This was
your sky.

Burns Cliff on Mars

The majestic walls of Endurance Crater on Mars contain layers of clues about the planet's ancient past. The deeper the layer, the older the clue. This particular crater wall, dubbed Burns Cliff, was imaged by the Opportunity robot rover. Close inspection of different layers has revealed slightly different compositions and interesting trends in relative compositions. For example, deeper layers contain decreasing amounts of both magnesium and sulfur.