Mars:
Dastardly Dust
Mars wrote the book on dust.
Red dust. Tons of it. In storms that last for weeks. And it's no wonder.
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A vast storm, nearly four
times the size of Texas, is seen in this 1999 image of Mars. The storm is
made up of swirling arms that rotate counterclockwise around a 200-mile-wide
eye, very similar to an earthly cyclone. IMAGE: NASA
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"With so little
moisture in the soil, sand and dust are always blowing around on Mars,"
said Ingersoll. "Every few years, a global dust storm blots out the Sun
for a few weeks until the dust settles out."
The puzzling thing about
these great storms is that they don't occur every year.
"Without an ocean, there
is nothing on Mars that would make one year much different from any
other," Ingersoll said. "There is no El Nino cycle, for instance. Yet
some years have global dust storms and others don't."
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ANIMATIONS
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 The four images in this animation
were each taken two hours apart on June 30, 1999. They show a dust storm
(brown) gathering near the Martian north pole (the light-colored area above
center).
IMAGES:
NASA/MGS/Malin Space Science System
Animation by SPACE.com
 This Martian dust devil, captured by
the Mars Pathfinder in 1997, is 49 feet wide (15 m) and more than 800 feet
tall (245 m). It was spotted in an area called South Twin Peaks, about 1
kilometer west of where Pathfinder. The storm has a well-defined column with
a tenuous top. The three frames of the animation
were taken about 20 seconds apart. IMAGE: © Stephen Metzger
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Reference
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All About Mars
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And when it comes to
tornadoes, there's no place like Mars.
The typical terrestrial
tornado typically rises no more than 2,000 feet (610 meters) into the
atmosphere (though the storm that spawns it is usually taller). But a Martian vortex,
all by itself, can tower up to 5 miles (8 kilometers).
These Martian dust devils,
as they are called, are actually more similar to those harmless whirling winds
you might see in an open, dusty field on a windy afternoon back home. On both
planets, they form when the ground heats up during the day, warming the air
immediately above the surface. Pockets of warm air rise and interfere with each
other, sometimes causing one pocket or another to begin a swirling motion.
(Tornadoes on Earth have a
different origin altogether. They brew in the border region of large air
masses. Cold air from the north and warm, moist tropical air have a propensity
for getting together along a swath of the Midwest known as Tornado Alley. The
resulting funnels might not be as tall, but they destroy a lot more mobile
homes.)
Our view of Martian weather
has changed dramatically in the past decade. Mars was once thought to have much
quieter weather. But now we see shifting sand dunes, retreating ice caps and
colossal polar cyclones that can be four times the size of Texas.
Strong evidence that no
place on Earth -- not even Texas -- can lay claim to the biggest, baddest
weather in the solar system.
Other news about weather in our solar system
Venus:
No Lightning, But a Strange Green Glow
Jupiter:
Cassini Snaps Earth-like Weather
Jupiter:
Cassini Makes First Color Movie of Clouds
Titan:
Earth-Like Weather and Methane Rain
The Sun: Space
Weather
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