Timeline (Habitable Mars)

1947- The Lowell Observatory using a new spectrographic telescope determines the presence of oxygen in the Martian atmosphere.

20 July 1965- "Mariner-II" passes within 10,000 kilometers of Mars. It returns pictures of an arid, but habitable world. Large swathes of lichen and even grass-like plant life is seen, and the detection of a oxygen/nitrogen atmosphere at breathable pressure levels.

27 November 1971- "Mars-2", a Soviet probe, crashes on the surface of the planet. Apparently its parachute failed to open, but it does become the first man-made object on the Red Planet.

2 December 1971- "Mars-3", a similar probe from the USSR, makes a soft landing on the Chryse Planitia. After transmitting a single photo of the surface, it fails due to a computer glitch. The single photo shows a landscape similar to America's Southwest.

20 July 1976-  "Viking-1" makes the first successful soft landing of a probe on Mars. It takes color photos of the planet, including close-ups of both plant life and a single hexapodal insect which landed on its camera test target. Soil samples analyzed showed proof positive of fertile soil and a breathable atmosphere.