So much was dumb about that whole subplot:
- How did McCoy try the entire EM spectrum against the creatures yet somehow miss ultraviolet?
- Why expose Spock to intense UV and not provide any form of eye protection?
- How do both Spock and McCoy forget the Vulcan inner eyelid exists?
- How is UV supposed to penetrate Deneva's ozone layer, let alone get inside buildings?
The easiest way around all that would have been to postulate a fictional type of radiation that kills the parasite without harming the host. It would go through walls and be like kryptonite for the alien. McCoy didn't think of this radiation at first because it doesn't occur in nature. It has to be artificially generated. The show invented delta rays; they could invent this.
If only someone had recently written a post about "Operation - Annihilate!" and perhaps suggested ways to make it seem more plausible.
I quote from post number 128 on page 7 of:
https://www.trekbbs.com/threads/tos-chronology.304218/page-7
"In 1913 it was discovered that the Earth has an atmospheric layer which adsorbs a lot of ultra violent ultraviolet radiation from the sun. The highest intensity ultraviolet rays are adsorbed by nitrogen in the atmosphere. The types of ultraviolet which can penetrate nitrogen gas are UV-A, UV-B, and A UV-C. Most UV-A reaches the surface of Earth, but only a little UV-B, and none of the deadliest UV-C gets through the Ozone layer. At some wavelengths of UV-B there are hundreds of millions of times as many rays from the Sun at the top of the atmosphere than reach the ground."
"At 72 miles above Deneva, the "ultraviolet satellites" are above the height of the ozone layer on Earth. So the "ultraviolet satellites" should produce light in the UV-A spectrum so that most of it will reach the surface of Deneva."
"The ultraviolet and possibly visible light destroys the creatures, freeing the Denevans."
"I wonder how the Denevan who flew his ship into the sun killed the creature.light wouldn't b penetrate the hull of his h ship, and the windows might not be transparent to ultraviolet light."
"Apparently enough of the visible light and ultraviolet light is reflected from various surfaces to reach the creatures hiding the shadows and kill them. And the creatures that were outside during the dark night would be overwhelmed by the sudden burst of bright light."
"But what about the creatures hiding inside.the bodies of humans? Wouldn't they be shielded from the light by the flesh of the humans they inhabit? When I ride in a car and can turn my face toward the sun and close by eyes I see red light through my eyelids, and when the car passes into shade I see blue instead of red. So if the creatures have tendrils in the upper layers of human skin those tendrils will be burned by light penetrating it."
"On May 1, 2020, I found that the flashlight of my phone is bright enough to light up my finger when it is over the light. My finger glows red. Thus some light can penetrate about half an inch or 1.5 centimeters of flesh. 21st century humans usually have bare heads and hands when outdoors, though I tend to cover up more than most, and TOS era people don't usually wear hats and gloves outdoors."
"So humans controlled by the creatures, working outdoors in space ship yards at night when the creatures don't expect any light, would suddenly have their hands and heads flooded with light, killing the tendrils in their heads and hands, which might set off a cascading systems failure leading to death for the rest of the creature. killing the rest of each creature. If most of the creatures on the planet were inside humans working outside at night, most of them might die, and thus the rest of the creatures might die off since they were part of a super creature that might not survive having the majority of its cells die."
"Possibly the creatures were biological weapons designed to be seeded on a planet, drive the inhabitants to insanity and death, and then be killed off by ultraviolet satellites so the planet could be colonized. And possibly some of the creatures got loose and have been infecting planets every since. Note that the times between planetary infections seem to vary widely. After all the natives of a planet died in madness, a few of the creatures may survive infecting wildlife and eventually infect space travelers who visit the planet. And possibly the creatures were programmed to die when they sensed that their hosts were seeing bright light, explaining how the Denevan pilot was freed from his creature inside the protective hull of his spaceship."
"It is uncertain that all of the creatures are dead. Possibly a few creatures survived, infected various Denevan animals, and multiplied enough to form a new super creature, waiting to infect and control another human. So Deneva, along with Ingraham B, Theta Cygni XII, Lavinius V, and Beta Portolan, needs to be watched closely."
And possibly this helps make the destruction of the creatures seem more plausible.
And of course, today, you wouldn't need Kellam de Forest (up until less than a minute ago, I wasn't aware that he's a person, or that he was, at last report, still alive; I'd always assumed the name referred to a think-tank) to tell you that high intensity UV was a bad idea; you pick any random eight-year-old, and he or she would be able to tell you what high intensity UV does to the human body.
Ain't 20:20 hindsight wonderful?
I am not quite certain that knowledge has reached every eight-year-old. Where I live I sometimes see children, including those over eight, outside bare headed, And although it is a beautiful sight to see the highlights in the hair of blonde haired children glittering gold in the sunlight, I don't think that it is worth the increased risk of skin cancer for them later in life.