Detection of visible-wavelength aurora on Mars

Mars hosts a variety of auroral processes despite the planet’s tenuous atmosphere and lack of a global magnetic field. All aurora detections reported to date have been observed at ultraviolet wavelengths from orbit. Here we describe the discovery of visible-wavelength aurora at Mars, originating from the green atomic oxygen line at 557.7 nm. We used near-real-time simulations of a Mars-directed coronal mass ejection (CME), which provided sufficient lead-time to schedule a auroral observation with the SuperCam and Mastcam-Z instruments on the Mars 2020 Perseverance rover. The emission was observed three days after the CME eruption, suggesting the aurora was induced by particles accelerated by the moving shock front. This detection represents the first observation of aurora from any planetary surface other than Earth, the first detection of visible-wavelength aurora at Mars, and demonstrates that auroral forecasting at Mars is possible. During events with higher particle precipitation, or under less dusty atmospheric conditions, aurorae will be visible to future astronauts.