On August 6 2012, one of NASA's most sophisticated mobile analysis units, the Curiosity Rover landed on mars in order to analyse the chemical composition of its surface soil. The mission was designed to teach us more about what the red planet is currently made of, and more importantly what is WAS made of. Since the discovery of eroded valleys suggest that there once might have been flowing water (perhaps even VERY recently).
Last week NASA published the information that Curiosity has gathered and interpreted so far, and there's a lot, enough for 5 separate papers. Most interestingly, the papers report water found in the composition of the soil collected by Curiosity in certain places.
It's important to stress at this point that this isn't free flowing water in liquid form, but rather water molecules found as part of the rock which makes up the surface. The mineral is known as "mugearite", and the samples were found to be particularly rich around a martian volcano called "Jake_M" (named after a NASA engineer). The soils composition is said to be around 2% water by mass, this is even greater evidence to what is now well accepted to be that Mars was once a planet with flowing water and oceans.
For me at least, the coolest part of this is how the sample data was actually analysed by Curiosity. The Rover has a built in unit known as SAM (Sample Analysis Mars), which chemists and geochemists will know as a Microanalysis unit. Essentially samples are collected, heated up to rather silly temperatures, and the vapour which results is measured for its mass. I've actually used a piece of equipment like this, which is probably why I find it particularly amazing that Curiosity can do it in space, without oxygen in the atmosphere.
A number of other volatile components of the soil were also discovered by Curiosity, in particular carbon dioxide, sulphur dioxide and oxygen molecules.