We also know, from studies of characteristics that have been etched into the Earth across geologic history, that early on, our planet revolved considerably more fast about its axis, and — given the principles of angular momentum — that means that the Moon was much closer to Earth in the past. Now, let’s put these three pieces of knowledge together:
Now, imagine it: we have a young, hot Earth that’s in close proximity to a tidally locked huge Moon, which itself originates from a puffy cloud known as a synestia and may build, as part of the aftermath of the collision, a circumplanetary disk of materials around the Earth. As you might assume, this surplus material doesn’t exist forever, but much of it will finish up falling on (and contributing to) the Moon, on both the Earth-facing and the away-from-Earth sides.
What would this indicate, as far as the similarities and differences between the two faces of the Moon, in such a scenario?
The intricacies of this were just figured out, for the first time, 10 years ago, in a paper by Arpita Roy, Jason Wright, and Steinn Sigurdsson. The key realization is that the heat from the young, hot Earth — an extreme version of Earthshine — should have produced not only a temperature gradient affecting the material surrounding the Earth, but also a chemical gradient: where heavier elements that are closer to the hot Earth are more easily vaporized, but those same elements, when farther away, are less easily vaporized.
Elements like calcium and aluminum, in particular, should preferentially be deposited on the lunar far side as compared to the lunar near side, which means we now have a prediction to look for: greater abundances of these easily vaporized elements on the side of the Moon that always faces away from Earth. The authors then went on to show that greater abundances of calcium and aluminum in the more distant part of the Moon-forming structure — either a circumplanetary disk or a synestia (the latter of which wasn’t coined until a couple of years later) — would lead to a thicker crust on the lunar far side as compared to the lunar near side. Because the crust is the least thick region of a globe, virtually “floating” over the internal mantle, it should equate to larger heights on the far side as well.
In other words, if this is the origin narrative for our Earth-Moon system, then there’s now a testable prediction: certain easily-vaporized elements should be more common as part of the lunar far side’s crust as compared to the lunar near side’s crust. If the Moon were constructed so that it was absolutely (or nearly-perfectly) tidally locked to Earth, then the near side should be deficient in these elements, while the far side should be bountiful in them. On the other hand, if the Moon spun regularly during its development, then these elements should be deposited the same way char is put on a rotisserie chicken: pretty uniformly throughout its surface.
This idea, although it garnered relatively little public notice when it was initially offered, should now be of tremendous interest to planetary scientists, as for the very first time in history, mankind now has the materials necessary to put it to the test. On June 25, 2024, the Chang’e-6 mission successfully returned more than two kilos of lunar samples from the Moon’s far side: the first rocks from the far side of the Moon ever to be brought back to Earth. Although the Apollo missions (as well as later flights by the Soviet Union and China) returned many lunar samples earlier, from both the low-lying maria areas as well as from the highly cratered lunar highlands, all had been from the Moon’s near side.
Why is our moon two-faced?
A massive collision billions of years ago near Earth's moon's south pole might explain why the near and far sides are so different. The face that the moon presents to Earth is very different from the one it hides on its far side.
What is the mystery of the Moon?
Scientists believe that the moon developed as a consequence of a collision between Earth and another planet because rock samples gathered during Apollo flights to the moon indicate parallels in Earth's and the moon's chemical makeup and isotopes.
What is the hidden face of the Moon?
The opposite face, most of which is never seen from Earth, is hence referred to as the "far side of the Moon". Libration has caused certain crescent-shaped edges on the far side to appear over time.
Evelyn Harper
We also know, from studies of characteristics that have been etched into the Earth across geologic history, that early on, our planet revolved considerably more fast about its axis, and — given the principles of angular momentum — that means that the Moon was much closer to Earth in the past. Now, let’s put these three pieces of knowledge together:
Now, imagine it: we have a young, hot Earth that’s in close proximity to a tidally locked huge Moon, which itself originates from a puffy cloud known as a synestia and may build, as part of the aftermath of the collision, a circumplanetary disk of materials around the Earth. As you might assume, this surplus material doesn’t exist forever, but much of it will finish up falling on (and contributing to) the Moon, on both the Earth-facing and the away-from-Earth sides.
What would this indicate, as far as the similarities and differences between the two faces of the Moon, in such a scenario?
The intricacies of this were just figured out, for the first time, 10 years ago, in a paper by Arpita Roy, Jason Wright, and Steinn Sigurdsson. The key realization is that the heat from the young, hot Earth — an extreme version of Earthshine — should have produced not only a temperature gradient affecting the material surrounding the Earth, but also a chemical gradient: where heavier elements that are closer to the hot Earth are more easily vaporized, but those same elements, when farther away, are less easily vaporized.
Elements like calcium and aluminum, in particular, should preferentially be deposited on the lunar far side as compared to the lunar near side, which means we now have a prediction to look for: greater abundances of these easily vaporized elements on the side of the Moon that always faces away from Earth. The authors then went on to show that greater abundances of calcium and aluminum in the more distant part of the Moon-forming structure — either a circumplanetary disk or a synestia (the latter of which wasn’t coined until a couple of years later) — would lead to a thicker crust on the lunar far side as compared to the lunar near side. Because the crust is the least thick region of a globe, virtually “floating” over the internal mantle, it should equate to larger heights on the far side as well.
In other words, if this is the origin narrative for our Earth-Moon system, then there’s now a testable prediction: certain easily-vaporized elements should be more common as part of the lunar far side’s crust as compared to the lunar near side’s crust. If the Moon were constructed so that it was absolutely (or nearly-perfectly) tidally locked to Earth, then the near side should be deficient in these elements, while the far side should be bountiful in them. On the other hand, if the Moon spun regularly during its development, then these elements should be deposited the same way char is put on a rotisserie chicken: pretty uniformly throughout its surface.
This idea, although it garnered relatively little public notice when it was initially offered, should now be of tremendous interest to planetary scientists, as for the very first time in history, mankind now has the materials necessary to put it to the test. On June 25, 2024, the Chang’e-6 mission successfully returned more than two kilos of lunar samples from the Moon’s far side: the first rocks from the far side of the Moon ever to be brought back to Earth. Although the Apollo missions (as well as later flights by the Soviet Union and China) returned many lunar samples earlier, from both the low-lying maria areas as well as from the highly cratered lunar highlands, all had been from the Moon’s near side.
Why is our moon two-faced?
A massive collision billions of years ago near Earth's moon's south pole might explain why the near and far sides are so different. The face that the moon presents to Earth is very different from the one it hides on its far side.
What is the mystery of the Moon?
Scientists believe that the moon developed as a consequence of a collision between Earth and another planet because rock samples gathered during Apollo flights to the moon indicate parallels in Earth's and the moon's chemical makeup and isotopes.
What is the hidden face of the Moon?
The opposite face, most of which is never seen from Earth, is hence referred to as the "far side of the Moon". Libration has caused certain crescent-shaped edges on the far side to appear over time.