The 2001 Great Dust Storms 8
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The 2001 Great Dust Storms 8

October 20, 2009
One interesting observation by the camera did not involve taking a picture. The temperature of the front end of the tube that holds and protects the telescope mirror of the high resolution camera is very sensitive to the heat emitted by Mars. That temperature oscillates every orbit, and the average closely follows the annual temperature change as Mars orbits the sun. As soon as the global dust event began, the MOC temperature began to drop (see figure, below). The daily average temperature cooled about 1°C, the daytime average dropped almost 3°, and the nighttime average actually increased by 2/3°. These changes are consistent with models and theories of the influence of dust mixed throughout the atmosphere: high altitude dust reflects sunlight so that less solar energy gets down to the ground to heat it. This cools the planet during the day. Dust throughout the atmosphere also absorbs heat radiated from the surface during the day. At night, this dust is warm and radiates, increasing the heat seen from the planet. In the figure, the measurements shown in blue are those made during the global dust event of 2001 and the measurements shown in red were made exactly one Mars year earlier (when no global dust event occurred). The graph shows a close correlation with the beginning of the storm and, although the dust veil obscured the surface, the temperatures also suggest that the storm's primary climatological impact was over by mid-August, although it will take more than two more months for the atmosphere to clear. Interestingly, the effect on the climate of Mars of the global dust events of 2001 is roughly comparable to but demonstrably less than (somewhat greater in temperature, substantially shorter in duration) the effect on Earth's climate of the dust and aerosols erupted by Mt. Pinatubo in 1991.

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