Miranda was a seemingly uninteresting moon whose fascinating features were stumbled upon by accident. Voyager 2's orbit required it to fly close to Miranda. Surprisingly, the quick fly-by revealed that Miranda was more intriguing than we had ever suspected.
Miranda's appearance is what sets it apart from all other moons. Strange grooves, trenches, huge gashes, and other abnormal features litter Miranda's surface. Two huge oval-shaped features called coronae are also present. These coronae are about 300 km long and are surrounded by ridges, giving the appearance of a race track. It looks as if the planet has somehow been beaten up.
So how did Miranda acquire its strange appearance? One theory is that Miranda has been broken apart over and over again, and its pieces have reformed together each time, creating jagged seams and edges. Another possibility is that hot spots under the surface swelled up and burst through the surface, altering its appearance. The most dull, and also the most probable explanation is simply that layers of melted and refrozen ice have molded the shape of the surface into what we see today. Whatever did cause it, it made an interesting moon out of what would have been a very mundane one.
* Photo credit - JPL