|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|
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: