Mercury is the planet closest to the Sun, small and with little surface detail visible from the Earth. Because it is so close to the Sun, it is never far from it in the sky, and we see it always as a morning or evening object.

Mercury transit, UT 2006.11.08 20:32. Imaged with a Canon 300D on a 300mm SCT at f/10, with a 100mm aperture Baader white light filter. Exposure 1/60 second at ISO 200. False color added. Click on the image for a larger version. A large sunspot is visible on the limb at the left, and the small dot to the right is Mercury.