False Positive

This month marks the 40th anniversary of the landing of the Viking spacecraft on Mars back in 1976. There were two landers about the size of golf carts that took the first clear images of the Martian surface. They analyzed rocks and tried to determine if there were any active microbes in the Martian soil.
At first, the results showed a positive response but later scientists determined those results were the product of an unexpected inorganic reaction. For some scientists, those results are still questionable.

The next mission to Mars, the Mars 2020 mission will include a sample return component bringing Martian rock to Earth for us to analyze here. Russia had sent a station in 1971 that landed successfully but stopped communicating just 14.5 seconds after reaching the surface.

Image: NASA/USGS