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Prominent mineral veins at the "Garden City" site examined by NASA's Curiosity Mars rover vary in thickness and brightness, as seen in this image from Curiosity's Mast Camera (Mastcam).
The image covers and area roughly 2 feet (60 centimeters) across. Types of vein material evident in the area include:
1) thin, dark-toned fracture filling material;
2) thick, dark-toned vein material in large fractures;
3) light-toned vein material, which was deposited last.
Figure 1 includes annotations identifying each of those three major kinds and a scale bar indicating 10 centimeters (3.9 inches).
Researchers used the Mastcam and other instruments on Curiosity in March and April 2015 to study the structure and composition of mineral veins at Garden City, for information about fluids that deposited minerals in fractured rock there.
Malin Space Science Systems, San Diego, built and operates Curiosity's Mastcam. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, built the rover and manages the project for NASA's Science Mission Directorate, Washington.