The Viking results imply that there is no life on the surface of Mars.
Conditions there are too cold, too dry and too oxidizing.
This may be true, but beneath the surface things might be quite different. The absence of liquid water, the result of low atmospheric pressure and low temperatures, makes the surface of Mars particularly inhospitable. Below the surface, with the weight of the overlying soil, obtaining pressures suitable for liquid water to exist would be no problem. The density of cosmic ray tracks in the meteorite's lava crystals suggests that lava flowed on the surface of Mars about 200 million to 400 million years ago. The other martian meteorites are between 200 million and 1 billion years old.