July 14, 2009

Spirit creates a dust devil portrait

U.S. scientists say they have combined three images taken seconds apart on Mars using various colored filters to create a portrait of a moving dust devil.

The panoramic camera on NASA's Mars Exploration Rover Spirit was taking exposures through different filters during the 1,919th Martian day of Spirit's mission (May 27) as part of constructing a large color panorama, scientists at NASA's Jet Propulsion Laboratory said. Three westward shots, with several seconds intervening between them, caught a whirlwind in motion. A composite image combining the three exposures to make a color image of the Martian ground shows the dust devil in different colors, according to where it was on the horizon when each exposure was taken.

Dust devils occur on both Mars and Earth when solar energy heats the surface, resulting in a layer of warm air just above the surface, scientists said. Since the warmed air is less dense than the cooler atmosphere above it, it rises, making a swirling thermal plume that picks up dust from the surface and carries it into the atmosphere. This plume of dust moves with the local wind.

More than 650 dust devils have been recorded by Spirit since its operations began in 2004.

The images and more information are available at http://www.nasa.gov/mission_pages/mer/images/merB20090714.html.