants of ASOP are compared with those measured for laboratory generated particles composed of Suwanee River Fulvic Acid (SRFA) reference material, which is used as a laboratory surrogate of ASOP. The chemical composition of the particles was analyzed using energy dispersive X-ray spectroscopy, electron energy-loss spectroscopy, and synchrotron-based scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy. ASOP and SRFA exhibit similar carbon composition, with minor differences in other elements present. When ASOP are heated to 350 degrees C their absorption increases as a result of pyrolysis and partial volatilization of semivolatile organic constituents. The retrieved refractive index (RI) at 532 nm of SRFA particles, ASOP, and heated ASOP were 1.22-0.07i, 1.29-0.07i, and 1.90-0.38i, respectively. Retrieved imaginary part of the refractive index of SRFA particles derived from EELS measurements was higher and the real part was lower compared to data from more common optical methods. Therefore, corrections to the EELS data are needed for incorporation into models. These measurements of ASOP optical constants confirm that they have properties characteristic of atmospheric brown carbon and therefore their potential effects on the radiative forcing of climate need to be assessed in atmospheric models.