Alien-contact/ancient-astronaut ""infotainment"" from Aldrin, the second man on the moon (Men from Earth, 1989, etc.) and leading novelist Barnes (Mother of Storms, 1994, etc.). By 2006, various space programs proceed in desultory fashion, spurred mostly by private enterprise and the prospect of space tourism. Then a message arrives from Alpha Centauri revealing the presence of alien encyclopedias on the moon and Mars, left by visiting alien Tiberians in 7000 B.C. In an attempt to recover the encyclopedia on the moon, Earth's leading astronaut, Chris Terence, dies, and the encyclopedia is destroyed. So, a multinational effort gears up to reach Mars and recover the information at all costs. Among all that alien advanced technology, investigators discover, is a chronicle describing how the Tiberians--""alien"" mostly in a metaphorical sense--sent forth starships from their doomed homeworld to colonize as many new planets as they could. The first Tiberian expedition, touching down in the Middle East, resulted in a bloodbath and their enslavement by Stone Age humans. Fifty years later, a wiser second expedition rescued the survivors and determined just in time that the Tiberians couldn't survive on Earth permanently due to biochemical incompatibilities; they retreated to the moon and then to Mars, where they died out. Bulging with facts and explanations--most of them, unfortunately, at the expense of plot, character, and narrative momentum. Still, Aldrin brings an unmistakable hands-on realism to the details of space exploration, and Barnes lends his expertise to the overall structure and packaging.