It's always good to see more sci-fi on the Zone. Hopefully, we can see more of this!

Some feedback:
*Concerning "Footprints" - I'm loving the setup, though it could use some fine-tuning. However, for short stories, generally, you finish the plot within that story; this feels more like a chapter, or introduction. Also, the moon does have caves! The lava tubes are quite massive, and there's serious talk about utilising them for future lunar colonies.
*Concerning "A Sudden Change" - The technical detail is an excellent touch, but you might want to scale it back a bit; those within the fields might appreciate the touch, but overall it brings a pause to the story, while most people do the math. Also, the setup needs more work, while the plot should definitely be expanded on (see the above)
*Concerning "When All You Have Is A Hammer..." - Great idea to take on a retelling of Norse Mythology - it seems like the Greek gods get all the attention in this area. However, the wording strikes me as too purple in prose, and as a result, it's hard to follow at times. I would also recommend expanding the story, if you want to tell the full "saga" of Odin and his mistress.
*Concerning "Alone" - Midway through, I was half-expecting this to be another take on the "Ancient Astronaut" approach, where humanity either came from the stars, or was guided by visitors in the distant past. Seeing one based on visitors from Phaeton is a refreshing change. This story should definitely be expanded on - a concept like this deserves it's own full-length novel. The only complaint I have about the story is the part where they discuss "unbreakable" constants of reality, then proceed to bend them. While the average viewer won't probably notice, the discrepancy does stand out if you know something about physics. Depending on the story's needs, there's nothing wrong with softening the laws of physics, but it's more confusing to set up one set of rules, then allow for another. Other than that, perfect!

Looking forward to the rest of your work!