text: I am just worried that if we investigate too much, Mars will attack!  Oh my.  \n\nSeriously tho, or as serious as I can get, I have read that they have found great quantities of frozen hydrogen just under the soil.  The interesting thing about frozen hydrogen is that it is the basis for water.  Perhaps if Mars ever did have a "thick" atmosphere, when it was ripped away, the oxygen "boiled" out and all that was left was the hydrogen.