Earth's moon transiting the sun
Our moon is one of the largest satellites in the solar system, which is impressive considering how much smaller the Earth is compared to Jupiter or Saturn. It has a diameter of 2,160 miles, as opposed to 3,280 miles, the diameter of Jupiter's Ganymede, the largest satellite. Most experts agree that the moon formed when a Mars-sized planet collided with Earth several billion years ago. The ensuing debris cloud reformed into the moon. Here the moon is seen in a NASA composite image transiting the sun from the STEREO-B spacecraft.