摘要:
   The impact history of the Moon has been a basis for the calibration of the impact history on terrestrial planets. Self-secondaries are formed by the landing of impact fragments that were launched near vertically with respect to the surface tangent during the early stage of impact cratering. Study of self-secondaries is important to improve both the crater chronology system and impact cratering mechanism. We take the "cold spot" crater on the Moon as the entry point, and 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. 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. This work in integrated into the current analyses of the Chang’E-5 samples.