A pair of eagle-eyed NASA spacecraft — the Mars Global
Surveyor (MGS) and Hubble Space Telescope — are giving
amazed scientists a ringside seat to the biggest global dust
storm seen on Mars in several decades.

The Martian dust storm, larger by far than any seen on Earth,
has raised a cloud of dust that has engulfed the entire
planet for the past three months. As the Sun warms the
airborne dust the upper atmospheric temperature has been
raised by about 80 degrees Fahrenheit. This abrupt onset of
global warming in Mars’ thin atmosphere is happening at the
same time as the planet’s surface has chilled precipitously
under the constant dust shroud.

“This is an opportunity of a lifetime,” said Hubble observer
James Bell of Cornell University in Ithaca, N.Y. “We have a
phenomenal, unprecedented view from these two spacecraft.”

“The beauty of Mars Global Surveyor is that we have almost
two Martian years of continuous coverage and this is the
first time during the mission that we have seen such a
storm,” added Richard Zurek of the Jet Propulsion Laboratory
in Pasadena, Calif.

This storm is being closely watched by the team operating
NASA’s 2001 Mars Odyssey spacecraft, which is heading toward
a rendezvous with the Red Planet later this month. The
Odyssey team plans to “toe-dip” its way into the Martian
atmosphere, gradually deepening its pass through the
atmosphere until the desired drag levels are found. A warm
atmosphere “puffs up,” creating more drag on the spacecraft.

The Thermal Emission Spectrometer on the Global Surveyor has
been tracking the blooming dust storm by measuring
temperature changes that trace the amount and location of
dust in the atmosphere. Both Hubble and MGS caught the storm
erupting in late June, which was unusually early in the
spring of the Martian Northern Hemisphere compared to
previous large storms. Hubble doesn’t have continuous Mars
coverage, but does show the whole planet in a single snapshot
and shows the full range of dust activity from sunrise to

Planetary scientists photograph the entire planet every day
using the Global Surveyor’s Mars Orbiter Camera. This has
allowed them to pinpoint the actual location of places where
dust was being raised, and see it migrate and interact with
other Martian weather phenomena and surface topography. This
also has provided them an unprecedented, detailed look at how
storms start and “blossom” across the orange, arid planet.

“What we have learned is that this is not a single,
continuing storm, but rather a planet-wide series of events
that were triggered in and around the Hellas basin,” said
Mike Malin of Malin Space Science Systems, Inc., San Diego,
lead investigator on the camera. “What began as a local event
stimulated separate storms many thousands of kilometers away.
We saw the effects propagate very rapidly across the equator
— something quite unheard of in previous experience — and
move with the Southern Hemisphere jet stream to the east.”

“By the time the first tendrils of dust injected into the
stratosphere by the initial events circumnavigated the
Southern Hemisphere, which took about a week, separate storms
were raging in three main centers. The most intriguing
observation is that the regional storm in Claritas/Syria has
been active every day since the end of the first week of
July,” said Malin.

After three months, the storm is beginning to wane. The
planet’s shrouded surface has cooled, and this allowed the
winds to die down and the fine dust to begin settling.
However, Mars is approaching the closest point of its orbit
to the Sun. Once the atmosphere begins to clear, the return
of unfiltered solar radiation may trigger additional high
winds and kick up the dust all over again. This “one-two
punch” has been seen in previous Mars storms for centuries.

“Understanding global dust storms, such as that which we have
witnessed this year, is a vital part of the science goals of
the Mars Exploration Program,” said James Garvin, NASA’s lead
scientist for Mars exploration, NASA Headquarters,
Washington. “Such extreme climate events could potentially
provide clues to how climate changes operate on Mars, now and
in the past, and provide linkages to the record of sediments
on the planet.”

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