According to some researchers, the moon may have been captured during a close encounter between young Earth and the Earth binary (a system consisting of the moon and other rocks). new paper Published in Planetary Science Journal.
Darren Williams and Michael Zugger explored the concept of collisionless binary exchange for capturing large satellites (comparable to or larger than the Moon) around Earth-mass objects inside and outside the solar system.
During six missions to the Moon from 1969 to 1972, Apollo astronauts collected more than 360 kg (800 pounds) of lunar rocks and soil.
Chemical and isotopic analysis of the material showed it to be similar to rocks and soils on Earth. It was found to be calcium-rich, basaltic, and dated to about 60 million years after the formation of the solar system.
Using that data, planetary scientists gathered at the Kona conference in Hawaii in 1984 reached a consensus that the moon formed from debris after it collided with a young Earth.
“The Kona conference set the story for 40 years,” said Darren Williams, a professor at Penn State University.
“But questions still remained. For example, a moon formed by a collision of planets, with the debris clumped together in a ring, should orbit above the planet's equator. Earth's moon should orbit above the planet's equator. It's circling around.
“The moon is more in line with the sun than the Earth's equator.”
“In an alternative binary exchange capture theory. Earth's gravity separated the binary star and latched onto one of the objects, the moon, which became a satellite orbiting its current plane.”
“There is evidence that this is happening elsewhere in the solar system.”
“The leading hypothesis in this field is that Triton, the largest of Neptune's moons, was drawn into orbit from the Kuiper belt, where one in 10 is thought to be a binary star. There is.”
“Triton orbits Neptune in a retrograde orbit, moving in the opposite direction of the planet's rotation.”
“Its orbit is also highly tilted, making an angle of 67 degrees from Neptune's equator.”
Professor Williams and Professor Michael Zager of Pennsylvania State University argue that Earth could have captured an even larger satellite than the moon, an object the size of Mercury or Mars, but the resulting orbit would not be stable. It was determined that there was a possibility that the
The problem is that the Moon's “capture” orbit started out as an elongated ellipse, not a circle.
Over time, the shape of the orbit changed under the influence of extreme tides.
“Today Earth's tides are more advanced than the Moon's,” Professor Williams said.
“The high tide accelerates the orbit. It gives it a pulsation and gives it a little bit of a boost. Over time, the moon moves away a little bit.”
When the Moon approaches the Earth, the effect is reversed, as it was immediately after capture.
By calculating tidal changes and the size and shape of the orbit, the researchers determined that the moon's initial elliptical orbit had shrunk over a timescale of several thousand years.
The orbit also became more circular, until the moon's rotation became fixed in its orbit around the Earth, as it is now.
“At that point, the tides likely reversed and the moon began to gradually move away,” Professor Williams said.
“Each year, the Moon moves 3 centimeters away from Earth. At its current distance from Earth – 385,000 km (239,000 miles) – the Moon feels a significant pull from the Sun's gravity.”
“The moon is so far away right now that both the sun and Earth are competing for your attention. They're both being pulled by it.”
Mathematically, the researchers calculated, a satellite captured in a binary exchange could behave similarly to Earth's moon. However, it is not certain whether this is the origin of the moon.
“No one knows how the moon formed,” Professor Williams says.
“For the past 40 years, we've had one possibility as to how it got there.”
“Now we have two. This opens up a treasure trove of new questions and opportunities for further research.”
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Darren M. Williams and Michael E. Zagar. 2024. Formation of large-scale terrestrial satellites through binary exchange acquisition. Planetary Science Journal 5(9):208;doi: 10.3847/PSJ/ad5a9a
Source: www.sci.news
