MAVEN has discovered bright transient emission from hydrogen in the Mars upper atmosphere. The emission is correlated with abnormally high fluxes of solar wind protons inside the Martian magnetosphere, indicating that a small fraction of incident solar wind protons collide with the Mars extended atmosphere, become neutral hydrogen, and penetrate the magnetosphere to low altitudes. Also, some neutral particles release energy as ultraviolet light.
This represents the first detection of proton-induced aurora at Mars, which are a hallmark of direct energy deposition by the solar wind in the Martian atmosphere.
