Longevity of Signs of Civilization on the Moon

Question

I was just reading this question, which just got me thinking about whether evidence of civilization would last longer on the moon.

Civilization

What sort of civilization am I talking about? I'll list a few specific things, to make the question less open ended, but if you have an idea for something reasonable, go ahead. If you want, focus on a single part of this question.

City Hall

The mayor of a wealthy town on the moon decided to build a city hall completely out of marble. Why would he import marble from earth, and why would he make the whole building out of it? He was rich, and that usually is reason enough. This is a generic American city hall with some columns in the front, complete with offices, bathrooms, and the like. Three years after its construction, the dome around the city starts gradually leaking, and the city hall is left as it was on the monday before the leak, with lunar atmosphere gradually replacing the Terran atmosphere.

Open Pit Mine

A functioning open pit mine nearly identical in layout and size to the Bingham Canyon Mine is likewise abandoned, with work vehicles and heavy equipment stored in nearby hangers. What were they mining? Radioactive Moon dust.

Suburban House

A small ranch style house with a lawn, separate garage, doghouse, white picket fence, and a few sturdy oak trees for good measure. Again, the inhabitants left for work one day and never came back, with the atmosphere slowly becoming lunar.

Details

These structures are located on the dark side of the moon. They were built during the early jurassic period, 201.3 million years ago. We, modern society, are either just discovering them now, or had only just discovered them during the space race.

The house and city hall had been encased in a dome and terran atmosphere during and after construction. However, the dome was breached and slowly leaked terran atmosphere (Earth air gasses, standard Earth air pressure and humidity) until it was entirely lunar atmosphere, at which point the dome disappeared for unknown reasons. The mine was never covered in any way.

What would remain of the structures? What would remain of the interiors and objects in the structures? If there is a specific detail you would like to change in this question in order to answer it in a manner that pleases you, feel free.

Answer 1

As there is no atmosphere on the Moon and no life there will be (almost) no decay at all; the only reasons for decay are:

• an initial evaporation of all volatile substances, this will take very little time once protection from dome is gone.
• thermal cycle: temperature in illuminated zones varies several hundred degrees between "day" and "night" (non-illuminated surfaces won't be affected by this); Some substances are affected by this and will decay in various ways, sometimes breaking down to powder.
• meteoric bombing: having no atmosphere to protect it Moon is subject to meteoric rain damage much more than Earth, but it already cleared its path from most debris (as the many craters testify); eventually any single place will be hit (statistically), but it may take many million years... OTOH you may be unlucky and a big meteor can wipe everything out tomorrow.