posted 08-09-2014 08:19 AM            

This is the question Stu and I had asked ourselves: if alien spacefarers had visited the Moon some time in the past, and wanted to make contact when the primitive life on Earth had evolved into something interesting, where might they have left some indication of their presence for us to find?

Of course we did not believe in the alien monolith in the 1968 Clarke/Kubrick movie 2001: A Space Odyssey, but alien artifacts on the Moon were not (and are not) totally impossible.

The answer to the question seemed obvious: Mare Orientale, which is a vast multi-ringed crater centered at 17.5 degrees S, 81.6 degrees W, stretching across the western limb. The outer ring of mountains, called Montes Cordillera, is 930 km in diameter. The tallest peaks are 30,000 feet above the central basin, higher than Mt Everest is above sealevel. There is nothing remotely like it anywhere else on the Moon.