Viking I and Viking 2
Orbiters
Launch:
August 20, 1975 (Viking 1); September 9, 1975 (Viking 2)
Arrival: June 19, 1976 (Viking 1); August 7, 1976 (Viking
2)
Landing: July 20, 1976 (Viking 1); September 3, 1976 (Viking 2)
Mass: 576 kilograms (1,270
pounds)
Science instruments: Biology instrument, gas chromatograph/mass spectrometer, X-ray fluorescence spectrometer,
seismometer, meteorology instrument, stereo color cameras, physical and magnetic properties of soil, aerodynamic properties
and composition of Martian atmosphere with changes in altitude
(http://mars.jpl.nasa.gov/missions/past/viking.html)
The Viking class remote sensing mission are a great leap forward
from Mariner in size and scope. Both missions were launched within a few weeks of each other in August
and September of 1976. Each Viking spacecraft was comprised of two main parts, the orbiter and the lander.
These craft
were also large owing in large part to the mission. The orbiter weighed over 5,000 pounds fully fueled.
The fuel was used for attitude control over the life of the mission. The Orbiter’s body was
over 10 feet high and 8 feet wide, 32 feet from one end of the solar panel to the other. The Orbiter carried
the lander to Mars for release. The Orbiter was to remain in low Mars orbit to relay information to and
from the lander and to take pictures of the Martian surface.
While NASA did have experience with landing powered unmanned craft on the moon. The Viking Lander was the first to
settle on another planet. The lander was large and complex as well. Viking’s
Lander was 7 feet tall and 10 feet wide with three study A-frame legs. It housed cameras, communication,
decent fuel, soil and biologic testers.
Both Viking spacecraft made it to Mars and both Landers descended safely to the surface. Viking
1 landed on 22°N, 48°W in Chryse Planitia, the Plains of Gold and Viking 2 at 48°N, 226°W, a spot in
Utopia Planitia. Both sites are on the broad flat northern plains. These were big spacecraft
that cost big money and made significant discoveries.
So what did they find? One of the most controversial tests was for biologic molecules and possible
life in the surface soil. The test was designed to scoop up some soil and performed tests.
If the test had a certain result and was positive it showed biologic activity. It was positive.
When scientist began thinking about what was actually going on the conclusion by most was the result was caused by
another process, not life.
It
is generally accepted that Mars surface soil is sterile. The unabated solar radiation, the dryness
and the oxidizing characteristics of the soil make it impossible for life to exist there. Mars shows
less organic molecules in the soil than the moon!
Viking found that nitrogen is a large
part of Mars’ atmosphere. Atmospheric pressure varies by up to 30 percent over the course of the
years attribute to CO2 condensing and subliming at the poles. The north pole is water, the south is mostly
CO2. Mars has seasons like Earth only longer since the orbit is much farther out than Earth.
The temperature can get above zero in the midsummer near the equator and can be as low as -180 in winter, near the
condensation point of CO2. The Viking landers photographed CO2 frost in the winter months.
Martian winds had gusts up to 74 miles per hour, the average was much lower. The big dust storms
orginate in the southern hemisphere and spread over the planet. The landers took over 4,500 photographs
and the Orbiters over 52,000. These photos provided a great deal of new information about surface
features.
