The Viking life experiment

The claim

"NASA's Viking landers detected life on Mars and NASA ignored it."

Where the idea comes from

The Labeled Release experiment's designer, Gilbert Levin, argued for decades that it had found life.

What the evidence shows

1. The experiment added nutrients with radioactive carbon to soil and watched for gas; it did release gas, as microbes would.
2. Viking's other instruments found no organic molecules in the soil, which made life unlikely.
3. In 2008 the Phoenix lander found perchlorate salts in Martian soil. Perchlorates and other oxidants can produce the same reaction without life.

What is still open

A small minority still argues the result was biological. Later missions have found organics on Mars, so the question of past life stays open, but the Viking result itself has a chemical explanation.

Our verdict

Explained Reactive Martian soil explains the result.

Sources

• Viking lander biological experiments (Wikipedia)

Checked 31 October 2026. Spotted a newer source? Tell us.