For more information contact:

Nancy Neal
NASA Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-0039)

For more information on Mars click on this link.

Caption for Image One: Two dramatically different faces of our
Red Planet neighbor appear in these
comparison images showing how a global dust storm engulfed Mars with the onset of Martian spring in the Southern Hemisphere. When NASA's Hubble Space Telescope imaged Mars in June, the seeds of the storm were caught brewing in the giant Hellas Basin (oval at 4 o'clock position on disk) and in another storm at the northern polar cap.

When Hubble photographed Mars in early September, the storm had already been raging across the planet for nearly two months obscuring all surface features. The fine airborne dust blocks a significant amount of sunlight from reaching the Martian surface. Because the airborne dust is absorbing this sunlight, it heats the upper atmosphere. Seasonal global Mars dust storms have been observed from telescopes for over a century, but this is the biggest storm ever seen in the
past several decades.

Mars looks gibbous in the right photograph because is it 26 million miles farther from Earth than in the left photo (though the pictures have been scaled to the same angular size), and our viewing angle has
changed. The left picture was taken when Mars was near its closest approach to Earth for 2001 (an event called opposition); at that point the disk of Mars was fully illuminated as seen from Earth because Mars was exactly opposite the Sun.

Both images are in natural color, taken with Hubble's Wide Field Planetary Camera 2.

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All stories found on a Top Story page or the front page of this site have been archived from most to least current on this page.

For a list of recent press releases, click here.

October 11, 2001 - (date of web publication)

SCIENTISTS TRACK "PERFECT STORM" ON MARS

	Image 1

A pair of eagle-eyed NASA spacecraft -- the Mars Global Surveyor (MGS) and Hubble Space Telescope -- are giving amazed scientistsa 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 sunset.

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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