| Summary: | The nature of lunar light plains isn ot yet fully understood. Although there are unambigious signs of an origin related to the ejecta of the major impacts, especially of the Imbrium and Orientale event, crater-frequency distribution measurements show that several light plains are younger than ejecta blankets from the Orientale basin, supposedly the last basin-forming impact on the Moon. In addition, results from multispectral image analysis at least do not exclude the idea of an involvement of volcanic components during the formation of these plains, thus supporting an origin independent from the Orientale and Imbrium event. This may also involve cryptomaria, as probably exposed at the dark-halo crater Gaertner D. Data sets recently gained with modern digital multispectral VIS-NIR imaging systems of areas poorly visible from the Earth in moderate (Galileo E/M-2) and high resolution (Clementine) proved to be useful for investigations of light plains north of Mare Frigoris, where towards the north pole the greatest concentration of light plains can be found. Some of the identified areas have been analyzed with photogeological methods, the result being discussed in the context of their respective geologic setting and its evolution. Crater counts have been performed and used to derive absolute ages, and have been compared with existing data sets and interpretations of light plains abundant in the highland approximately between the Apollo XIV and XVI landing sites. Where possible, multispectral information has been added to shed new light in the formation of light plains: Because of the detection of both highland and mare spectral signatures a a uniform process for the formation of light plains seems unlikely.
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