The 1976 Viking lander would have likely found water ice on Mars if it had probed just 4 inches deeper.
NASA’s Mars Reconnaissance Orbiter has revealed frozen water hiding just below the surface of mid-latitude Mars. The spacecraft’s observations were obtained from orbit after meteorites excavated fresh craters on the Red Planet.
Water ice, never seen before in Mars’ “temperate” zone, was discovered in a shallow crater that was made in 2008. The ice reveals that Mars was warmer and wetter in the relatively recent past.
The finds indicate water-ice occurs beneath Mars’ surface halfway between the north pole and the equator, a lower latitude than expected in the Martian climate.
This ice is a relic of a more humid climate from perhaps just several thousand years ago.
said Shane Byrne of the University of Arizona, Tucson.
Mars has large variations in its tilt that cause its climate to change even more strongly that the changes from glacial to interglacial on earth. However, Mars lost most of its atmosphere to space because Mars lacks the mass (size) to hold on to its upper atmosphere when it interacts with energetic particles in the solar wind. With only 1% of the atmospheric pressure of the earth, the Martian surface is uninhabitable to humans.