التفاصيل البيبلوغرافية
| العنوان: |
The Apollo 17 Regolith: Induced Thermoluminescence Evidence for Formation by a Single Event ∼100 Million Years Ago and Possibly the Presence of Tycho Material. |
| المؤلفون: |
Sehlke, A., Sears, D. W. G. |
| المصدر: |
Journal of Geophysical Research. Planets; Apr2024, Vol. 129 Issue 4, p1-17, 17p |
| مصطلحات موضوعية: |
DRILL cores, THERMOLUMINESCENCE, CORE drilling, PHOSPHATE minerals, THERMOLUMINESCENCE dating, REGOLITH, TRACE elements |
| الشركة/الكيان: |
UNITED States. National Aeronautics & Space Administration |
| مستخلص: |
We explored the geological history of the Taurus‐Littrow Valley at the Apollo 17 landing site through the induced thermoluminescence (TL) properties of regolith samples collected from the foothills of the Northern and Southern Massifs, from near the landing site, and from the deep drill core taken in proximity to the landing site. The samples were recently made available by NASA through the Apollo Next Generation Sample Analysis program in anticipation of the forthcoming Artemis missions. We found that the two samples from the foothills of the massifs exhibit induced TL values approximately four times higher than those of the valley samples. This observation is consistent with their elevated plagioclase content, indicating their predominantly highland material composition. Conversely, the valley samples display induced TL values characteristic of lunar mare material. The samples from the deep drill core demonstrate uniformly induced TL properties, despite originating from depths of up to 3 m. Notably, one of the samples from the lower section of the deep drill core presents anomalous‐induced TL readings. This anomaly coincides with elevated levels of low‐potassium KREEP along with reduced quantities of anorthositic gabbro and orange glass, and could be due to the traces of phosphate minerals. Alternatively, this observation raises the possibility that this sample contains Tycho impact material. The induced TL data is consistent with the regolith, extending to a depth of at least 3 m, having been deposited by a singular event approximately 100 million years ago. This timing aligns with the hypothesized formation of the Tycho crater. Plain Language Summary: We studied the geologic history of the Taurus‐Littrow Valley through the induced thermoluminescence (TL) properties of Apollo 17 regolith samples. Thermoluminescence refers to the light emission of a sample when it is heated. Our investigation focused on samples that were collected from the foothills of the Northern and Southern Massifs, from near the landing site, and from the deep drill core taken in proximity to the landing site. We found that samples from the foothills of the massifs induced TL levels four times higher than those from the valley floor. We attribute this difference to their differing plagioclase content, whereby the TL of foothill samples is comparable to highland material, and valley floor TL is comparable to mare material. The induced TL properties in the deep drill core are mostly uniform. However, one of the samples within the lower section of the deep drill core exhibited anomalous‐induced TL levels. This coincides with elevated levels of low‐potassium KREEP along with reduced quantities of anorthositic gabbro and orange glass, which could be due to traces of phosphate minerals. Alternatively, this sample may contain Tycho impact material. Our TL data suggest that the valley floor regolith was deposited by a single event approximately 100 million years ago, aligning with the hypothesized formation of the Tycho crater. Key Points: The samples from the deep drill core demonstrate uniformly induced TL propertiesThe TL anomaly in the lower section of the deep drill core coincides with elevated KREEP level. Alternatively, anomalies may represent Tycho materialTL data suggest deposition of valley regolith of at least upper 3 m during a single event, potentially 100 Mya during Tycho impact [ABSTRACT FROM AUTHOR] |
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