Notes
There are four planets in our solar system with rings: Saturn, Neptune, Jupiter, and Uranus. All of these planets are gas giants. From www.universetoday.com: "A gas giant [is] a planet that is not composed of mostly rock and other solid substances. Gas giants are almost entirely formed of various gases. These planets are not completely gas though. At the center, is what astronomers call a rocky center. This term is somewhat misleading though because the rocky center is actually liquid compounds, including molten heavy metals. The term was created by James Blish, a science fiction writer from the mid-1900′s. Gas giants are also called Jovian planets after Jupiter, the prototype of gas giants in our Solar System. There are four gas giants in our Solar System – Jupiter, Saturn, Uranus, and Neptune.
"The gas giants in our Solar Systems have a number of similar characteristics. All of our Solar System’s gas giants are outer planets, which means they are the furthest planets from the Sun. Compared to terrestrial planets, gas giants are extremely large and massive. For example, Jupiter has a mass 318 times the mass of Earth, which is a terrestrial planet. Despite their size, gas giants are low-density planets because they are composed almost entirely of gas. In addition to being large, these planets rotate extremely quickly. Jupiter rotates so quickly that it has actually flattened at its poles. The gas giants are extremely cold planets, although that is mostly due to the fact that they are very far from the Sun. Gas giants also have dozens of satellites and ring systems. Saturn is famous for its beautiful rings, which can be seen with the unaided eye from Earth."
The planet Saturn with its rings.
Image from google images.
Mars is a terrestrial planet and does not have rings.
The planet Mars.
Image from google images.
The rings of Neptune, Jupiter, and Uranus were discovered relatively recently. In 1921, Saturn was the only planet known to have rings. It is likely that Mary incorrectly remembered the name of the planet depicted with rings.