From Unplgged:

Dutch artist Helmut Smits somehow came upon the decision to burn an almost 3-foot by 3-foot square of ash into the grass somewhere out there in the world in the name of art in public places. When it’s viewed from 1 kilometer above the ground (3,280 feet), it looks just like a dead pixel on your monitor at home.

We don’t think anyone has found it yet, so happy hunting!