^1,4Hanwei Wu, ^2,4Qiquan Yang, ¹Yi Xu, ¹Sizhe Zhao, ¹Renrui Liu, ³Tianyi Xu, ¹Xiaoping Zhang, ¹Bohan Zhou
The Astrophysical Journal Letters, 1011, L7
Open Access Link to Article [DOI: 10.3847/2041-8213/aeb028]
¹State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau 999078, People’s Republic of China
²College of Surveying & Geo-Informatics, Tongji University, Shanghai 200092, People’s Republic of China
³Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210034, People’s Republic of China

Space weathering progressively modifies lunar surface regolith, while impact gardening and related processes redistribute weathered materials within the upper regolith, generating depth-dependent variations in maturity. Although surface maturity has been extensively investigated, its variation within the uppermost few centimeters remains insufficiently characterized. In particular, whether shallow maturity profiles differ between nearside and farside, especially at mid-to-high latitudes, has yet to be systematically examined. Here, using multisource orbital and in situ observations together with sampling-derived information, we investigate the depth-dependent distribution of shallow maturity at the Chang’e-5 (CE-5) landing site on the nearside and the Chang’e-6 (CE-6) site on the farside, both located at mid-to-high latitudes. Prelanding orbital spectra characterize the undisturbed surface, whereas in situ spectra acquired after plume-induced erosion (∼0.4/0.7 cm depth) and sampling excavation (∼3.4/3.7 cm depth) provide information on deeper layers, enabling maturity comparisons across three shallow stratigraphic horizons. Maturity indicators consistently indicate that the shallow regolith of CE-6 is more mature than that of CE-5, with the postlanding in situ spectra yielding I_s/FeO values of ∼78.13 and ∼31.40 for CE-6 and CE-5, respectively. Despite this difference in overall maturity, both sites exhibit similar depth-dependent patterns: the regolith becomes fresher with depth, showing relatively small maturity changes following plume erosion and more pronounced changes after sampling excavation. The similarity in these vertical patterns suggests broadly comparable intensities of two sites’ shallow regolith modification. These findings provide new observational constraints on the vertical distribution and evolution of shallow maturity and advance our understanding of regolith modification of CE-5 and CE-6 sites.

¹Kate Y. L. Su, ^2,3Attila Moór, ^2,3Ágnes Kóspál, ^4,5George H. Rieke, ⁴Antranik A. Sefilian, ⁵Renu Malhotra, ^5,6Ilaria Pascucci, ⁶Alan P. Jackson, ^2,3,7Péter Ábrahám, ^1,8Nicholas P. Ballering
The Astrophysical Journal, 1010, 1
Open Access Link to Article [DOI: 10.3847/1538-4357/ae88fe]
¹Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
²Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
³CSFK, MTA Centre of Excellence, Budapest, Konkoly Thege Miklós út 15-17., H-1121, Hungary
⁴Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
⁵Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA
⁶Department of Physics, Astronomy, and Geosciences, Towson University, 8000 York Road, Towson, MD, USA
⁷Department of Astrophysics, University of Vienna, Türkenschanzstr. 17, A-1180 Vienna, Austria
⁸Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706, USA

Debris disks are dusty structures around mature stars, primarily identified by infrared excesses in the stellar spectra. A subset, known as extreme debris disks (EDDs), exhibits stochastic infrared variability, believed to result from large-scale violent collisions that contribute to the formation or destruction of rocky planetary bodies. We analyze JWST and Spitzer mid-infrared spectra for 21 EDDs to investigate the connection between impact-produced dust mineralogy and the age and dynamical state of these systems during various stages of planet formation and evolution. Our findings indicate that EDDs contain significantly more optically thin, small dust grains compared to those typically seen in protoplanetary and debris disks. Predominantly submicron in size, these grains are thermally altered, as shown by their high levels of silica and crystalline silicate composition. Along with stochastic infrared variability, these features define EDDs as a subclass of debris systems where dust is generated from large collisions between Moon- and Mars-sized bodies. Our results not only provide a diagnostic information about the physical conditions of violent events during terrestrial planet formation, aiding in differentiating the complex outcomes of these impacts, but also offer a potential marker for identifying planetary systems experiencing dynamical instability.

