I was with a team exploring a part of the moon with strange selenography.  There was a large area covered with vaguely cylindrical vertical projections.  While most of the team was investigating something else, I discovered that one of these projections was actually some kind of technological artifact, covered by a thick layer of moondust.  The rest of the team joined me and we started an archaeological dig.

At first we thought perhaps it was some kind of alien installation, but then we started finding evidence that it had been inhabited by humans, who apparently had somewhat more advanced technology than our own.  It was clearly at least tens if not hudreds of thousands of years old, so we started to wonder if there had been some ancient human civilization that had developed space flight.  Then we found that they had used modern written English!  Various documents had a seal of a “Heath Republic”.

Eventually we discovered what we initially thought were human remains, then by accident triggered a mechanism that started reviving them from suspended animation.

Once revived, the people were as surprised to see us as we were to see them.  They explained that while they were at the base, there was a major war on Earth, which completely destroyed the cilivization and left the Earth uninhabitable.  The moon base was not yet self-suffiicent.  They tried to quickly improvise means to become self-sufficient, but were not successful, and finally resorted to suspended animation in the hope that someday they might be discovered and revived.

The war as described could not have happened in the past of our earth, because it would have left evidence which we would have long since discovered, and it also would be unlikely that two similar human species would evolve within a few billion years.  The conclusion we reached was that the fearsome energies released in the war had thrown their moon either back in time from our future, or into our universe from a parallel one.

One of the revived people apparently wasn’t happy about this state of affairs, and secretly triggered a mechanism that would result in the deaths of all of us.  We discovered this too late to prevent it from occuring, but most of the people were able to survive by going back into suspended animation.  Because of some quirk of circumstance, a few of us, myself included, were able to survive the (event? attack?) without needing suspended animation, but we were unable to return to Earth, and it would be many years before we could revive the others.