Odyssey of Nine — John Russell Fearn

Ward Jackson and his wife make an incredible spaceship journey, exploring every planet in the solar system from Mercury to Pluto, in an attempt to unravel the cosmic mathematical mystery of the number 9 by finding machines and clues buried on each planet by a long-vanished alien race. Jackson believes that the ninth son of a ninth sun should have the inherent gift of leading his race to domination if the continuity was not broken. A rousing interplanetary odyssey based in the odd facts surrounding the number 9 as outlined in the famous Ripley's Omnibus Believe it Or Not.