|
Viking 1 reached Mars orbit
on 19 June 1976 when images were taken to locate a suitable
landing site: Chryse Planitia. The orbiter's path was adjusted
several times in order to obtain close-up images of Mars"
satellites, Deimos and Phobos, and to observe different aspects
of the martian surface.
Viking 2 reached Mars orbit
on 7 August 1976, and landed the following month on Utopia
Planitia.
The orbiters were equipped
with two television cameras, an infrared spectrometer to map
the distribution of water vapour and a radiometer for determining
temperature distribution. The landers sampled the upper atmosphere
during descent, made meteorological measurements and carried
out experiments on samples of martian soil. One of the prime
objectives was to test for the presence of organic material
which might indicate the existence of life, but nothing 'concrete'
was found.
Thousands of images were returned
from both the orbiters and landers. The whole of the martian
surface was mapped to a resolution of 150-300 metres. The
Viking 1 orbiter operated until 7 August 1980, and the Viking
2 orbiter until 25 July 1978.
The landers ceased operating
in November 1982 and February 1980, respectively. The mission
was regarded as very successful, and it had greatly exceeded
its expected lifetime. The results from the Viking experiments
showed us volcanoes, lava plains, immense canyons, cratered
areas, wind-formed features, and evidence of surface water
are apparent in the Orbiter images.
The planet appears to be divisible
into two main regions, northern low plains and southern cratered
highlands. Superimposed on these regions are the Tharsis and
Elysium bulges, which are high-standing volcanic areas, and
Valles Marineris, a system of giant canyons near the equator.
The surface material at both
landing sites can best be characterized as iron-rich clay.
Measured temperatures at the landing sites ranged from 150
to 250 K, with a variation over a given day of 35 to 50 K.
Seasonal dust storms, pressure changes, and transport of atmospheric
gases between the polar caps were observed.
From Viking results it is
believed that Mars was once similar to the Earth with a thicker
atmosphere that allowed water to flow on the surface. This
possibly meant that long ago, when Mars was warmer, tiny cells
may have formed which hibernated as the climate cooled (again,
these have not been found as yet).
Mission
Results:
- The orbiters did detailed mapping, beamed
back television pictures, and investigated the global properties
of the atmosphere.
- The landers were the first successful Mars
landers (after the disappointment of the earlier Soviet
lander). Their experiments studied the weather, photographed
the surface, and investigated the physical, magnetic, chemical
and biological (they didn't find anything biological!) properties
of the surface layer
- Using mechanical arms, the landers collected
soil samples. Nutrients were added in an attempt to revive
any cells. Initial results looked promising, but later ones
weren't (as I keep saying).
In conclusion, life (past
or present) on Mars cannot be ruled out, but no definite signs
of organic activity were found, and the general opinion now
is that Mars is sterile at the present time.
|
|
