GeoMedia: Indisputable evidence of water on Mars!!

The Mars rover Opportunity has found indisputable evidence that water existed on Mars in the form of a vein of the mineral gypsum in bedrock! The vein is about twice the width of a human thumb and half a metre long. This is first direct proof that water existed on Mars and had flowed through a fracture in the rock depositing the gypsum.

This false-color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. Image Credit: NASA/JPL-Caltech/Cornell/ASU

Gypsum (CaSO4·2(H2O)) is a mineral that is commonly found on Earth often in exactly the same situation as it has been found on Mars. The formation of this vein was likely due to groundwater saturated in calcium and sulphate flowing through a fracture in the bedrock. The highly saturated groundwater then precipitated the gypsum, filling in the fracture and leaving behind a vein of gypsum. Precipitation from water is the only possible way that such a structure could have formed and is the way veins of minerals form on Earth. While this sort of feature is relatively common on Earth, this is the first time it has been seen on Mars. The source of the calcium in the water is believed to be from volcanic rocks that were leached by groundwater. The suphur is likely also from volcanic rocks or volcanic gases that were dissolved in the water as well.

This is not the first time gypsum has been found on Mars as previously gypsum sand dunes had been discovered. However, this is the first time that it has been found in-situ, or where it formed, as opposed to having been eroded and then transported by wind as was the case with the dunes. This means that liquid water actually flowed through this fracture!

For more details here is the link to the NASA article: 

http://www.jpl.nasa.gov/news/news.cfm?release=2011-377&cid=release_2011-377#2

Matt