Evidence for AND AGAINST

Over the years, several clues have suggested Martian life, while other indications are against it

- 

AGAINST

BARELY INSIDE THE HABITABLE ZONE

While Earth sits in the middle of the ringlike zone-around the Sun where life is theoretically possible, Mars is right on its outer edge.

AGAINST

INHOSPITABLE ENVIRONMENT

Martian surface conditions are much colder and drier than Earth's, while the very thin atmosphere shows no signs of modification by biological processes.

AGAINST

HIGH LEVELS OF RADIATION

Without the same kind of protective magnetic field as Earth, Mars is exposed to much more intense cosmic radiation - around 700 times higher than our planet.

AGAINST

TOXIC SOIL