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0812.PR
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1993-04-23
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OFFICE OF PUBLIC INFORMATION
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA. TELEPHONE (2l3) 354-50ll
FOR IMMEDIATE RELEASE March
3l, l977
While preparing Viking Lander 2 for the fast
approaching
Martian winter, flight controllers at Jet Propulsion
Laboratory
are working on a new problem: the lander's sampler arm
stopped
while trying to pick up soil for the final biology
experiment.
Instead of picking up soil, the sampler shut down
about
midway through its sequence. The collector head is pointing
directly at camera l.
Engineers are diagnosing the problem. When they
complete
that work, they will stow the boom until Martian spring, when
they
will try to reactivate it. Meanwhile, all soil sampling
activities
have been suspended.
A final planned Lander 2 biology experiment has
been
cancelled. During that experiment the soils were to have
been
incubated at much colder temperatures than had been used in
earlier experiments. Heaters were turned off during the soil
îacquisition sequence that failed. They are still off, and
nutrient
in two experiments has frozen.
However, the heaters will be turned on again March
3l,
and about April 2l, scientists will start a sequence to do
two
experiments on the soil already in the instruments from
previous
soil tests. Gas exchange will heat the soil several times
and
analyze resulting gas changes in a further attempt to
understand
the chemistry of the Martian soil.
-more-
-2-
Labeled release will inject nutrient onto a larger
than
normal (approximately 2.2 cc instead of 0.5 cc) amount of
soil.
The objective is to try to understand if it is the quantity
of
soil tested that limits the size of the strong responses seen
in
earlier cycles.
Meanwhile, temperatures at Utopia Planitia, where
Viking
Lander 2 touched down last Sept. 3, are nearing the frost
point
of carbon dioxide, the lowest experienced on Mars. The
critical
îtemperature is -l23 degrees Celsius (-l90 Fahrenheit). That
compares with the relatively balmy daily highs of -25 to -30
Fahrenheit recorded during the primary mission.
Viking Lander 2's science duties are being reduced
in hopes of surviving the bitter winter.
From April 8 through l4 a series of commands will
be
sent to Viking lander 2 to collect reduced scientific
information.
The survival mission will begin April l7. All remaining
power
will run heaters in an attempt to maintain survivable
temperatures
inside the lander.
The meteorology station and the seismic instrument
will
continue to gather data through the winter. The cameras will
take
occasional pictures, looking for growth of carbon dioxide
frost
on the surface and on the spacecraft. The inorganic soil
analysis
instrument will run periodic tests, too, on the chance that
some
windblown dust will enter the open funnel. The
organic-analysis
experiment will be turned off April 5. All other experiments
will
be suspended until Martian spring.
-more-
î
-3-
As long as sunlight shines strongly on the Martian
surface and no frost forms, temperatures remain above the
frost
point of carbon dioxide. But when an overnight layer of ice
forms, it reflects much of the early-morning sunlight back to
space; surface (and lander) temperatures then fall rapidly.
High-altitude water-ice clouds and atmospheric dust
help
screen out sunlight, accelerating the plunge below safe
operating
levels.
Unlike snow on Earth, which is frozen water vapor
(a
minor constituent of our atmosphere), snow on Mars is mostly
frozen carbon dioxide, about 95 per cent of the Martian
atmosphere.
Water freezes at Earth's surface at 0 degrees Celsius (32
degrees
Fahrenheit); carbon dioxide freezes at the Martian surface at
-l90 F. That is colder than the spacecraft was designed to
survive.
Scientists predict winter will begin sometime after mid-April
and last until about mid-October. By the end of June, they
say,
frost should stay on the ground throughout the day. A layer
of î
frost may even coat parts of the lander itself.
Viking Lander 2 is located about 48 degrees north
latitude,
roughly equivalent to the United States-Canada border.
Scientists
believe the Martian north polar ice cap may spread that far
south.
The severe winter cold is expected to have little
effect
on Viking Lander l. It is in the Chryse basin within the
Martian
tropics -- about the same latitude as Honolulu, on Earth.
Viking is managed for NASA by Langley Research
Center,
Hampton, Va. G. Calvin Broome is mission director for the
Viking
Extended Mission, scheduled to continue through May l978.
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