Putting together the Moon’s “detailed global topographic map” captured by the Lunar Reconnaissance Orbiter (LRO), NASA has come to the conclusion that the satellite had a “turbulent youth” – a period when it was battered by “two distinct populations of asteroids or comets.”
An analysis of the images captured by LRO’s Lunar Orbiter Laser Altimeter (LOLA) indicates that the Moon’s surface underwent an early large-fragment bombardment, after which relatively small objects assailed the satellite.
Noting that the analysis includes the Moon’s view “from the vantage point of the eastern limb,” James Head of Brown University said in that most recent edition of Science: “Our new LRO LOLA dataset shows that the older highland impactor population can be clearly distinguished from the younger population in the lunar 'maria' - giant impact basins filled with solidified lava flows.”
Head further elaborated that since the highlands have a comparatively greater density of large craters vis-à-vis the smaller ones, it is apparent that the initial population of impactors probably had a much greater number of large fragments in proportion to the population that characterized the Moon’s history later on.
Noting that crater-gazing may play a significant role in studies about the Earth having suffered at the hands of comets and asteroids, the analysis unfolds evidence of the pounding of the lunar surface, including the “110-mile-diameter, partially buried crater at Chicxulub, in the Yucatan Peninsula of Mexico”, which was a consequence of a significant thump 65 million years back!