Scientists make a career out of guessing about things that they can’t explain, and some favorite questions to ask focus on Earth’s and our moon’s origin. Traditionally, it has been believed that the moon was formed as a result of a collision which broke a chunk off of Earth, but now a team of scientists have a slightly different theory as to how the moon was formed.
Harvard graduate student Simon Lock led a team of researchers from multiple universities who published a study today on the moon’s origin in the Journal of Geophysical Research: Planets. They hypothesize that the moon was formed out of an enormous “donut-shaped cloud” of vaporized rock, as they describe it, although the technical term for such a cloud is a synestia.
In a press release revealing the results of their study, the researchers explain the traditional theory for the moon’s origin, which is that a heavenly body that was about the size of Mars smashed into the chunk of rock that eventually became Earth. The traditional theory holds that the collision broke that proto-Earth into two chunks of rock, with the larger one becoming Earth and the smaller one becoming the moon.
However, Lock and his team challenge this traditional theory for how the moon was formed. They say that it’s “actually very difficult” for enough mass to end up orbiting Earth the way the moon does now under the traditional scenario. Apparently, the odds of things turning out exactly the way they are today are astronomical, with “only a couple of degree window of impact angles and a very narrow range of sizes,” they explain in the press release.
“And even then, some impacts still don’t work,” they added.
The team of researchers then began to consider other possibilities for the moon’s origin and came up with a theory they believe explains some of the moon’s features that they don’t think fit with the traditional explanation for how the moon was formed. They claim that their model is the first one that’s able to “match the pattern of the Moon’s composition.”
The researchers did say that tests indicate that the “isotopic ‘fingerprint'” of Earth and its moon are almost the same, which probably means their origins are the same. However, they add that under the traditional theory of its origin, the moon was formed largely from what’s left of only one of the two massive chunks of rock that scientists believe smashed into each other eons ago. The problem with this though is that although Earth’s and the moon’s compositions are nearly the same, they’re not an exact match.
Scientists have learned over the years that the moon contains much smaller amounts of certain volatile elements like copper, potassium and sodium, all of which are pretty common on Earth. Lock and his team questioned why there would be such a difference in composition if Earth and the moon’s origin were one and the same, and then they came up with a new theory for how the moon was formed.
They hypothesize that when the massive collision occurred, the huge chunk that eventually became the moon was not a disc as originally suggested. Instead, they believe it was a synestia, which is essentially a huge donate-shaped cloud of vaporized rock. Their new theory suggests that the moon was formed by a little bit of liquid rock that collected next to the synestia, and then it begins raining vaporized rock, some of which flows to the moon, enlarging it.
“The rate of rain fall is about ten times that of a hurricane on Earth,” Lock explained. “Over time, the whole structure shrinks, and the Moon emerges from the vapor. Eventually, the whole synestia condenses and what’s left is a ball of spinning liquid rock that eventually forms the Earth as we know it today.”
