The space probe Cassini went on a 20-year voyage to study Saturn's secrets and as a result, our knowledge has grown, well, astronomic

ally, one might say. Here is some of what we learned.

History of Observation

Six planets were known to the ancients, Mercury, Venus, Mars, Jupiter, Saturn and, of course Earth, however, any knowledge about them was limited to what was evident to the unaided eye. During the Renaissance, Copernicus outlined the specific arrangement of the planets as well as the facts they each orbited around our sun rather than around the Earth. It wasn't until Galileo's telescope that we were able to begin looking at the surfaces of the planets to learn about them in any detail.

When Galileo first observed Saturn's rings in 1610, he thought he was looking at moons and was astounded when, several years later while studying the planet, he saw that the "moons" had disappeared. In fact, he was seeing Saturn that night with the rings "on edge" such that they could not be seen against the backdrop of that huge, gaseous planet. Forty-five years later, Dutch astronomer Christiaan Huygens was able to discern that what Galileo had seen were rings around the planet.

Space probes became the next avenue of discovery beginning in 1979 and culminating with the Cassini-Huygens spacecraft 20-year mission which ended in 2017. 

What Cassini Taught Us About Saturn

Cassini sent us a lot of new information. Here are a few things we now know about the planet, its rings and its moons that we didn't know before.

We did know that Saturn had a lot of moons, but Cassini was able to find 6 additional ones bringing the total new known total to 62.  Cassini also helped us solve a 300 year old mystery about the moon Iapetus, which appears light on one side and dark on the other. Scientists weren't sure of the reason for this but now know that the dark side is covered in a reddish dust and the light side is covered in frost.  In 2005, Cassini sent a probe named Huygens to Saturn's largest moon, Titan. The Huygens probe made a successful landing, took soil samples and sent photographs back to Earth. We believe its hills are mainly composed of water ice and, with methane clouds, its atmosphere seems to resemble the primordial conditions of Earth's. Huygens' mission represents the most distant landing of any man-made craft to date. It also appears that life as we know it might be able to exist on the moon Enceladus which has salty water under its surface.

Saturn is the only known planet other than Earth that produces lightening. We received photos and even a video of this lightening from Cassini in 2009.

Cassini picked up some type of natural radio waves emanating from inside the planet. Further information on this will have to wait for future exploration.

For the first time, we were able to study the size, temperature, composition and distribution of Saturn’s rings up close from within Saturn orbit. According to NASA, some of the key things we learned are as follows.

◆ The particles that make up Saturn’s rings range in size from smaller than a grain of sand to as large as mountains.
◆ Cassini found that water jets from the moon Enceladus provide much of the material in Saturn’s more diffuse ring known as the E-ring.
◆ Cassini studied features in Saturn’s rings called “spokes,” which can be longer than the diameter of Earth. Scientists think they’re made of tiny icy particles that are lifted by an electrostatic charge and only last a few hours.
◆ During Saturn's equinox, when the rings face the sun edge-on, Cassini watched ring particles produce elongated shadows that revealed unexpectedly immense ring chunks that measured miles (kilometers) in size. Although 3 other planets in our solar system have rings, none compare with the beauty and intensity of Saturn's. There is undoubtedly much more to learn about our 6th planet. Cassini gave us a huge jump into that future.