Hubble Finds Cloudy, Cold Weather for Mars-Bound Spacecraft

From: (by way of Jan Wee <>)
Subject: Hubble Finds Cloudy, Cold Weather for Mars-Bound Spacecraft
Date: Tue, 20 May 1997 14:40:09 -0500

FYI --

Donald Savage
Headquarters, Washington, DC                         May 20, 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)

Diane Ainsworth
Jet Propulsion Laboratory, Pasadena, CA 
(Phone:  818/354-5011)

RELEASE:  97-100


       As two NASA spacecraft speed toward a mid-year rendezvous 
with Mars, astronomers using the Hubble Space Telescope are 
providing updated planetary weather reports to help plan the missions.  

     Hubble's new images show that the "martian invasion" of 
spacecraft will experience considerably different weather 
conditions than seen by the last U.S. spacecraft to land on Mars 
21 years ago.

       Martian atmospheric conditions will affect the operation of 
both the Mars Pathfinder landing on July 4, and the September 11 
arrival of the Mars Global Surveyor which will map the planet from 
orbit.  Hubble images taken barely three weeks apart, on March 10 
and March 30, reveal dramatic changes in some local conditions, 
and show overall cloudier and colder conditions than Viking 
encountered two decades ago.

       "Because Pathfinder uses the atmosphere to decrease its 
velocity for landing, and because the lander and rover are solar-
powered, understanding the state of the atmosphere prior to 
landing is important," said Dr. Matthew Golombek, Pathfinder 
project scientist at NASA's Jet Propulsion Laboratory, Pasadena, CA.

       "On July 4, Mars Pathfinder will enter the atmosphere 
directly from approach and slow itself behind an aeroshell with a 
parachute, small solid rockets and giant airbags.  The lander 
carries a small rover to explore the surface and investigate the 
kinds of materials present.  Hubble images of Mars are helping us 
to adjust our flight path for landing and effectively plan surface 
operations," said Golombek.

       "It's not the dusty Mars of the Project Viking days (mid 
1970s to early 1980s) or the habitable oasis of science fiction 
stories," says Todd Clancy of the Space Science Institute in 
Boulder, CO.  "We're finding a Mars that's colder, clearer, 
cloudier.  Hubble is rapidly changing our view of Mars' 
environment.  The planet's weather apparently has a flip-side to it."

       Hubble's findings also offer new insights into the 
differences and similarities of weather on the other terrestrial 
planets.  "The planets are similar in many important ways, so the 
very major differences between them are interesting from a 
viewpoint of understanding meteorology better," said team leader 
Phil James of the University of Toledo in Ohio.  "Hubble is 
allowing us to look at Mars in ways never before seen."

       In September, NASA's Mars Global Surveyor will skim across 
the upper martian atmosphere to slow down by friction and enter 
orbit around the red planet.  Atmospheric density is a key factor 
in precisely executing this complex and delicate aerobraking 
maneuver.  Hubble is ideal for tracking regional dust storms which 
could pose a threat to Surveyor by drastically changing the 
planet's air density.  Such storms can cause a tenfold increase in 
the martian atmosphere's drag at 60 miles above the surface.

       Comparing the appearance of Mars to that in earlier 
spacecraft observations, Hubble has found some areas of the 
martian surface that have been changed dramatically by wind-blown 
dust.  The most prominent example is the "classic dark feature" 
called Cerberus, which is roughly the size of California (800 by 
250 miles).  This feature has been seen as a low albedo (dark) 
region by ground-based telescopic observers since early this 
century, and was studied in detail by the Mariner 9 and Viking 
orbiters in the 1970s.  

      In Hubble's view, only three dark splotches remain, probably 
related to dark sand being carried out of craters by the wind.  
The astronomers think that dust storms in the region have covered 
the formerly dark surface with bright dust, effectively erasing 
Cerberus from the map.

       Hubble is ideally suited for long-term study of Mars.  When 
Mars has been closest to Earth, Hubble has resolved surface 
details as small as 25 miles across.  This allows astronomers to 
track subtleties in the shifting cloud patterns and periodic dust 
storms.  This planet-wide "weather satellite" view is 
complementary to the close-up views which will be provided by Mars 
Pathfinder and Mars Global Surveyor.

       The Space Telescope Science Institute is operated by the 
Association of Universities for Research in Astronomy, Inc. 
(AURA), for NASA, under contract with the Goddard Space Flight 
Center. The Hubble Space Telescope is a project of international 
cooperation between NASA and the European Space Agency (ESA). 

EDITOR'S NOTE: Images to accompany this release are available to 
news media representatives by calling the Headquarters Imaging 
Branch on 202/358-1900.  NASA Photo numbers are:

Color:          Mars Clouds          97-HC-315
Color:          Mars N. Pole         97-HC-316
Color:          Mars 4 Sides         97-NC-317

Image files in GIF and JPEG format and captions may be accessed on 
Internet via anonymous ftp from in /pubinfo. 

                               GIF               JPEG
PRC97-15a Mars Clouds    gif/marsbwc.gif   jpeg/marsbwc.jpg 
PRC97-15b Mars N. Pole   gif/marsnpc.gif   jpeg/marsnpc.jpg 
PRC97-15c Mars 4 Sides   gif/mars4op.gif   jpeg/mars4op.jpg 

Higher resolution digital versions (300 dpi JPEG) of the release 
photographs are available in /pubinfo/hrtemp: 97-15a.jpg (color), 
97-15b.jpg (color) and 97-15bbw.jpg (black & white), and 97-15c 
(color) and 97-15cbw.jpg (black & white).

GIF and JPEG images, captions and press release text are available 
via the World Wide Web at and via links in: