For all the triumph of NASA’s 1976 Viking mission, which put two unmanned spacecraft on Mars, there was one major disappointment: The landers failed to find carbon-based molecules that could serve as the building blocks of life.

The complete lack of these organic molecules was a surprise, and the notion of a desolate, lifeless Mars persisted for years.

Now, some scientists say that conclusion was premature and perhaps even incorrect. They suggest that such building blocks  known as organic molecules, although they need not come from living organisms  were indeed in the soil, but that they were inadvertently destroyed before they could be detected.

If true, that could cast the scientific conclusions of the Viking mission in a new light, especially since another Viking experiment claimed to have found living microbes in the soil. Most scientists discounted that possibility  how could there be life in soil devoid of the building blocks of life?