Space Weathering Age of Itokawa and Eros by Machine LearningOPEN ACCESS 

Lakshika Palamakumbure, David Korda and Tomáš Kohout

The Planetary Science Journal, Volume 7, Number 3, Published: 17 March 2026

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“Near-Earth asteroids such as Itokawa and Eros provide valuable insights into the collisional and surface evolution of the inner solar system. As S-type asteroids, their surfaces are altered by space weathering (SW) from solar wind and micrometeorite impacts. Because SW progresses over time, it serves as a proxy for estimating surface exposure ages, revealing resurfacing and geologic histories. This study estimates the SW ages at the present conditions of Itokawa and Eros using a machine learning model developed by L. Palamakumbure et al. The ensemble model was trained on laboratory reflectance spectra of irradiated silicate samples (olivine, pyroxene, mixtures, and chondrites) to capture spectral changes due to SW. Asteroid spectra were obtained from the Near Infrared Spectrometer (Hayabusa) dataset for Itokawa and the Near-Infrared Spectrometer (NEAR Shoemaker) dataset for Eros via NASA Planetary Data System. SW ages for Itokawa range from 1.9 kyr to 2.5 Gyr, reflecting alteration from both solar wind and micrometeorite impacts. Eros, in contrast, shows older SW ages (0.4 to 2 Gyr), dominated by micrometeorite effects. These results align with previous studies and Hayabusa sample analyses, confirming Itokawa’s young surfaces are influenced by solar wind, with older, less disturbed regions such as Arcoona. Eros displays more uniformly mature surfaces, with localized relatively young areas linked to cratering or regolith movement. The contrasting SW ages highlight how asteroid size, regolith behavior, and orbital characteristics influence SW processes. Overall, the study demonstrates the potential of machine learning for reconstructing surface exposure histories on airless bodies.”