Earlier today it was announced the a clay like substance was found on Mars, providing evidence the a drinkable water with PH similar to ours may have existed on Mars at one time.
http://phys.org/news/2013-06-astrobiolog...d.html#jCp
Quote:"Earth and Mars used to have much more in common than they do today. Over time, Mars has lost a lot of its atmosphere and surface water, but ancient meteorites preserve delicate clays from wetter periods in Mars' history. The Martian clay we studied is thought to be up to 700 million years old. The recycling of the Earth's crust via plate tectonics has left no evidence of clays this old on our planet; hence Martian clays could provide essential information regarding environmental conditions on the early Earth."
http://phys.org/news/2013-06-astrobiolog...d.html#jCp