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.