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Let's Talk About: Dust devils on Mars
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NASA's Curiosity rover landed at Gale Crater on Mars at the end of the Martian winter. With summer just a few weeks away, mission scientists are hoping the rover will soon encounter dust devils, those swirling tornado-like columns of dust.
Surface temperatures vary greatly on Mars. They can dip to minus 200 degrees Fahrenheit at the poles overnight during the winter, or they can climb to a balmy 70 degrees Fahrenheit during a Martian summer day. It's the warm surface temperatures that bring alive the Martian dust devils.
Martian dust devils form the same way they do in deserts on Earth, when the ground temperature is hotter than the air above it. If you were standing on Mars, the temperature at your feet could be 32 degrees Fahrenheit while the temperature at your nose could be minus 32 degrees Fahrenheit.
Dust devils form when heated less-dense air close to the ground rises and pushes through the layer of cooler denser air above. The rising plumes of hot air and the falling plumes of cool air begin circulating vertically in convection cells. When a horizontal gust of wind blows through the convection cells, they begin spinning horizontally, forming a vertical column and starting a dust devil.
Hot air rising through the center of the column propels the spinning air to speeds of up to 70 miles per hour. As these monster columns, 10 times larger than any tornado on Earth, begin scouring the ground with sand, they create fine dust. The central column of hot rising air propels that dust high into the sky. Because some Martian dust devils can tower up to 6 miles high, planetary meteorologists believe that some dust devils could spin up into massive dust storms that can cover the planet.
Curiosity is equipped with a sophisticated weather station that will examine how Martian dust devils form and why some evolve into massive dust storms.
First Published October 4, 2012 12:00 am
