Mars is an insistent planet. Many ancient civilizations took it to represent the god of war. Gustav Holst, following their lead, characterized it with swirling currents of discontent and alarming rhythms, threatening to swell out of the orchestra and take over the auditorium. Most of the night sky has been blotted out to the view of city dwellers, but it’s still possible to witness Mars on its wandering course; I’ve seen it often in recent months, glowing red like a warning. It seems to demand t...