In an offhand comment made in Orthodoxy, G.K. Chesterton wrote of the tasks one would expect only an expert to perform, such as “playing the church organ, painting on vellum, discovering the North Pole (that insidious habit)…” Finding the Pole is a habit? Presumably the North Pole could only be discovered once. But in 1908, when Orthodoxy was published, finding the North Pole was the claim of countless adventurers seeking glory, all of them unsuccessful up to then.Chesterton’s phrase came to my mind this month with Nasa’s announcement that they’d discovered water on Mars. Again? That insidious habit! No one seems to have made a firm count, but I suspect Nasa must have announced the discovery of water on Mars at least a dozen times o