I agree that it is a stretch to think that the moon’s disappearance would cause all life on earth to end. Certainly reduced currents would make our weather very different – potentially to the point of a snowball earth scenario. And reduced currents could certainly cause large stretches of ocean to become uninhabitable simply because the winning combo of light from the sun + nutrients for growth would be much rarer. In the open ocean, the nutrients would all settle too far down, below the sunlit levels where photosynthesis takes place.
But the life around geothermal vents probably wouldn’t even notice that anything had changed.
It’s Quora. As it’s open-source, it’s not the most reliable (obviously) but it did raise an interesting thought. I thought I’d post the question here as a stand alone. It was stated without any additional evidence or reasoning.
My goal is not to refute the other source but to get the straight dope from the teeming masses.
However, depending on where life originated, it might be that tidal forces are required for abiogenesis - at least in the way it went down on Earth.
If that is the case, note that there is a place that experiences much stronger tidal forces than a planet with a large moon: the rocky or icy moon of a gas giant. In fact, gas giants cause their moons to experience so much tidal pull that the resulting heat can ensure they can have liquid water even outside what we consider the “habitable” zone, including here in our solar system.
First off, the Moon is not going to “eventually float away.” The reason the Moon is getting further away right now is because the Earth is rotating faster than the Moon orbits the Earth (1 day vs. 27 days). As the Moon gets farther away, though, it slows the Earth’s rotation. Eventually, the whole system will synchronize at 47 days.
With that said, some calculations predict that this tidal locking will take 50 billion years to stabilize. Long before that, the Sun will have expanded into its red giant phase, likely swallowing the Earth and Moon. And long before that, the expansion of the Sun will have evaporated or boiled off the Earth’s oceans, eliminating much of the tidal drag.
I’ve seen it theorized that the Moon and tides might have contributed to the rise of life on land, but see no reason why it would have had any effect on the start of life in the sea.
I also don’t see why the cessation of tides would lead to the extinction of life on Earth. Nor do the tides or the lack thereof necessarily mean the end of ocean currents. Temperature differences are more important, I believe.
Of greater concern is the cessation of plate tectonics, the subsequent erosion of the continents, and the end of the carbon cycle. Oh, and not to mention the aforesaid evaporation of the Earth’s oceans.
The origin of this idea is that there are two ways we know of in which the Earth is unusual: We have life, and we have a very large moon (not the largest in the Solar System, but up there, and far larger than the only other two moons we know of with a rocky-planet primary). Now, granted, we don’t actually know just how unusual either of those traits is: We haven’t even ruled out life elsewhere in our Solar System, and our current techniques wouldn’t really have any hope of finding exo-moons even if they’re very common. But the coincidence of having two ways in which we’re special has led some to wonder, reasonably, if it might not actually be a coincidence.
I had heard this too, and suggested it to my wife when she was working on a lesson about moons for her middle school science class, but she said that didn’t sound right since the moon is so much smaller than the earth and isn’t likely to actually catch many asteroids. So we looked it up and she was right, most asteroids and comets that approach the earth moon pair are a lot more likely to hit Earth than the Moon just because it has a much lower gravity well.
The discussion so far is missing the key role that the moon has played in stabilizing the Earth’s axial tilt. Without that, seasonal variations would be in constant long-term flux, with dire consequences for fostering the evolution of complex multicellular life.
Good point. I just reopened this thread to add that point, but you expressed it more eloquently than I would have.
One caveat I will add is that I’m not sure how much of this is well-established and how much is just a hypothesis, from the magnitude of the effect of the Moon on Earth’s axial stability to how critical this was to the development of complex life.
There’s a guy on YouTube, Artifexian, who does a lot of stuff with regard to building realistic worlds to help people create them to use in fiction, and I’ve actually recently watched most of what he has on the necessary astronomy. He stated in his terrestrial moon video that it was effectively impossible for a terrestrial planet to have a major moon (one in hydrostatic equilibrium) form in place, but it was also absolutely necessary for life to arise on the planet. He basically suggested that every planet that goes on to have life evolve must have the same sort of early collision that would lead to a moon forming as is assumed that produced Earth’s Moon. His reason for requiring the moon was almost entirely “stabilizes the axial tilt”. I’m not sure how it happens, but apparently that stability is what’s needed in order to keep seasonal changes within the same range every year.
He mentioned tides in another video where he noted that a large intertidal zone was most likely necessary in order for life to move out of the water, as there needed to be a way for a sea creature to easily get back in the water after sallying forth onto land briefly in a way that increases fitness for those adaptable to land conditions. It’s incredibly easier if the water just comes back to them compared to having to use limbs adapted for mostly water use to move across land not in an intertidal zone. Thus a larger intertidal zone from larger tides due to a massive moon would be more conducive to land animals evolving.
There was no mention of tidal pools being particularly useful in incubating life, the theory of which shows up in Rush’s Natural Science on their Permanent Waves album, so must be at least 40 years old, and presumably it was not a completely new theory when Neal Peart heard of it… A lot of Artifexian’s astronomy is newer than what I learned in my intro college course in 2000 or so, although evolutionary theory is a rather different subject compared to the changes that have happened in astronomy the last 20-30 years (assuming the newest stuff had yet to filter down to undergrad texts). The way it’s talked about in Natural Science, tidal pools give an increase in the number of different environments available for life to evolve in, and thus lead to higher biodiversity and as such can speed up the development of higher life, but in my mind I have a feeling that it pretty much already requires a largest leaps to have taken place: the formation of the first cell capable of reproducing itself, and the endosymbiosis of mitochondria and other organelles into eukaryotic cells. Without at least rudimentary eukaryotes, I’m not sure if tidal pools make much of a difference, but I’m no expert on this and am just guessing, as I’ve not heard anything remotely scientific with regard to this theory, only random chatter and a 9 minute rock song.
I’ve read Artifexian’s articles too, and even spoken to him online. His ideas are very detailed and comprehensive, and if an earthlike planet without a moon can develop life, that life would be very different to life on Earth. I fall into the camp that suspects that life (or life-like processes) can arise on a much wider range of planetary types than just Earth-like worlds, but it will tend to evolve into forms which are very different from those on Earth. We will be looking in vain for worlds that are exact clones of our own,