SOLAR SYSTEM

Detailed explanation-1: -While it found no traces of life, Viking 1 did help better characterize Mars as a cold planet with volcanic soil, a thin, dry carbon dioxide atmosphere and strking evidence for ancient river beds and vast flooding.

Detailed explanation-2: -In the LR experiment, both the Viking 1 and Viking 2 landers collected samples of Martian soil, injected them with a drop of dilute nutrient solution, and then monitored the air above the soil for signs of metabolic byproducts.

Detailed explanation-3: -The 1976 Viking Labeled Release (LR) experiment was positive for extant microbial life on the surface of Mars. Experiments on both Viking landers, 4000 miles apart, yielded similar, repeatable, positive responses.

Detailed explanation-4: -Is there life on Mars? One former NASA scientist said we found evidence of such more than 40 years ago. In an essay for Scientific American, Gilbert V. Levin explained how life-detection equipment aboard the Viking mission to Mars in 1976 reported positive results for evidence of life.

Detailed explanation-5: -These experiments discovered unexpected and enigmatic chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in soil near the landing sites.

Detailed explanation-6: -When Viking 1 and 2 touched down on Mars in 1976, each carried several instruments to study the planet and look for signs of life. The Labeled Release experiment mixed small samples of Martian soil with drops of water containing a nutrient solution and some radioactive carbon.