¹Zichen Wei, ¹Hao Zhang
The Astrophysical Journal, 1010, 63
Open Access Link to Article [DOI: 10.3847/1538-4357/aea69a]
¹Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth and Planetary Sciences, China University of Geosciences, Wuhan, 430074, People’s Republic of China

We present a coordinated laboratory optical data set for three equilibrated ordinary chondrites (OCs; LL5/6, L6, and H6), including the recently witnessed Maoming fall of 2025 May 28, to investigate the coupled effects of grain size, surface structure, and simulated space weathering on their spectral, photometric, and polarimetric properties. Intact slabs and three grain-size fractions were measured in the fresh state and after two levels of pulsed-laser irradiation using Fourier-transform infrared reflectance spectroscopy, bidirectional reflectance distribution function (BRDF) measurements, and polarization phase curves. Irradiation generally produces spectral darkening, reddening, and weakening of the 1 and 2 μm absorption bands, although the degree of reddening depends on both composition and grain size. BRDF measurements reveal a systematic transition from nearly isotropic scattering in fine powders to enhanced backscattering in coarse powders and pronounced specular reflection from slabs. These scattering characteristics remain largely unchanged after irradiation, indicating that grain size and surface structure exert stronger control on angular scattering than irradiation-induced optical darkening. The specular component is strongly suppressed in the irradiated LL5/6 slab but remains evident in the L6 and especially H6 slabs, suggesting a contribution from metal-rich phases. Polarimetric measurements further show systematic differences between slabs and powders, with surface morphology influencing both the negative-polarization branch and the large-phase-angle polarization behavior. This dataset demonstrates that grain size and surface structure are as important as composition and space weathering in governing the optical properties of OCs, providing complementary constraints for interpreting OC-like asteroid surfaces.

¹Benjamin N. L. Sharkey, ²Vishnu Reddy, ³John W. Noonan, ⁴Theodore Kareta, ¹James M. Bauer, ⁵Bryan J. Holler, ¹Yaeji Kim, ⁶Albert R. Conrad
The Astrophysical Journal Letters, 1010, L31
Open Access Link to Article [DOI: 10.3847/2041-8213/aea6b6]
¹Department of Astronomy, University of Maryland College Park, MD 20742-2421, USA
²Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
³Department of Physics, Edmund C. Leach Science Center, Auburn University, Auburn, AL, USA
⁴Department of Astrophysics and Planetary Science, Villanova University, Villanova, PA, USA
⁵Space Telescope Science Institute, Baltimore, MD, USA
⁶Large Binocular Telescope Observatory, Tucson, AZ, USA

Near-Earth asteroid (469219) Kamoʻoalewa is a uniquely stable quasi-satellite of the Earth and a target of the Tianwen-2 spacecraft mission. Here we report observations taken with JWST’s NIRSpec instrument in integral field unit (IFU) mode in 2026 February. The JWST reflectance spectrum is notably less red (more neutral) from 1.0 to 2.5 μm than previous ground-based spectrophotometric observations. New observations made with the Large Binocular Telescope (LBT) in 2026 April, observed and processed similarly to the 2021 observations, find zJ colors in agreement with JWST. Kamoʻoalewa’s infrared colors appear more similar to typical silicate-rich asteroids and unlike the reddened, space-weathered lunar-like silicates suggested by previous observations. In agreement with the ground-based spectrum, we detect a faint silicate absorption feature at 0.93 ± 0.01 μm. We do not detect a 2.0 μm silicate absorption. Models of Kamoʻoalewa’s faint thermal emission (beginning near 4.5 μm) find a mean diameter of D = 18 ± 2 m and best-fit visible albedo p_V = 0.59^+0.25_−0.17, with models as low as p_V = 0.36 providing adequate model fits. This combination of color, albedo, and absorption bands is similar to oldhamite-bearing enstatite-rich compositions. Kamoʻoalewa’s brightness variations over the course of the JWST program provide independent confirmation of its rotation period of 27.9 minutes, with an axis ratio ∼1.4 (D ∼ 15–21 m).