Sixty thousand years ago, the Neanderthal people and early modern humans must surely have watched a faint but familiar point of light in the southeastern sky grow brighter and brighter until its brilliant topaz-yellow light outshone everything in the nighttime heavens save the moon. We will never know what those people may have thought or feared, because they left no record among their rare artifacts. But today we do know what they were seeing: It was the distant planet Mars, flying on its elliptical track around the sun and closing its gap on Earth’s orbit while it appeared to blaze in brightness as the two planets neared.