"It's pretty cool," said Jim Bell, a Cornell University astronomer and lead scientist for the panoramic camera, or Pancam that took the images.

A series of three pictures was made at about 5:30 p.m. Mars time as the Sun headed toward the horizon near the equator at Meridiani Planum. The sky, Bell said, is about twice as dusty as what was photographed at the Mars Pathfinder landing site in 1997.

"As the Sun sets it dims substantially," Bell said. "Those of you who live in Los Angeles will be very familiar with this effect."

Bell unveiled the images at a press conference at NASA's Jet Propulsion Laboratory in Pasadena.

The sky color is about what an astronaut would realistically see from the surface. A blue halo surrounds the Sun, because dust scatters blue light from the Sun in a forward direction more efficiently than red light, Bell said.

More sunset images will be produced and compared with similar photographs made by the Viking and Pathfinder landers, so researches can learn more about variations in atmospheric dust with the seasons.

• Mars Rovers: Full Coverage