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Hubble Watches Mars As Mars Global Surveyor Begins Aerobraking
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- From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
- Date: Wed, 17 Sep 1997 18:25:46 GMT
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FOR RELEASE: September 17, 1997
PHOTO NO.: STScI-PRC97-31
HUBBLE WATCHES THE RED PLANET AS
MARS GLOBAL SURVEYOR BEGINS AEROBRAKING
This NASA Hubble Space Telescope picture of Mars was taken on
Sept. 12, one day after the arrival of the Mars Global Surveyor
(MGS) spacecraft and only five hours before the beginning of
autumn in the Martian northern hemisphere. (Mars is tilted on
its axis like Earth, so it has similar seasonal changes, including
an autumnal equinox when the Sun crosses Mars' equator from
the northern to the southern hemisphere).
This Hubble picture was taken in support of the MGS mission.
Hubble is monitoring the Martian weather conditions during the
early phases of MGS aerobraking; in particular, the detection of
large dust storms are important inputs into the atmospheric
models used by the MGS mission to plan aerobraking operations.
Though a dusty haze fills the giant Hellas impact basin south of the
dark fin-shaped feature Syrtis Major, the dust appears to be localized
within Hellas. Unless the region covered expands significantly, the
dust will not be of concern for MGS aerobraking.
Other early signs of seasonal transitions on Mars are apparent in the
Hubble picture. The northern polar ice cap is blanketed under a polar
hood of clouds that typically start forming in late northern summer.
As fall progresses, sunlight will dwindle in the north polar region
and the seasonal polar cap of frozen carbon dioxide will start
condensing onto the surface under these clouds.
Hubble observations will continue until October 13, as MGS carefully
uses the drag of the Martian atmosphere to circularize its orbit about
the Red Planet. After mid-October, Mars will be too close to the Sun,
in angular separation, for Hubble to safely view.
The image is a composite of three separately filtered colored images
taken with the Wide Field Planetary Camera 2 (WFPC2). Resolution
is 35 miles (57 kilometers) per pixel (picture element). The Pathfinder
landing site near Ares Valles is about 2200 miles (3600 kilometers)
west of the center of this image, so was not visible during this
observation. Mars was 158 million miles (255 million kilometers)
from Earth at the time.
An image of this region of Mars, taken in June 1997, is shown for
comparison. The Hellas basin is filled with bright clouds and/or
surface frost. More water ice clouds are visible across the planet
than in the Sept. image, reflecting the effects of the changing season.
Mars appears larger because it was 44 million miles (77 million
kilometers) closer to Earth than in the September image.
Credit: Phil James (Univ. Toledo) and Steve Lee (Univ. Colorado),
Images are available via the World Wide Web at
http://oposite.stsci.edu/pubinfo/PR/jpeg/mars0609.jpg (JPEG) and via links
Image files also may be accessed via anonymous ftp from oposite.stsci.edu
in /pubinfo: gif/mars0609.gif (GIF) and jpeg/mars0609.jpg (JPEG),
tiff/1997/31a.tif and 31b.tif (TIFF).