The author introduces himself as a catastrophist who believes that the Earth has been affected in the past by sudden, short-lived, violent events, which were worldwide in scope. This book is devoted to his theory that the planet Mars entered into hundreds of catastrophic close encounters with Earth. During these encounters Mars ejected vast amounts of vapourised rock into space and a lot of this fell to Earth. It was this debris that produced the sand that formed Earth's deserts.
We are told that about 6,000 or 7,000 years ago the solar system was very different from what it is today. Earth was about 40 per cent smaller and the continents formed a single landmass. There were no oceans, but "there may have been shallow small streams and lakes". Thus prehistoric people did not have to cross oceans to move around our planet. Earth had no moon in those days, and the planets Venus and Mercury did not exist. Mars had abundant life, including humans.
Around 4,000 BC "a giant interloper" entered our solar system and smashed into Jupiter. As it continues, Gilligan's description of the astronomical events which he imagines gets more and more incoherent. We are told that the collision with Jupiter resulted in the birth of Venus. On Mars, the large feature known as the Valles Marineris is the scar caused by the iron core of the planet being sucked out by one of the planetary close encounters and eventually becomig the planet Mercury. Mars, we are told, was the original home of our ancestors, who somehow managed to avoid being exterminated by these violent events and managed to migrate to Earth. Readers will search in vain for any clues as to how they could possibly have managed this.
It was, of course, the vast amount of material drawn from other planets that rained down on Earth which eventually became the sand that formed the Sahara and other deserts. Gilligan has proved, to his own satisfaction, that more conventional geologists and astronomers don't have a clue, and he has the real answers to questions about the history of Earth and the solar system. However, I think that this book will probably be of greater interest to psychologists and sociologists than to experts in the physical sciences. -- John Harney.