NASA's Phoenix Mars Lander has photographed several dust devils dancing across the arctic plain last week and sensed a dip in air pressure as one passed near the lander. These dust-lofting whirlwinds had been expected in the area, but none had been detected in earlier Phoenix images. The Surface Stereo Imager camera on Phoenix took 29 images of the western and southwestern horizon on September 8th, during mid-day hours of the lander's 104th Martian day. The next day, after the images had been transmitted to Earth, the Phoenix science team noticed a dust devil right away. At least six different dust devils appear in the various images captured by the Lander, some of them in more than one image. This photo reveals one in the upper left corner of the photo. The dust devils range in diameter from about 2 meters (7 feet) to about 5 meters (16 feet).