The Moon has orbited Earth since the Solar System’s early days. Anyone who’s ever spent time at the ocean can’t fail to notice the Moon’s effect. The Moon drives the tides even in the world’s most remote inlets and bays. And tides may be vital to life’s emergence.

But if Earth were more massive, the Moon may never have become what it is now. Instead, it would be much smaller. Tides would be much weaker, and life may not have emerged the way it did.

The widely-believed Giant Impact Hypothesis explains the Moon’s formation. A Mars-sized protoplanet named Theia crashed into the young Earth, sending molten material into space. That material formed a disk around Earth which eventually coalesced into the Moon.

A new study examines the process laid out in the Giant Impact Hypothesis and shows that rocky planets more massive than Earth might not form large life-enabling satellites like Earth’s Moon.

The Moon formed as a result of a collision between the Earth and a protoplanet named Theia, according to the widely-believed Giant Impact Hypothesis. Credit: NASA/GSFC
The Moon formed as a result of a collision between the Earth and a protoplanet named Theia, according to the widely-believed Giant Impact Hypothesis. Credit: NASA/GSFC

The paper is “Large planets may not form fractionally large moons.” The lead author is Miki Nakajima, assistant professor of Earth and Environmental Sciences at the University of Rochester. Nature Communications published the paper.

The Moon is critical to life on Earth. The tides it causes are critical because life may have originated in intertidal zones. Intertidal zones are some of the most biologically diverse and nutrient-rich regions on Earth, partly because tides deliver regular quantities of ocean nutrients to the regions. Four billion years ago, Earth already had oceans, and the Moon may have been half the distance away that it is now. So the tides would have been even more extreme.

Strong tides create an extreme environment, forcing creatures to adapt. This pressure helped drive speciation, which pushes populations to develop into new species. The Moon also acts as a ballast by stabilizing Earth’s spin axis. That stabilization helps moderate Earth’s climate, enabling life to evolve into more and more complex forms. The Moon has undoubtedly shaped the course of life on Earth, of which we are the most complex expression. Thanks, Moon.

We may have Earth itself to thank for having just the right size moon. Our Moon is relatively large compared to Earth, and in the context of other planet-moon relationships in the Solar System. The other planets in the Solar System have much smaller moons relative to their masses. According to the authors of this new paper, only certain types of planets—and specific sizes—can form moons the size of Earth’s moon. And that has clear implications for the emergence of life elsewhere in the Universe, just as it has on Earth.

“By understanding moon formations, we have a better constraint on what to look for when searching for Earth-like planets.”

Miki Nakajima, lead author, University of Rochester.

“By understanding moon formations, we have a better constraint on what to look for when searching for Earth-like planets,” lead author Nakajima said in a press release. “We expect that exomoons [moons orbiting planets outside our solar system] should be everywhere, but so far, we haven’t confirmed any. Our constraints will be helpful for future observations.”

Earth’s Moon is large, but it’s not the largest. There are four moons in the Solar System larger than our Moon. But they orbit Jupiter and Saturn, which are far more massive than Earth. So the Earth-Moon relationship is unique because the Moon is fractionally large. Why is the Moon fractionally large?

The impact between Earth and Theia generated a rotating disk of material around Earth. Much of it eventually coalesced into the Moon, but some material fell back to Earth. If Earth had been more massive, the Moon might look very different or may never have formed at all. Much of this has to do with the vapour content of the disk of material.

The disk of debris created by an enormous impact is different depending on the nature of the planet. Different planets with different masses and compositions produce disks with varying amounts of vapour. And the vapour content can have a powerful effect on the fate of the debris disk.

If there’s more vapour, there’s more drag in the disk. As tiny moonlets began to
Did you miss our previous article…
https://www.mansbrand.com/the-best-plan-for-hiking-the-tour-du-mont-blanc/

Comments

0 comments