NASA Films Dust Devil on Mars

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COPY AND PASTE LINK ABOVE TO SEE MOTION ON MARS

This movie clip shows a dust devil scooting across a plain inside

Gusev Crater on Mars as seen from the NASA rover Spirit's hillside

vantage point during the rover's 459th martian day, or sol (April 18,

2005). The individual images were taken about 20 seconds apart by

Spirit's navigation camera, and the contrast has been enhanced for

anything in the images that changes from frame to frame, that is, for

the dust devil.

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The movie results from a new way of watching for dust devils, which

are whirlwinds that hoist dust from the surface into the air. Spirit

began seeing dust devils in isolated images in March 2005. At first,

the rover team relied on luck. It might catch a dust devil in an

image or it might miss by a few minutes. Using the new detection

strategy, the rover takes a series of 21 images. Spirit sends a few

of them to Earth, as well as little thumbnail images of all of them.

Team members use the 3 big images and all the small images to decide

whether the additional big images have dust devils. For this movie,

they specifically told Spirit to send back frames that they knew had

dust devils.

 

The images were processed in three steps. All images were calibrated

to remove known camera artifacts. The images were then processed to

remove stationary objects. The result is a gray scene showing only

features that change with time. The final step combined the original

image with the image that shows only moving features, showing the

martian scene and the enhanced dust devils.

 

Scientists expected dust devils since before Spirit landed. The

landing area inside Gusev Crater is filled with dark streaks left

behind when dust devils pick dust up from an area. It is also filled

with bright "hollows", which are dust-filled miniature craters. Dust

covers most of the terrain. Winds flow into and out of Gusev crater

every day. The Sun heats the surface so that the surface is warm to

the touch even though the atmosphere at 2 meters (6 feet) above the

surface would be chilly. That temperature contrast causes convection.

Mixing the dust, winds, and convection should trigger dust devils.

 

Scientists will use the images to study several things. Tracking the

dust devils tells which way the wind blows at different times of day.

Statistics on the size of typical dust devils will help with

estimates of how much dust they pump into the atmosphere every day.

By watching individual dust devils change as they go over more-dusty

and less-dusty terrain, researchers can learn about the turbulent

motion near the surface. Ultimately, that motion of wind and dust

near the surface relates these small dust devils with Mars' large

dust storms.

 

Image Credit: NASA/JPL