Mars Viking 1 and the Search for Life
Definite Positive Response for Life

 

Mars Viking 1 and the Search for Life
Definite Positive Response for Life 

Viking carried a biology experiment whose purpose was to look for life. The Viking biology experiment weighed 15.5 kg (34 lbs) and consisted of three subsystems: the Pyrolytic Release experiment (PR), the Labeled Release experiment (LR), and the Gas Exchange experiment (GEX).

In addition, independent of the biology experiments, Viking carried a Gas Chromatograph/Mass Spectrometer (GCMS) that could measure the composition and abundance of organic compounds in the martian soil.

The soil resembled those produced from the weathering of basaltic lavas. The tested soil contained abundant silicon and iron, along with significant amounts of magnesium, aluminum, sulfur, calcium, and titanium.

Trace elements, strontium and yttrium, were detected. The amount of potassium was one fifth the average for the Earth's crust.

Some chemicals in the soil contained sulfur and chlorine that were like those remaining after the evaporation of sea water.

The Viking results were surprising and interesting: the GCMS gave a negative result; the PR gave a negative result, the GEX gave a negative result, and the LR gave a positive result.

"Our (LR) experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons"

Viking scientist Patricia Straat recently stated, "Our (LR) experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons."


Most scientists now believe that the data were due to inorganic chemical reactions of the soil; however, this view may be changing after the recent discovery of near-surface ice near the Viking landing zone.

Some scientists still believe the results were due to living reactions. No organic chemicals were found in the soil.

However, dry areas of Antarctica do not have detectable organic compounds either, but they have organisms living in the rocks.

Mars has almost no ozone layer, unlike the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals.

The Phoenix Lander discovered the chemical perchlorate in the Martian Soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface.

If it is widespread on Mars, carbon-based life would be difficult at the soil surface.
 
Viking 1 was the first of two spacecraft sent to Mars as part of NASA's Viking program to search for life on the surface of Mars.

Following launch using a Titan/Centaur launch vehicle on August 20th, 1975 and a 10-month cruise to Mars, the orbiter began returning global images of Mars about 5 days before orbit insertion.

The Viking 1 Orbiter was inserted into Mars orbit on June 19th, 1976 and trimmed to a 1513 x 33,000 km, 24.66 h site certification orbit on June 21st.



Landing on Mars was planned for July 4th, 1976, the United States Bicentennial, but imaging of the primary landing site showed it was too rough for a safe landing.

The landing was delayed until a safer site was found. The lander separated from the orbiter on July 20th, 08:51 UT and landed at 11:53:06 UT.

It was the first attempt by the United States at landing on Mars.