A new study suggests that the Moon may have been captured from a binary system, rather than forming from debris after a collision on the young Earth. This intriguing possibility challenges the long-held consensus and opens up a new avenue of investigation into the Moon’s origins.
Challenging the Colliding Spheres Idea
The leading notion over the last 40 years for how the Moon formed was that a Mars-size object collided with Earth, and the resulting debris coalesced into the Moon. But the new work, led by Penn State scientists Darren Williams and Michael Zugger, paints a different picture: That one possibly scenario is that our moon was captured during a near-pass between an early Earth and terrestrial binary system.
But the researchers also note that the moons created from a planetary collision – as many believe our Moon was born from – would have been above the equator of its planet, and whereas Earth’s does not line up with the one over land, it instead lines up more similarly to a plane in line with Sun than it does any plane over Earth. The discrepancy has perplexed scientists for decades, and Yin and egos introduction that the binary-exchange capture theory seems to be a valid one.
Clues from the Solar System
The team relates their findings to other solar system objects that lend credence to the binary-exchange capture theory. They point to the example of Triton, Neptune’s largest moon, which likely was captured into orbit from the Kuiper Belt — a region where many objects are expected to be binaries. The comet that was the source of early Earth’s water most likely also knowcked the Moon into its current tilt, and Triton’s orbit is retrograde with a large angle to Neptune’s equator.
They also found that Earth could have captured a much larger satellite, like the size of Mercury or Mars, but the latter orbit might not be very stable. According to the researchers, the moon was in a relatively elliptical orbit originally, but it gradually converted into an almost circular orbit over thousands of years with the help of its spiral patterns and as lunar spin naturally locked during its attempt to maintain an appropriate distance from Earth.
Conclusion
With this new research, the long-standing theory of how the Moon was formed is being called into question and a different view on its origins has been opened up. Pondering the apparent binary-exchange capture, the research challenges collision theory in a novel and far-reaching manner that will provoke a litany of probing new questions. But as the researchers suggest, there is ‘no one knows how the moon was formed,’ and this study opens up a new and tantalizing pathway in investigating the mysteries of its past.
