A new look at Mars' eerie, ultraviolet nighttime glow
Every night on Mars, when the sun sets and temperatures fall to minus 80 degrees Fahrenheit and below, an eerie phenomenon spreads across much of the planet's sky: a soft glow created by chemical reactions occurring tens of miles above the surface. An astronaut standing on Mars couldn't see this "nightglow" - it shows up only as ultraviolet light. But it may one day help scientists to bett