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Collision With Planet Dwarf Causes Like Our Moon to Be Lopsided



The artist's picture of a massive collision involving two large objects.
Image: NASA / JPL-Caltech

Our Moon includes the nearest and far side with very different geological features. This anomaly has caused confusion for scientists for many years, but new computer simulations suggest that the asymmetrical disposition of the Moon can be traced back to an ancient collision with another object – possibly a small planet.

For thousands and thousands of years, humanity had no idea what the far side of the Moon was. Our natural satellite is locked by the tide to the Earth, forcing us to look permanently at one of its two hemispheres. However, starting with the Apollo missions, however, finally we had the ability to investigate the invisible face of the Moon. Surprising astronomers found two Moon shots showed striking differences in topography, crusty thickness and chemical composition. Scientists counted that this obvious asymmetry was the result of ancient, but unknown, physical processes.

Maps showing differences in moon topography (A), crusty thickness (B), and thorium (C) classification. The star on the top right shows the possible effect on the nearest side.
Image: JGR: Planets / Zhu et al. 2019 / AGU.

New research published in the Journal of Geophysical Research: Planets suggesting that this unexpected asymmetry was caused by an ancient collision with a rather large object, which is likely to be a small planet.

“This is a very thought provoking paper,” said Steve Hauck, a planetary geodynamics professor at Case Western Reserve University who was not involved in the study, in a press release. “Understanding the origin of the differences between the nearest side and the opposite side of the Moon is a fundamental issue in moon science,”
Hauck, chief editor of JGR: Planets added.

The main author of the new study, Zhu Meng-Hua of the Space Science Institute at the Macau University of Science and Technology, had had fun on the side asymmetry close to the side as a result of a celestial collision after looking at data collected in the t 2012 by the Gravity Recovery Mission and Internal Laboratory (GRAIL). This data showed that the distance crust was about 10 kilometers (6 miles) thicker than the crust on the near side. Moreover, the opposite side also showed an extra layer of crust containing materials rich in magnesium and iron.

Using GRAIL data, Zhu ran a series of computer simulations to test the theory that a massive collision left the Moon mixed. In total, 360 different computer models were conducted to determine whether the effect of producing the same type of physical features seen on the Moon today.

Effect has been modeled a 780 kilometer wide object containing a 200-kilometer wide iron core hitting the Moon at 22,500 km / h (14,000 miles per hour). The correct halves represent the temperature variations during the impact process, and the black arrows at (C) and (D) show the movement of debris around the Moon.
Image: JGR: Planets / Zhu et al. 2019 / AGU.

From the simulations carried out, two were compatible with GRAIL data. In particular, the side asymmetry near the pavement has been shown to be caused by a large object measuring 780 kilometers (480 miles) diameter and hitting the Moon side at 22,550 km / h (14,000 mph) or slightly smaller object at 720. kilometers across (450 miles) at a higher speed of 24,500 km / h (15,000 mph). By comparison, the dwarf plant Ceres is 945 km (590 miles) across.

These two scenarios started large amounts of debris and lawn back down to the moon's surface, particularly on the opposite side of the collision. The fallen material buried the primordial crust on the far side with a layer measuring 5 to 10 kilometers (3 to 6 miles) thick, consistent with the observations made by GRAIL. The authors of the new study said that the object is likely to be a small planet in the orbit around the Sun and not in the second moon of Earth.

Importantly, the new study has the potential to solve an ongoing mystery about differences found in isotopes of potassium, phosphorus, and various elements of rare soil between the Earth and the Moon. This new theory explains this inconsistency happily by suggesting that the elements have later arrived to the Moon through the effect.

Excitingly, the new result could also explain similar asymmetrical features found on other planets in the solar system, including Mars.

“In fact, many planets have hemispheric diets, yet for the Moon we have a lot of data to be able to test models and theories with them, so the implications of the work could be wider than just the Moon,” said Hauck.

Our collection is interesting, but one that relies heavily on computing models. Other researchers should run their own simulations, ideally with data collected from GRAIL and other sources. It would be interesting to see, for example, if others can match the fall patterns seen in the new study. Future research should also focus on the presence of “alien” material on the Moon (eg the remnants of the alleged small planet) which could further complement the findings of the newspaper. Until then, the new theory will have to remain the same – theory.


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