Crescent Moon with rock size abundance map. At left of the terminator dividing the day and night sides of the Moon is the sunlit portion of a waning crescent Moon. Part of the unlit night side is at right. Plotted on the night side is a rock size abundance map produced from data obtained by a thermal radiometer called Diviner, one of the instruments on the Lunar Reconnaissance Orbiter (LRO). Based on the rate at which rocks break down into lunar soil, the abundance of large rocks gives an indication of the age of craters. The colour-coding ranges from blue (older) through yellow to red (younger). The most prominent craters visible on the map are Aristarchus (centre left near terminator, 164 million years old), Copernicus (centre, 797 million years old) and Tycho (lower right, 85 million years old). This research, published in 2019, showed that asteroid impacts were lower 290 million years ago than previously assumed, on both the Moon and the Earth.