Joshua Rhoades was standing near an abandoned farmhouse in rural Illinois on a windy night in early March, fiddling with his camera, when he noticed what he called “a faint, eerie, ethereal glow” above him. A pillar of light had illuminated the darkness, stretching from the horizon—a hint of sun, but it was nearly 8 p.m.
There was nothing alarming about the sight, though it was, by one definition, a little alien: The glow was the result of an interplanetary cloud of dust particles reflecting sunlight toward Earth. To Rhoades, a geologist with a photography hobby, the display was an item on his bucket list, best viewed around this time of year in places far from light pollution. For astronomers who study space dust, the phenomenon, known as zodiacal light, is at the center of a startling discovery.
Scientists have long known that a cloud of interplanetary dust is responsible for the glow, and that its particles come from asteroids and comets, which shed dust as they travel into the inner solar system from afar. Researchers have collected some of these particles, sweeping them from Earth’s atmosphere and excavating them from Antarctic snow, and their composition lines up with the known properties of those celestial objects. But new research suggests that some of the dust might be coming from elsewhere in the solar system. Rhoades actually captured the potential source in the photograph he took that night: Mars, a little orb trapped in the column of light.