From: NASANews@hq.nasa.gov (by way of Jan Wee <jwee@mail.arc.nasa.gov>)
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
HUBBLE FINDS CLOUDY, COLD WEATHER CONDITIONS FOR MARS-BOUND SPACECRAFT
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 oposite.stsci.edu 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
http://oposite.stsci.edu/pubinfo/PR/97/15.html and via links in:
http://oposite.stsci.edu/pubinfo/Latest.html
or
http://oposite.stsci.edu/pubinfo/Pictures.html