"You never can tell. Excavation probably won't be much use. These things are on a raised rock foundation, swept clean by the wind. And you can see that the rock itself is native—" he indicated the ledge beneath their feet—"and was cut out a long while back."
"How long?"
Ball toed the sand uncomfortably. "I wouldn't like to say off-hand."
"Make a rough estimate."
Ball looked at the captain, knowing what was in his mind. He smiled wryly and said: "Five thousand years? Ten thousand? I don't know."
Steffens whistled.
Ball pointed again at the wall. "Look at the striations. You can tell from that alone. It would take even a brisk Earth wind at least several thousand years to cut that deep, and the wind here has only a fraction of that force."
The two men stood for a long moment in silence. Man had been in interstellar space for three hundred years and this was the first uncovered evidence of an advanced, space-crossing, alien race. It was an historic moment, but neither of them was thinking about history.
Man had been in space for only three hundred years. Whatever had built these had been in space for thousands of years.
Which ought to give them, thought Steffens uncomfortably, one hell of a good head-start.