Sky Light
Image by NASA/JPL; Texas A&M; Cornell

The glow of Martian twilight can last for up to two hours after sunset, because sunlight continues to be scattered from the day side to the night side of the planet by abundant dust and ice particles high in the atmosphere. Evening sky shots like this one—taken by Spirit on its 464th Martian day—allow scientists to detect ice cloud structures too faint to be seen in the bright light of midday, and help them measure how high the dust extends.