NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft has returned data that gives scientists new insight into the moon's complex and turbulent history.
Three papers on the data were published in the September 17 issue of Science. One, authored by James Head of Brown University, examined detailed topographical data obtained by the LRO's Lunar Orbiter Laser Altimeter (LOLA), which bounced lasers off the scarred surface of the moon. Head said, according to NASA:
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 [...] The highlands have a greater density of large craters compared to smaller ones, implying that the earlier population of impactors had a proportionally greater number of large fragments than the population that characterized later lunar history.
The Moon's ancient craters have remained relatively untouched, except by other impacts, NASA reports. These craters can provide clues to the history of Earth, where wind, water and tectonic shifts erode or erase impact craters. "The moon is thus analogous to a Rosetta stone for understanding the bombardment history of the Earth," said Head. "Like the Rosetta stone, the lunar record can be used to translate the 'hieroglyphics' of the poorly preserved impact record on Earth."
Head, who identified 5,185 craters on the Moon, believes his findings support the theory that the Moon "was bombarded by two distinct populations of asteroids or comets in its youth," though some of his peers disagree, writes New Scientist.
Scientists have used the LRO data to create what NASA calls "the first-ever comprehensive catalog of large craters on the moon."
The images below are of lunar topographical maps.