What might have led to this question:

* The appearance of Mercury: Mercury is a rocky planet with a very thin atmosphere. It's surface is heavily cratered and gray in color. It doesn't have the distinctive features like the white clouds on Venus or the Great Red Spot on Jupiter.

* Confusion with other celestial objects: There are other celestial bodies with white spots, like the Great White Spot on Saturn's moon Titan.

Key takeaway: Mercury does not have any permanent features that could be called a white spot.