Moon's Fossil Bulge Could Finally Explain Earth's Mysterious Origins

Tuesday, 06 February 2018 - 11:14AM
Tuesday, 06 February 2018 - 11:14AM
Moon's Fossil Bulge Could Finally Explain Earth's Mysterious Origins
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Image credit: YouTube

The moon has a fairly pronounced middle-age spread.

As a result of millennia of spinning around, weight has gathered around the lunar body's equator, giving it a portly appearance that, while not noticeable to the naked eye, has resulted in centuries of debate among astronomers.

Originally it was believed that the moon must have, at one point, been spinning a lot faster than it does now and that something must have happened to cause it to slow down over time before it cooled and hardened, before ultimately losing its atmosphere.

This has long made sense—we're aware that the rotation of both the moon and the Earth are gradually slowing down, so presumably, the moon must have undergone a more dramatic slow-down at some point in its early life. Thus far, though, we've had nothing but speculation to go on when considering the moon's weird shape.

Now, a team of scientists from the University of Colorado Boulder has found evidence that the so-called "fossil bulge" was actually created very slowly, over hundreds of thousands of years.


The team built a computer model of the lunar surface, factoring in everything that we know about its size, shape, and the fact that it's slowly drifting away from the Earth as we too drift away from the sun.

The conclusion was that the moon's bulge must have formed slowly, and that, in order for this to be the case, the Earth must not have been absorbing as much of the moon's gravitational force.

According to lead scientist Shijie Zhong:

Opening quote
"The Moon's fossil bulge may contain secrets of Earth's early evolution that were not recorded anywhere else. Our model captures two time-dependent processes and this is the first time that anyone has been able to put timescale constraints on early lunar recession."
Closing quote

At present, much of the gravitational pull that the moon exerts on the Earth is swallowed up by the ocean—the water sways back and forth across the body of the water as the moon's gravity dissipates harmlessly.

For the moon to have developed a fossil bulge over millennia while still relatively fresh, the Earth must not have had liquid oceans during its Hadean period, shortly after its creation.

This new claim backs up an existing theory which suggests that when the Earth was new, it was entirely frozen thanks to a smaller, weaker sun that wasn't putting out as much heat. As the sun grew and amped up its radiation, the Earth warmed up, the oceans thawed, waves started churning, and the moon's bulge stopped growing.

This so-called "snowball Earth" theory, if true, tells us a lot about how our solar system first formed, and what our planet was like long before any living creatures had developed on its surface. While this new study isn't incontrovertible proof of the theory that the Earth started off as a snowball, it does lend credence to this idea and may help us to get a better understanding about what both the Earth and the moon were like when they were young.

All of this is possible because the moon has a squat pot-belly.