Our moon may have been stolen

According to RCO News Agency, The question of the origin of our unusual moon remains an unanswered question. Currently, the main theory is that the Moon is either a child of the Earth or its sibling, born of the same material in the same region of the solar system.

New research challenges this notion, suggesting that the moon could have been born elsewhere in the solar system and later embraced by Earth’s gravity.

Astronomers Darren Williams and Michael Zugger of Pennsylvania State University have performed calculations and found that gravitational capture of moons is possible for rocky planets like Earth, and thus the likely origin of our present-day Earth-Moon system.

We have a lot of evidence that the Earth and its moons are made of the same material. The mineral composition of both is the same as would be expected if they were composed of the same substance.

The formidable collision hypothesis is a dominant explanation for this similarity. In this way, a large mass has hit the earth and the resulting remains have turned into a planet and a moon.

There are other ways that these two bodies can be made up of the same composition. They may have formed in the cloud of an evaporated planet known as synestia, or perhaps at the same time from the same dust cloud that orbits the Sun.

But as we’ve seen elsewhere in the solar system, there’s more than one way to get a moon. If two masses pass by each other at the right angle and speed, they can be gravitationally connected to each other and eventually enter a stable and long-term orbit.

A specific scenario that might involve the Earth and the Moon is known as a “double capture”. In this scenario, two masses that are already gravitationally bound together pass through a third mass. This third mass traps one member of the binary pair and separates them, leaving one of the two masses for itself.

We know that there are many binary objects in the solar system. For example, we continue to find binary and even triple asteroids. There is even evidence that this three-mass gravitational interaction has created a binary attraction with the Neptunian moon Triton. Triton orbits Neptune in the opposite direction to the rest of Neptune’s moons and at a different angle, which indicates that it has exited the Kuiper Belt and entered Neptune’s orbit.

Williams and Zoger say the moon has an orbit around Earth that is not aligned with the equator, as expected from the origin of the debris cloud. So they did a set of mathematical modeling to determine whether something the size of the Moon could be captured by something the size of the Earth.

According to their calculations, Earth could have captured something even larger (a body the size of Mercury or even Mars), although their orbits would not have been fixed. But something the size of the Moon could have settled into an elliptical orbit that became more circular over time and eventually started moving away at the same rate as the Moon is now receding from Earth, about 3.8 centimeters per year.

So this hypothesis is possible, but there are still other features, such as mineral and isotopic similarities, that are more consistent with a closer relationship between the two bodies than the recording scenario suggests.

This scenario gives us an avenue for exploration and study that can help us not only learn more about our own planet, but also help us understand how such systems form around other stars and elsewhere.

Since the Moon is thought to have played an important role in the evolution of life on Earth, this research could help us find habitable worlds elsewhere in the Milky Way.

“No one knows how the moon was formed,” says Williams. We’ve had one explanation for it for the past four decades, and now we have two. This new scenario opens up a wealth of new questions and opportunities for further study.

This research was published in the journal The Planetary Science.

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