We are only weeks away from Christmas and Saturn’s moons Dione and Rhea have gotten into the Christmas spirit by aligning perfectly to create a snowman. This photo was captured by the now deceased Cassini spacecraft but has only now been released. These two moons are very far from each other, and the reason they look roughly the same size is a trick of perspective.
At the time the photo was snapped Dione, the head of the snowman, was 685,000 miles from Cassini while Rhea was 995,000 miles from Cassini. The two moons aren’t the same size as they appear in the image. Dione is smaller with a diameter of 698 miles.
Rhea has a larger diameter at 949 miles around; it’s perspective that makes them seem the same size. The image was originally taken by Cassini back on July 27, 2010, and has just now been released.
Those unfamiliar with the moons of Saturn may not know that Rhea is the second largest moon the planet has. Dione is the fourth largest moon of Saturn. The largest satellite orbiting Saturn is the aptly named Titan. Dione is a subject of interest for scientists; they believe it may have a subsurface ocean of liquid water.
Another interesting Dione tidbit is that it has more craters on the side facing away from the motion of it through space which isn’t consistent with where the craters should be. More impacts would hit the face of the moon traveling forward through space. Scientists explain this by theorizing that the moon must have been hit at some point by an impact significant enough to spin it 180-degrees on its axis.