Ryan North and Carlos Gomez once again delve into the realm of astrophysics in Fantastic Four #25. Marvel’s First Family is transported to an alternate timeline and an Earth that never had a moon. Reed Richards provides an excellent overview of the Giant Impact Hypothesis, a popular hypothesis regarding the formation of the Moon.
There are five main theories about how our moon formed: fission theory, capture theory, condensation theory, planetesimal impact theory, and ring ejection theory (ignoring the misuse of the word theory here). Masu). Fission theory suggests that the moon was formed by a piece of Earth, probably from the Pacific basin, that separated early in the planet’s life due to Earth’s rotational speed. The capture theory posits that Earth’s gravity captures passing asteroids in much the same way that Jupiter acquired its many moons. Condensation theory proposes the idea that the Earth and Moon formed together in the early days of the Solar System.
The currently accepted giant impact hypothesis includes fragments of both the planetesimal impact hypothesis and the ring ejection hypothesis. The idea is that early in the formation of our solar system, a proto-Earth known as Gaia had a neighboring proto-planet known as Theia. Theia was about the same size as Mars, but some say it may have been much larger, forming at a Lagrangian point in L4 or L5 in a similar orbit to Gaia. Gravitational disturbances from Venus or impacts from large asteroids may have altered Theia’s orbit enough to put it on a collision course with Gaia.
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From here, scientists disagree on some important details. It was initially thought that Theia had given Gaia a blow, which led to Earth’s current tilt and rotation, but the similarities in the chemical composition of Earth and the Moon were not explained (many of the same minerals can be found in both)). A 2012 study showed that the similarity in composition between Earth and the Moon is supported by a more direct collision of the two protoplanets.
Another issue is how quickly the moon formed after the collision. Traditional thinking is that the moon took months to years to accrete from debris created by the collision between Gaia and Theia. A new hypothesis published in Astrophysical Journal Letters suggests that the collision resulted in a satellite made up of a mixture of the mantles of both protoplanets, which was captured in Earth’s orbit just hours after the collision. Masu. This hypothesis further claims that as part of Earth’s accretion, secondary satellites composed primarily of Theia’s mantle material were also created and pulled back into Gaia’s mantle.
Possible evidence for this new hypothesis can be found in the Earth’s mantle as two continent-sized anomalies beneath Africa and the Pacific Ocean. These anomalies have lower seismic velocities and higher iron oxide content than the surrounding material, which is very similar to what we analyzed from the Moon. According to simulations, a direct collision between Gaia and Theia would inject mantle material from Theia into Gaia’s core, while material ejected from the two objects would subsequently form the Moon and the subcrustal mass of these two. It has been shown that there is a possibility that
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Although this is the currently accepted hypothesis for the formation of the Moon, there are still questions that cannot be answered by the giant impact hypothesis, and much research needs to be done to fully understand the origin of our only natural satellite. .
AIPT Science is co-hosted by AIPT and New York City Skeptics.
