There were three biology experiments on the Viking lander 1 and Viking lander 2.

NPR: Revisiting the Viking Missions to Mars

When the Viking lander 1 landed on July 20, 1976, it sent back the first pictures from the surface of Mars.

NPR: Revisiting the Viking Missions to Mars

And if we wanted to fly over the Viking lander, we could.

NPR: Revisiting the Viking Missions to Mars

When we come back we're going to switch gears again and talk about the 30th anniversary of the Martian lander, the Viking, landing on Mars 30 years ago this week.

NPR: Electronics Pioneer William Shockley's Legacy

There have been three successful Mars lander missions, the Viking 1 and Viking 2 in 1976, and the Pathfinder in 1997.

CNN: Mars Pathfinder enlisted in search for lost Polar Lander

The lander was one of two twin Viking spacecraft, each one having two parts.

NPR: Revisiting the Viking Missions to Mars