This is really phenomenal, I'm super impressed by the density, clarity and flavor of all the information, y'all have really pulled off something impressive. The cover art and title are sick. It immediately makes me want to pick it up and dive in.  I love the way you set up everything with the story items and timeline. Everything is super useful, looks great and is well thought out.

A few small notes:
1. I was a little confused by the back and forth between using Dr. Rollo and the Scientist. It made it seem like there were two separate people but I think after reading it is just one person?
2. I too have a villain with a syringe and scalpel finger in my adventure!
3. The ancient god tomb story hook isn't doing much for me personally. I know ancient myth is the theme and you did a great job integrating it, but just for my personal taste I would probably flavor it differently if I ran it.  
4. I don't think the items table is worth the space (although I laughed at the descriptions!) but if you did want to keep it I would make it so you can roll for a random item and maybe  swap out some of the weapons with things more directly plot related. Some hastily ripped open radiation sickness patches or keycard with limited security access or something. Alternatively, the radiation sickness table in the Player's Survival guide is pretty puny, I think developing something that is cranking up the pressure as the adventure goes on would be fun. 
5. For the star in the legend it says Tier 1 NPC (1d10) I'm reading that as how many NPCs are there, I might change it from "NPC" to "NPCs" but I'm not sure what the proper way to do that would be. 

Really fantastic stuff!

Art: What can I say? I'm only a few modules in but if this isn't Best in Jam for art it'll be close.

Writing: Conceptually, it's pretty standard fare for Mothership, and there's no story arc to speak of, just one prolonged action sequence. However, full marks because it executes well on what it sets out to do.

Game Design: Seems like a good action scenario and would get full marks for a board game or video game. For a TTRPG it'd be okay for a very combat-oriented group, but the solitary "win" condition and structural design leave little room for other character types or play styles to have their moment.

Theme: It clearly fits, and you did a good job of giving the artifact some myth-type lore. At the same time, there's no real incentive for the players to engage with the theme, as the scenario is just about trying to trigger the SOS signal. So the theme isn't fully integrated in that you could replace the artifact with a canister of radiation-eating zombie virus or something, and nothing would change.

Layout: Full marks. Professional job. Not going to take a star off for this, but maybe the item table isn't the best use of space. Most of the things there are either generic 1D5 improvised weapons or described in the core rulebook. Maybe use the space to go into more detail about the Tomb of the Father of Suns and possible interactions with it, maybe even a secondary wincon?

Utility: Full marks. If this is the type of scenario someone wants to run, very little prep is needed.

Favorability: Although this absolutely nails the execution for what it's trying to do, it's not what I'm looking for out of Mothership. Structurally, this is more of an action movie, whereas good horror depends on pacing and atmosphere. I think the same scenario would excel with a different system more geared toward tactical combat.