American astrophysicists, analyzing samples of lunar rocks, which have been obtained expedition "Apollo 16," found small fragments of ancient meteorites that fell to the moon for about 3.8 billion years ago, as reported by the publication Science.
A team of researchers led by Katherine Joy of the Lunar and Planetary Institute in Houston, Texas (USA) conducted an analysis of regolith fragments of lunar soil, which was delivered at the 1972 Earth Expedition "Apollo 16." Regolith samples were taken from a giant crater formed as a result of the fall of an asteroid about 3.85 or 3.92 billion years ago, which was named by scientists Mare Imbrium.
They Joy and his colleagues have found microscopic beads - hondruly characteristic only for the primitive chondrites - asteroids saturated with silicon, which appeared due to the primary matter the solar system. The set of these large asteroids collided with the Earth, the Moon and a number of other planets in the heavy bombing that occurred in the earliest stages of the solar system.
The presence of chemicals in the beads was determined by researchers with the electron microscope and a spectrograph to determine the time of their formation and the source of origin.
In most of the samples, as the analysis was quite low iron content, it is not typical of the lunar soil. As part of microscopic beads were also very little nickel and much magnesium as compared with typical terrestrial rocks, which in turn eliminates the possibility of any contamination of the samples provoked by improper storage or careless transportation of regolith.
The results of the analysis of the chemical composition of balls allowed the researchers say that they were born in the ordinary and carbonaceous chondrites, which are in the solar system in the era of late bombardment. Meanwhile, in other samples of lunar rocks have been found traces of more recent clashes that occurred 1.7 billion years ago and later.