NASA MRO Image of Mars: Mineral Veins
The bright linear features cutting the bedrock in the center region of this image look like mineral veins. Mineral veins are sheetlike bodies of minerals formed by water that flows through fractures.
The setting of this image is the central uplift of a large (approximately 50-kilometer diameter) impact crater, where deep, ancient bedrock was uplifted about 5 kilometers and fractured.
Heat from the impact melted ice in the Martian crust, creating a hydrothermal system. This could have been a habitable environment. A small mineral vein was recently discovered by the Opportunity rover at Endeavour Crater.