"jul448 hot" appears to be a compact phrase combining an identifier ("jul448") with the adjective "hot." Interpreting it for an explanatory report, the most likely meanings are:
The engine’s surface was etched with a language Lian had only seen in the ruins of the ancient Terran colonies on Mars. She recognized the glyph for “heat” and for “life.” The alien script seemed to repeat a phrase:
The alien offered them a choice: and report the discovery, sealing the cavern forever, or stay and become the new custodians, learning to harness the heat and awaken the planet’s buried ecosystems.
Quick diagnostic checklist (useful across interpretations)