Frontiers of Science: Dust Storms on Earth and Mars

Dust Storms on Earth and Mars

Have you ever thought of traveling to Mars? Do you think that planet looks anything like earth? For most people, if they could go to Mars, it would probably seem quite strange; but for some there would be one thing to remind them of home—blowing dust!

Dust storms occur in many different parts of the world: China, India, Egypt, Australia, Africa, and even the United States. For many people they are a natural part of their lives; but for others they can be a frightening experience—especially if they are caught outside in one for the first time. In parts of California and Arizona, for instance, cars that are on the highways when a sandstorm strikes often have their paint sandblasted off, and their drivers’ nerves are frayed as well.

Only two major ingredients are needed to create a dust storm—wind and loose surface sand or dust. Thus, strong winds that sweep across large deserts often form huge dust storms. Each year tons of dust from the African Sahara are carried all the way across the Atlantic Ocean and dropped into the eastern Caribbean. And during the years of the famous dust bowl in the United States (1930s), soil from the Plains States often fell upon the cities of the East Coast.

Smaller dust storms occur every year in many parts of the world when cool air from large thunderstorms sweeps out in front of them. This cool air is heavier than the warmer air it flows into, so it rolls along the ground, picking up any available dust. These dust storms usually have a front edge that people describe as a solid wall of dust. It may reach a mile or two into the air and extend 100 miles. The front edge of such a dust storm usually moves about 30 miles per hour; but wind gusts within it may be twice that great.

Dust storms on earth can be very dramatic, but compared to those on Mars they seem rather tame. On that far and windswept world such storms often tower 30 miles above the ground, and they may travel as fast as 300 miles per hour! In addition, Martian dust storms have been observed that expanded to cover the entire face of the planet.

Perhaps the strongest such planet-wide dust storm to occur on Mars in the last hundred years took place in 1971. It was of special interest to scientists, for at that very same time the first earth-launched spacecraft to ever orbit another planet was on its way to Mars. When Mariner IX went into orbit on November 14, the only things that could be seen through the blanket of dust were four dark spots that later turned out to be huge volcanoes. It wasn’t until the end of January 1972 that clear pictures of the surface could be obtained and sent back to earth.

Following Mariner IX, the United States has sent two other important spacecrafts to Mars—Viking I and II. Each of these expeditions included a lander and an orbiting vehicle. The orbiters have photographed several smaller dust storms that appear much like those on earth, plus large areas of sand dunes. The landers, meanwhile, have sent back pictures that show how the surface sands are piled in drifts by the winds at the landing sites.

So, if you would like to know what it is like on Mars—but feel you’d rather not stand in line for a ticket on the first available spaceship—head for a desert here on earth. When the wind is whipping the surface sands into a blizzard of dust, it’s the next best thing to seeing Mars itself.

[photo] Two hours after sunrise on Mars, the camera of the Viking II lander reveals a landscape much like parts of Arizona, California, and Mexico. Winds have been moving the drifts of sand from the upper left to the lower right of the picture. (NASA photo.)

[photo] A dust storm rolls across the plains of central Niger in Africa. The advancing curtain of dust can block out the brilliant rays of the sun in only a matter of minutes. (USDA photo.)

[photos] A 93-mile-wide Martian meteorite crater is shown by the detailed photography of Mariner IX to contain a large field of sand dunes. (NASA photo.)

[photos] Two huge dust storms approach Phoenix, Arizona. For anyone in an airplane or satellite, the city will soon disappear from view. (Photos by Hamilton McCrea III and Con Keyes.)

[photo] A Martian dust storm, much like those of earth, is photographed by the Viking II orbiter in the great Argyre Basin, formed by the impact of a large meteorite early in the planet’s history. Among the mountains to the south of the basin can be seen some of the retreating south polar ice cap. (NASA photo.)