Updated March 10, 2020, 2:49 p.m.
The moon has always fascinated people. However, it has not yet been possible to clarify exactly how the Earth’s satellite was created. New data support one of the most common theories.
The isotopic composition of the rocks of the moon and earth may differ more than previously thought. Researchers led by Erick Cano from the University of New Mexico in Albuquerque (New Mexico, USA) measured the isotopes oxygen-17 and oxygen-18 in moon and earth rock with high resolution.
The data support the most common theory of the formation of the earth’s moon, according to which the moon was created as a result of a celestial body colliding with the early earth. The study is in the journal “Nature Geoscience” published.
The moon is special in the solar system. It is very large compared to its mother planet Earth, has a vanishingly small metal core and is very poor in volatile elements.
The following theory was developed in the 1970s: In the early days of the solar system, an approximately Mars-sized celestial body collided with the young earth. Hot rock was thrown into space, from which the moon then formed. The struck proto-planet is called “Theia”, after the mother of the moon goddess Selene in the Greek saga.
Individual rocks of the moon differ in their composition from each other
Samples of lunar rock from the American Apollo missions showed that the surface rocks of the moon have a very similar oxygen isotope composition to that of the earth. This would mean that the forerunners of the moon and earth had an identical isotope composition – which is unlikely – or that the oxygen isotopes of both celestial bodies were mixed intensively after the collision. The latter scenario could not be reproduced in modeling.
According to the new measurements by Cano and colleagues, individual rocks from the moon are now recognizably different in their share of the stable isotopes oxygen-17 and -18. In addition, the variations in oxygen 17 values for moon rock are about three times greater than for earth rock.
The researchers explain this as follows: After the impact, the proto-moon was surrounded by silicate vapor. The vapor immediately after impact hit the moon’s magma ocean well before gravitational stratification occurred.
The steam, which only connected to the magma ocean after stratification, was no longer mixed well and this diversity has been preserved to this day.
Expert expects other results from further analysis
The researchers found the highest levels of oxygen-17 in green, glass-like rock, which presumably comes from deep layers of the moon. They therefore suspect that the deep rock of the moon has an isotope value that is closer to that of Theia. According to the value found for Theia, the proto-planet could have been further away from the sun than the earth
Andreas Pack from the University of Göttingen has also been dealing with this topic for many years. He welcomes the fact that the study brings new aspects to the research. However, the measured data sometimes differed significantly from the values in previous studies.
“These measurements are very, very difficult,” emphasizes Pack. He therefore does not want to rule out the possibility that further analyzes will lead to different results. However, the Göttingen professor is confident that moon rock samples from current and future lunar missions can provide answers to these questions. (dpa / dh)
The United States wants to go back to the moon – NASA has announced that. The plans include a settlement on the moon and these could be implemented as early as 2028.
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