Don Savage
Headquarters, Washington, DC                 July 1, 1997
(Phone:  202/358-1547)

Tammy Jones
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5566)

Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone:  410/338-4514)

RELEASE:  97-148

HUBBLE'S LOOK AT MARS SHOWS CANYON DUST STORM,
CLOUDY CONDITIONS FOR PATHFINDER LANDING

     Hubble Space Telescope pictures of Mars, taken on June 27 in
preparation for the July 4 landing of the Pathfinder spacecraft,
show a dust storm churning through the deep canyons of Valles
Marineris, just 600 miles (1000 km) south of the Pathfinder
spacecraft landing site.

     "Unless the dust storm were to evolve into a massive, global
event, its effects on the Pathfinder mission should be minimal,"
says Steve Lee of the University of Colorado in Boulder.  "This is
something we did not expect to see."

     The Hubble astronomers also report the presence of patchy
cirrus clouds over the landing site and very thick clouds to the
north.  Since there are so many clouds (related to low
temperatures in the atmosphere causing water vapor to freeze), the
dust will probably stay confined to the canyons, they conclude.

     If dust rises to the elevations where the water-ice clouds
form, ice condenses on dust grains and the heavier ice/dust
particles quickly fall back out of the atmosphere.  Though the
dust could extend at low altitudes over the landing site,
researchers say current prevailing winds should not take the dust
northward.

     "If dust diffuses to the landing site, the sky could turn out
to be pink like that seen by Viking," says Philip James of the
University of Toledo.  "Otherwise, Pathfinder will likely show
blue sky with bright clouds."

     The imaging team includes Steve Lee of the University of
Colorado at Boulder's Laboratory for Atmospheric and Space
Physics; Todd Clancy of Boulder's Space Science Institute; Phillip
James of the University of Toledo; Mike Wolff of the Space Science
Institute; and Jim Bell of Cornell University.

                          -end-