With the glow of Earth well-hidden, any dust in the moon’s scant atmosphere around the time of orbital sunrise should become visible. Scientists also expected to see the softly luminous glow of the zodiacal light, an extensive cloud of comet and asteroid dust concentrated in the flat plane of the solar system. The zodiacal light gets its name from the zodiac, that familiar band of constellations the planets pass through as they orbit the sun. Back on Earth, the zodiacal light looks like a big thumb of light standing up from the western horizon a couple hours after sunset in...