The Sun dips to the Martian horizon in a blue-tinged sky in images sent home to Earth last week from Curiosity, NASA said in a statement. The imaging was done between dust storms, but some dust remained suspended high in the atmosphere, Science Daily reported. The sunset observations help researchers assess the vertical distribution of dust in the atmosphere.

"The colours come from the fact that the very fine dust is the right size so that blue light penetrates the atmosphere slightly more efficiently," Mark Lemmon of Texas A&M University, the Curiosity science-team member who planned the observations, said.