Evidence grows for liquid water on Mars
Is there still liquid water on Mars? That has been one of the longest-running and most debated questions about the Red Planet. Mars has tons of water, but it is frozen in the polar ice caps and in extensive regions of permafrost underground around the planet. The thin atmosphere does contain water vapour – enough for clouds, fog, frost and snow, but it is too thin and cold for liquid water to exist on the surface.
There might be one exception however. It’s been postulated that small amounts of salty liquid water brines could persist on the surface for short periods of time. The salts allow the water to remain liquid despite the thin atmosphere (and less atmospheric pressure) and cold temperatures. Experiments on Earth have supported this idea.
They may have even been observed directly by the Phoenix lander which landed in the Martian arctic near the north pole – small droplets were seen forming on one of the lander’s legs after landing which had the appearance of water droplets. They grew, merged and slowly moved down the leg before sublimating. Phoenix wasn’t able to analyze them directly, but they looked and behaved like briny water droplets, and the soil, like in other places on Mars, was found to contain both water ice and salts. The theory is that heat from the spacecraft caused the droplets to form, possibly from the exhaust during the landing itself.