Self-Secondaries Formed by Cold Spot Craters on the Moon
Self-secondaries are a population of background secondaries, and they have been observed on top of impact melt and ballistically emplaced ejecta deposits on various planetary bodies. Self-secondaries are formed by impacts of sub-vertically launched ejecta, but the launch mechanism is not confirmed....
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-03-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/6/1087 |
| _version_ | 1797541507130982400 |
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| author | Yiren Chang Zhiyong Xiao Yang Liu Jun Cui |
| author_facet | Yiren Chang Zhiyong Xiao Yang Liu Jun Cui |
| author_sort | Yiren Chang |
| collection | DOAJ |
| description | Self-secondaries are a population of background secondaries, and they have been observed on top of impact melt and ballistically emplaced ejecta deposits on various planetary bodies. Self-secondaries are formed by impacts of sub-vertically launched ejecta, but the launch mechanism is not confirmed. The potential threat of self-secondaries to the theoretical and applicable reliability of crater chronology has been noted, but not constrained. Hitherto discovered self-secondaries were located around complex impact craters, but their potential existence around simple craters has not been discovered. Here we report the first discovery of self-secondaries around lunar cold spot craters, which are an extremely young population of simple craters formed within the past ~1 million years on the Moon. Self-secondaries are widespread on layers of cascading flow-like ejecta deposits around cold spot craters. The spatial density of self-secondaries dwarfs that of potential primary craters. The spatial distribution of self-secondaries is highly heterogeneous across the ejecta deposits. With respect to the impactor trajectory that formed cold spot craters, self-secondaries formed at the downrange of the ejecta deposits have the largest spatial density, while those at the uprange have the smallest density. This density pattern holds for all cold spot craters that were formed by non-vertical impacts, but self-secondaries do not exhibit other systematic density variations at different radial distances or at other azimuths with respect to the impactor trajectory. Among known mechanics of ejecting materials to the exterior of impact craters, impact spallation is the most likely scenario to account for the required large ejection velocities and angles to form self-secondaries. The production population of self-secondaries is estimated based on the highly diverse crater size-frequency distributions across the ejecta deposits of cold spot craters. For a better understanding of the impact history on the Moon, a systematic investigation for the effect of self-secondaries on lunar crater chronology is required. |
| first_indexed | 2024-03-10T13:17:03Z |
| format | Article |
| id | doaj.art-0927c8f991774e26bd01fe8541802eb5 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T13:17:03Z |
| publishDate | 2021-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-0927c8f991774e26bd01fe8541802eb52023-11-21T10:17:53ZengMDPI AGRemote Sensing2072-42922021-03-01136108710.3390/rs13061087Self-Secondaries Formed by Cold Spot Craters on the MoonYiren Chang0Zhiyong Xiao1Yang Liu2Jun Cui3State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau 999078, ChinaPlanetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai 519000, ChinaCentre for Excellence in Comparative Planetology, Chinese Academy of Science, Hefei 230026, ChinaPlanetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-Sen University, Zhuhai 519000, ChinaSelf-secondaries are a population of background secondaries, and they have been observed on top of impact melt and ballistically emplaced ejecta deposits on various planetary bodies. Self-secondaries are formed by impacts of sub-vertically launched ejecta, but the launch mechanism is not confirmed. The potential threat of self-secondaries to the theoretical and applicable reliability of crater chronology has been noted, but not constrained. Hitherto discovered self-secondaries were located around complex impact craters, but their potential existence around simple craters has not been discovered. Here we report the first discovery of self-secondaries around lunar cold spot craters, which are an extremely young population of simple craters formed within the past ~1 million years on the Moon. Self-secondaries are widespread on layers of cascading flow-like ejecta deposits around cold spot craters. The spatial density of self-secondaries dwarfs that of potential primary craters. The spatial distribution of self-secondaries is highly heterogeneous across the ejecta deposits. With respect to the impactor trajectory that formed cold spot craters, self-secondaries formed at the downrange of the ejecta deposits have the largest spatial density, while those at the uprange have the smallest density. This density pattern holds for all cold spot craters that were formed by non-vertical impacts, but self-secondaries do not exhibit other systematic density variations at different radial distances or at other azimuths with respect to the impactor trajectory. Among known mechanics of ejecting materials to the exterior of impact craters, impact spallation is the most likely scenario to account for the required large ejection velocities and angles to form self-secondaries. The production population of self-secondaries is estimated based on the highly diverse crater size-frequency distributions across the ejecta deposits of cold spot craters. For a better understanding of the impact history on the Moon, a systematic investigation for the effect of self-secondaries on lunar crater chronology is required.https://www.mdpi.com/2072-4292/13/6/1087self-secondariesimpact crateringshock mechanicscrater chronologyMoonlunar regolith |
| spellingShingle | Yiren Chang Zhiyong Xiao Yang Liu Jun Cui Self-Secondaries Formed by Cold Spot Craters on the Moon Remote Sensing self-secondaries impact cratering shock mechanics crater chronology Moon lunar regolith |
| title | Self-Secondaries Formed by Cold Spot Craters on the Moon |
| title_full | Self-Secondaries Formed by Cold Spot Craters on the Moon |
| title_fullStr | Self-Secondaries Formed by Cold Spot Craters on the Moon |
| title_full_unstemmed | Self-Secondaries Formed by Cold Spot Craters on the Moon |
| title_short | Self-Secondaries Formed by Cold Spot Craters on the Moon |
| title_sort | self secondaries formed by cold spot craters on the moon |
| topic | self-secondaries impact cratering shock mechanics crater chronology Moon lunar regolith |
| url | https://www.mdpi.com/2072-4292/13/6/1087 |
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