9:00 AM - 9:15 AM
[PPS08-01] Characteristics of Rocks Observed by the Multi-Band Camera (MBC) Onboard the Lunar Lander SLIM
Keywords:lunar exploration, moon landing, near-infrared spectroscopy
The Smart Lander for Investigating Moon (SLIM), a small-scale lunar lander demonstrator, was launched on September 7, 2023, and successfully achieved the world’s first pinpoint landing on the Moon on January 20, 2024. The landing site is located near Shioli Crater (13.3°S, 25.2°E), southwest of the rim of Theophilus Crater. Using the Multi-Band Camera (MBC) onboard SLIM, we observed rocks around the landing site and estimated their origins.
MBC is equipped with high spatial resolution (1.1 mm/pixel at a distance of 10 m) for rock type identification and a 10-band bandpass filter (750, 920, 950, 970, 1000, 1050, 1100, 1250, 1550, and 1650 nm) for mineral identification and estimation of the Mg/Fe ratio in olivine. Additionally, the movable mirror mechanism allows for adjustments in the azimuth and elevation angles of the field of view.
Using MBC, we selected 10 large rocks in the surrounding area and conducted 10-band spectral observations. From the acquired 10-band imaging data, reflectance images were generated. To reduce the effects of space weathering, the reflectance values were normalized by dividing by the continuum reflectance, defined as the straight-line reflectance connecting 750 nm and 1550 nm. Using these continuum-normalized reflectance values, we generated an RGB composite image by assigning the absorption depths at 950 nm, 1050 nm, and 1250 nm to the red, green, and blue intensities of each pixel, respectively. Additionally, a spline fit was applied to the continuum-removed reflectance, and for each pixel, the wavelength at which the lowest reflectance occurred in the 800–1400 nm range—corresponding to the absorption peak—was searched to generate an absorption peak wavelength map.
By analyzing these two images and additionally examining the reflectance spectra for the presence or absence of spectral downturns toward the 2 micron-absorption peak of pyroxene, we identified the constituent minerals and lithologies of each rock. The examination of spectral downturns was particularly useful for distinguishing between high-Ca pyroxene and olivine in ambiguous cases.
Although some of the observed rocks were affected by brecciation, the parent lithologies of these breccias can be broadly classified into anorthosite, norite, lherzolite, and dunite. These rock types are consistent with those expected to be distributed from the lunar crust down to approximately 300 km depth following mantle overturn, suggesting that the observed rock variations reflect the lithological diversity at certain depths in this region.
MBC is equipped with high spatial resolution (1.1 mm/pixel at a distance of 10 m) for rock type identification and a 10-band bandpass filter (750, 920, 950, 970, 1000, 1050, 1100, 1250, 1550, and 1650 nm) for mineral identification and estimation of the Mg/Fe ratio in olivine. Additionally, the movable mirror mechanism allows for adjustments in the azimuth and elevation angles of the field of view.
Using MBC, we selected 10 large rocks in the surrounding area and conducted 10-band spectral observations. From the acquired 10-band imaging data, reflectance images were generated. To reduce the effects of space weathering, the reflectance values were normalized by dividing by the continuum reflectance, defined as the straight-line reflectance connecting 750 nm and 1550 nm. Using these continuum-normalized reflectance values, we generated an RGB composite image by assigning the absorption depths at 950 nm, 1050 nm, and 1250 nm to the red, green, and blue intensities of each pixel, respectively. Additionally, a spline fit was applied to the continuum-removed reflectance, and for each pixel, the wavelength at which the lowest reflectance occurred in the 800–1400 nm range—corresponding to the absorption peak—was searched to generate an absorption peak wavelength map.
By analyzing these two images and additionally examining the reflectance spectra for the presence or absence of spectral downturns toward the 2 micron-absorption peak of pyroxene, we identified the constituent minerals and lithologies of each rock. The examination of spectral downturns was particularly useful for distinguishing between high-Ca pyroxene and olivine in ambiguous cases.
Although some of the observed rocks were affected by brecciation, the parent lithologies of these breccias can be broadly classified into anorthosite, norite, lherzolite, and dunite. These rock types are consistent with those expected to be distributed from the lunar crust down to approximately 300 km depth following mantle overturn, suggesting that the observed rock variations reflect the lithological diversity at certain depths in this region.