Artefact Detected On Callisto.

Name the place, and these artefacts take you there, but, perhaps due to a fault, never in your own time. Don't worry, that's no web of window cracks, you're looking down at Valhalla, the largest known multi ringed impact crater in the solar system. But what the Bradbury is that long structure? And how can it have rusted out here? A base we knew nothing about? Lined with some kind of struts, it appears, and it's open , no roof. Those can't be eggs, can they? No. Wait. Is that rust, after all? Surely Wood. No, they aren't eggs. Helmets.