|Figure 1||Figure 2|
Wheel tracks left by the NASA rover Spirit's 3-kilometer (2-mile) trek from its landing site to the "Columbia Hills" are visible in this orbital view from the Mars Orbiter Camera on NASA's Mars Global Surveyor. Spirit's rover track shows up nicely from orbit because the surfaces disrupted and churned by the wheels are darker than the surrounding, dust-coated plain. North is up.
The largest crater in the view, dubbed "Bonneville Crater," is about 210 meters (230 yards) in diameter. The picture is a composite of Mars Orbiter Camera image R15-02643, taken on March 30, 2004, when Spirit was near the south rim of Bonneville Crater, and image R20-01024, taken Aug. 18, 2004, when Spirit was climbing the hills' western spur, seen in the picture's bottom right corner.
New Dark Streak Near Spirit
In figure 1, frames taken from orbit 20 weeks apart (top pair) and by the NASA rover Spirit at ground level (bottom) show the formation of a new dark streak on the ground in the area where Spirit was driving inside Mars' Gusev Crater in April 2004. The new dark streak and other dark streaks in the area are believed to result from dust devils removing brighter dust from the surface.
The upper frames were taken by the Mars Orbiter Camera aboard NASA's Mars Global Surveyor. They are from the same pair of images combined to create the orbital view of the NASA rover Spirit's trail from the rover's landing site to the "Columbia Hills." The orbiter took the upper-left picture on March 30, 2004 (Spirit's 85th martian day, or sol). It took the upper-right picture on Aug. 18, 2004 (Spirit's sol 223). A dark streak occurs in the larger crater in the lower right quarter of the August image. This streak was not present when the March image was obtained. Inspection of the lower image, which was taken by Spirit's navigation camera when the rover was at the rim of this crater on sol 106 (April 20, 2004), reveals that the streak was present by then. Thus, the dust devil must have occurred some time between March 30 and April 20. The dust devil was not observed by the rover.
In addition to the formation of this dark streak, another change seems to have occurred at the landing site. The rover track between the lander and Bonneville Crater seems to have faded between March 30 and Aug. 18. This could be an artifact of the different sunlight illumination conditions between the two images, or it may indicate that fine dust settled on the older portions of the track, obscuring it. The Mars Orbiter Camera team plans to re-visit the Spirit lander site from time to time to see what other changes may occur.
Orbital View of Spirit's Neighborhood
The three-frame set in figure 2 is a segmented version of the orbital view of the NASA rover Spirit's trail from the rover's landing site to the "Columbia Hills." The images were taken by the Mars Orbiter Camera on NASA's Mars Global Surveyor. North is up.
The location of Spirit's lander, parachute, and backshell are indicated in frame A, and the rover track down toward the Columbia Hills can be traced through A, B, and C. In frame A, "Bonneville Crater" is the largest crater. Spirit drove up to Bonneville's rim and looked inside before driving away toward the southeast. The base of the Columbia Hills is seen in the lower right quarter of frame C. In frame B, notice that the rover track followed along the edge of a lighter-toned streak and wider dark streak, believed to have been formed by a dust devil before Spirit landed. The proximity of the rover to this streak was not recognized in rover images.