1976

Martian Meteorology


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For an atmospheric scientist, it was the next best thing to being there. In 1976, the Viking Lander set down on the surface of the red planet and began beaming data about Martian weather back to earth.

UW atmospheric scientists James E. Tillman and Conway B. Leovy and colleagues developed capabilities needed to collect and analyze the first, multi-year data set on the meteorology of Mars. Their efforts have led to major discoveries about the weather of our neighbor in space.

Tillman and Leovy were part of the Meteorology Science Team for the Viking Missions to Mars. Weather observations taken on the surface have revealed a stunning array of meteorological phenomena, including frontal systems and great dust storms.

The similarities between terrestrial and Martian frontal systems was greater, in fact, than scientists expected. Fronts refer to the boundaries between air masses of different densities and pressures, and are familiar as the lines drawn on weather maps in the evening television news forecast.

Tillman and colleagues derived a better understanding of the great dust storms that periodically rage over the red planet. They discovered oscillations in the Martian air pressure on the scale of Martian days ("sols") that appear to build and help trigger the tempests.

Tillman and colleagues in the Department of Statistics also developed a simple mathematical model of how the air pressure varies annually due to the cyclical condensing and evaporating of carbon dioxide in the polar caps as the Martian seasons progress. Carbon dioxide in the solid state is what we commonly call "dry ice" and can pass directly from solid to gas back to solid with heating and cooling, without going through the liquid state, in a process that scientists call "sublimation."

With the aid of programmers from the NASA Jet Propulsion Lab, Tillman and staff processed raw data from the Viking spacecraft, both for UW scientific analysis and for mission controllers at JPL. For over 1,000 days, this was JPL's only information source and a "first" for the operational processing of a planetary spacecraft by a non-governmental institution. A real-time link was created and implemented to assist in spacecraft operations; it served later as the basis for a permanent exhibit opened in 1983 at the Smithsonian National Air and Space Museum exhibit in Washington, D.C.

Of all the planets, Mars most closely resembles earth in its meteorology. For those who dream of manned missions to Mars, the weather, just as here on earth, will be a factor with which visitors will have to contend. Mission planners would have to select satisfactory sites and seasons for visits to Mars. Global dust storms would pose the problem of sand and dust abrasion, and advanced warning would be needed in order to erect shelters and take cover. Storms and clouds would also cool the surface quickly, owing to loss of solar radiation. One day, perhaps, the discoveries made by these UW researchers will be key in warning space travelers on Mars when they'll need their "bumbershoot."

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