How to get rid of moon stations?

Question

I have a story where a powerful outside force killed (next to) all humans on earth some decades ago.

The way I want to build it is that it required that the human outposts on the moon to die as well. Unfortunately I want to have the reason of the dying be connected to the air on planet earth. (Kind of a reverse War of the Worlds ending.) But the outposts would have air filters and other high tech stuff available that should have prevented that.

The aliens would strongly prefer to never interact with humans at all; they prefer killing from distance (like the air thing where they introduced a created pathogen). It's okay if there are some dozen survivors - just not enough to make humans relevant for a long Long time. Just sending rockets would not do as the stations are hardened against asteroids, etc. (After all, they are permanent outposts, meant to last.)

Answer 1

Since you prefer to them as outposts, I doubt they would be large enough to have a self-sufficient industrial base capable of maintaining their life-support.

So while they'd be able to produce energy, air, water, food, and bulk materials for repairs, they would not be able to produce the spare parts that the machines doing all that will need. Or if they can, not the spare parts the machines for that will require. Eventually the outposts will start failing without you needing to do anything. And in space any failure is a lethal danger.

It is possible to build moon base that has self-sufficient industrial base, but economic reasons make it unlikely unless people expected they might lose access to the resources of Earth. Not likely for bases on the Moon.

Answer 2

So the aliens introduced a pathogen in the Earth atmosphere? That could have been a virus or similar invading the humans, or a fungus etc. which produces toxins.

Say the fungus is deployed in very resilient spores. They'll last centuries if they don't find a good environment, but the toxin only gets lethal in sufficient concentrations. If just a few spores get to the stations, they're doomed. One of the bases thinks they've dodged the bullet. But on the outside of a packet of freeze-dried herbs, there are a few spores. Once the packet goes into the warm and wet kitchen, the spores go active.

Answer 3

The aliens don't have to do a thing. If the Earth's industrial civilization dies, then the outposts on the Moon are essentially helpless. They are cut off from the tools and spare parts they need in order for their systems to continue working and the gradual cascade of system failures will kill them in an matter of years, perhaps a few decades at most.

The people trapped on the outposts might stretch out their existence by trying to bootstrap their own industrial civilization, but lacking the mass of tools and infrastructure surrounding the real thing, they will be able to mostly cobble together simple things like plumbing and basic electrical infrastructure. Electronics, and especially things like modern integrated circuitry will be impossible to replicate, and as circuit boards and microprocessors fail, the devices dependent on them will also fail.

This will be especially tragic since much of the accumulated knowledge that the people on the Moon will be trying to draw on will be stored in electronic format, so accessing help files or watching YouTube videos on how to fix systems will become more and more difficult as time passes. The other issue is there will be a small pool of people, so any accident that kills a person will also remove their accumulated skills and experience from the available pool, making the remainder less robust and able to deal with emergency situations. (As an aside, this is thought to be one of the reasons the Neanderthals died out; their bands were much smaller than those of our Ancestors, so the death of one man or woman would leave them with large skill gaps and make it harder to survive in late Ice Age Europe).

The people on the Moon were obviously selected for their skills, smarts and ability to work under difficult conditions, so they will likely go down fighting their failing systems to the bitter end, or try to return to Earth if they believe the pathogen or whatever killed the Earth has passed as well. You have the basis for a pretty good story right there.

Answer 4

The aliens siphon off some of Earth's atmosphere, accelerate it to near light speed and send it towards the moon bases. Sending viruses or fungus to the moon bases works okay but that's not very spectacular. Let's get some explosions!

Have the aliens build a particle accelerator that siphons air from Earth, coherently accelerates it to $.999999999999\text{c}$ then aims it at the moon bases. They can push several kilograms of matter a minute essentially making a hyper-hyper velocity projectile. This will get them the explosions they're looking for. The humans will die from the explosion or from the destruction of life support facilities in the base. Granted, the power requirements to perform these kinds of accelerations are staggering but it's a bunch of aliens with an axe to grind.

Answer 5

You mentioned that the aliens introduced a virus into earth's atmosphere. If you have regular traffic going to / from your outposts, it's going to be quite likely that someone is going to carry the virus on their ship over to the outposts, causing them to be infected too. This, in theory, could cause the outposts to die off as well.