"How could we tell?" countered Jarvis. "The next expedition to this golf ball ought to carry an archeologist — and a philologist, too, as we found out later. But it's a devil of a job to estimate the age of anything here; things weather so slowly that most of the buildings might have been put up yesterday. No rainfall, no earthquakes, no vegetation is here to spread cracks with its roots — nothing. The only aging factors here are the erosion of the wind — and that's negligible in this atmosphere — and the cracks caused by changing temperature. And one other agent — meteorites. They must crash down occasionally on the city, judging from the thinness of the air, and the fact that we've seen four strike ground right here near the Ares."

"Seven," corrected the captain. "Three dropped while you were gone."

"Well, damage by meteorites must be slow, anyway. Big ones would be as rare here as on earth, because big ones get through in spite of the atmosphere, and those buildings could sustain a lot of little ones. My guess at the city's age — and it may be wrong by a big percentage — would be fifteen thousand years. Even that's thousands of years older than any human civilization; fifteen thousand years ago was the Late Stone Age in the history of mankind.

"So Leroy and I crept up to those tremendous buildings feeling like pygmies, sort of awe-struck, and talking in whispers. I tell you, it was ghostly walking down that dead and deserted street, and every time we passed through a shadow, we shivered, and not just because shadows are cold on Mars. We felt like intruders, as if the great race that had built the place might resent our presence even across a hundred and fifty centuries. The place was as quiet as a grave, but we kept imagining things and peeping down the dark lanes between buildings and looking over our shoulders. Most of the structures were windowless, but when we did see an opening in those vast walls, we couldn't look away, expecting to see some horror peering out of it.