Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors
Trans-Neptunian objects (TNOs) exhibit a color diversity containing a wealth of clues for understanding complex compositions and the formation history of our solar system. The origin of this wide color distribution is still uncertain, but it is likely due to surface ice exposed to ionizing radiation...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4365/adc718 |
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| author | Chaojiang Zhang Jia Wang Andrew M. Turner Leslie A. Young Ralf I. Kaiser |
| author_facet | Chaojiang Zhang Jia Wang Andrew M. Turner Leslie A. Young Ralf I. Kaiser |
| author_sort | Chaojiang Zhang |
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| description | Trans-Neptunian objects (TNOs) exhibit a color diversity containing a wealth of clues for understanding complex compositions and the formation history of our solar system. The origin of this wide color distribution is still uncertain, but it is likely due to surface ice exposed to ionizing radiation at various levels. Here, we present the spectroscopic evolution of visible reflectance, spectral slopes, and colors from TNO surface ice analogs processed by Galactic cosmic-ray proxy. This study provides compelling evidence that irradiated carbon-containing molecular ices show notable reddening in their visible reflectance spectra. The spectral slopes of processed water ices are neutral and independent of the radiation dose, whereas those of ammonia decrease with the increasing radiation dose. When the carbon-containing molecules are mixed with water and ammonia, the reddening process is found to be neutralized. The irradiation experiments at different temperatures demonstrate that the irradiation temperature could control the reddening efficiency of ices containing carbon and oxygen. For example, the color slopes of pure methanol and carbon dioxide ices significantly increase when the irradiation temperature is 40 K, but there is almost no change at 10 K. This indicates that the color diversity of TNOs can be influenced not only by different levels of radiation exposure but also by varying irradiation temperatures. The data in the current study provide new insights into the influence of initial composition, radiation dose, and irradiation temperature on the color diversity of TNOs, which supply important information for cataloging their surface compositions. |
| format | Article |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-90e4d9deccec49ca9a911bd142ae171f2025-08-20T03:52:42ZengIOP PublishingThe Astrophysical Journal Supplement Series0067-00492025-01-0127813010.3847/1538-4365/adc718Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and ColorsChaojiang Zhang0https://orcid.org/0000-0003-3727-901XJia Wang1https://orcid.org/0000-0002-3795-8699Andrew M. Turner2Leslie A. Young3https://orcid.org/0000-0002-7547-3967Ralf I. Kaiser4https://orcid.org/0000-0002-7233-7206Department of Chemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USA ; ralfk@hawaii.edu; W. M. Keck Laboratory in Astrochemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USADepartment of Chemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USA ; ralfk@hawaii.edu; W. M. Keck Laboratory in Astrochemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USADepartment of Chemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USA ; ralfk@hawaii.edu; W. M. Keck Laboratory in Astrochemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USADepartment of Space Studies, Southwest Research Institute , Boulder, CO 80302, USA ; layoung@boulder.swri.eduDepartment of Chemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USA ; ralfk@hawaii.edu; W. M. Keck Laboratory in Astrochemistry, University of Hawaii at Mānoa , Honolulu, HI 96822, USATrans-Neptunian objects (TNOs) exhibit a color diversity containing a wealth of clues for understanding complex compositions and the formation history of our solar system. The origin of this wide color distribution is still uncertain, but it is likely due to surface ice exposed to ionizing radiation at various levels. Here, we present the spectroscopic evolution of visible reflectance, spectral slopes, and colors from TNO surface ice analogs processed by Galactic cosmic-ray proxy. This study provides compelling evidence that irradiated carbon-containing molecular ices show notable reddening in their visible reflectance spectra. The spectral slopes of processed water ices are neutral and independent of the radiation dose, whereas those of ammonia decrease with the increasing radiation dose. When the carbon-containing molecules are mixed with water and ammonia, the reddening process is found to be neutralized. The irradiation experiments at different temperatures demonstrate that the irradiation temperature could control the reddening efficiency of ices containing carbon and oxygen. For example, the color slopes of pure methanol and carbon dioxide ices significantly increase when the irradiation temperature is 40 K, but there is almost no change at 10 K. This indicates that the color diversity of TNOs can be influenced not only by different levels of radiation exposure but also by varying irradiation temperatures. The data in the current study provide new insights into the influence of initial composition, radiation dose, and irradiation temperature on the color diversity of TNOs, which supply important information for cataloging their surface compositions.https://doi.org/10.3847/1538-4365/adc718Trans-Neptunian objectsIce spectroscopySurface ices |
| spellingShingle | Chaojiang Zhang Jia Wang Andrew M. Turner Leslie A. Young Ralf I. Kaiser Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors The Astrophysical Journal Supplement Series Trans-Neptunian objects Ice spectroscopy Surface ices |
| title | Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors |
| title_full | Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors |
| title_fullStr | Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors |
| title_full_unstemmed | Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors |
| title_short | Spectroscopic Evolution in Ice Analogs of Trans-Neptunian Objects Exposed to Ionizing Radiation. I. Visible Reflectance Spectra and Colors |
| title_sort | spectroscopic evolution in ice analogs of trans neptunian objects exposed to ionizing radiation i visible reflectance spectra and colors |
| topic | Trans-Neptunian objects Ice spectroscopy Surface ices |
| url | https://doi.org/10.3847/1538-4365/adc718 |
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