obe Mariner 9 went into orbit around Mars, only to be totally by a planet-wide dust storm. This took weeks to settle, during which time it was learned that the surface was much colder than usual - 30° C - and was slowly warmed when the dust settled. Some scientists, particularly planetary scientist Carl Sagan of Cornell University, were so impressed by this story that they looked at Earth with the question - Could it happen here? Extensive studies showed that there are three possibilities on Earth .
             The first, and most relevant, was the threat of global nuclear war. The second, and much more remote, is the possibility of multiple volcanic eruptions. Sometimes, we have periods of intense volcanism, when the continental plates are more than usually mobile, and there is extensive mountain building. Some have thought that this extinguished the dinosaurs, but Dr David Brez Carlisle of Ontario has shown that volcanic dust deposition at that time was extensive - nearly as extensive as during our own million year history! We face many problems, but global volcanic cooling is not one of them.
             The third and most alarming discovery is believed by an increasing number of scientists to have been the true killer of the dinosaurs, and comes straight from astronomy and space science. As we shall see, so does its solution.
             By the year 1800, astronomers had reached an understanding of Newton's new cosmos, and were looking for underlying laws explaining the positions and birth of the planets. The mathematicians Titius and Bode related all the planets then known in a simple formula; using 1 Astronomical Unit AU = 150 million kilometres, or Earth's distance from the Sun, the planets Mercury to Saturn sto
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