A Day in Astronomy: Viking 1 Begins Obit of Mars

Image (Credit): Viking orbiter spacecraft. (NASA/National Space Science Data Center)

On this day in 1976, NASA’s Viking 1 spacecraft began its orbit of Mars. Launched in August 20, 1975, it took the Viking 1 spacecraft 11 months to travel to Mars. Viking 1 was a combination of orbiter and landing craft. The attached lander did not land on the Martian surface until July 20th, setting down on the western slope of Chryse Planitia (the Plains of Gold).

The Viking 1 orbiter operated successfully for four years, circling Mars 1,489 times. In addition to orbiting Mars, the orbiter also approached the Martian “moon” Phobos to learn more about the captured asteroid.

As with other missions at the time, there was a Viking 1 and a Viking 2. Viking 2 also had an orbiter and lander, both of which operated successfully.

The Viking missions greatly expanded our knowledge of Mars and its “moons.” In NASA’s fact sheet we learn that the two orbiters sent back 52,000 photographs (and mapped 97 percent of the Martian surface) and the landers sent back 4,500 photographs. Some of the discoveries include:

  • The permanent north cap is water ice; the southern cap probably retains some carbon dioxide ice through the summer.
  • Water vapor is relatively abundant only in the far north during the summer, but subsurface water(permafrost) covers much if not all of the planet.
  • Northern and southern hemispheres are drastically different climatically, because of the global dust storms that originate in the south in summer.

NASA has been back to the Martian surface many times since this first set of missions, but nothing can surpass the initial excitement of Viking missions.