For many of us who have been switching between different schools, even different cities for most of our life, it can be hard to visualise doing one thing for 20 years. Many undergraduates have not yet celebrated their 20th birthday. But for the past twenty years, the Cassini mission has been traveling through space with one goal: to study the world of Saturn.
It all started on October 15, 1997 when the Cassini-Huygens probe was launched from Cape Canaveral, Florida. The next seven years were spent traveling through space and using the gravity from Venus, Earth, and Jupiter to propel the probe all the way to Saturn’s orbit.
Shortly after it arrived, the Huygens probe separated from Cassini and dropped though the atmosphere of Saturn’s largest moon, Titan, and became the first probe to land on a moon other than our own. From this probe, we have learned that Titan has rain, lakes, and oceans beneath a thick Nitrogen-rich atmosphere. It’s not liquid water, but liquid ethane and methane are similarly awesome finds.
In the next thirteen years exploring the Saturn system, Cassini learned many more incredible things. I’d like to highlight three accomplishments in particular.
The rings of Saturn are the shiny glory of our Solar System, but until Cassini we did not really understand them. Images from Cassini revealed that the rings change and are relatively young, only 100 million years old, so we are lucky to witness them. The rings are confirmed to be of irregular thickness as well. Taking advantage of a rare alignment between the sun and the rings, Cassini was able to photograph structures on the rings of Saturn and measure their heights, some nearly 1.5 miles high, based on the shadows they projected on the interior of the rings. The rings also provide clues for how planets may form around stars. Just as planets form from a disc of gas and dust orbiting a star, Cassini witnessed the possible birth of a new moon within the rings.
Looking at the planet itself, Cassini discovered a large storm at the North pole of Saturn. This storm rages year round, not unlike Jupiter’s famous red spot. However, this storm is a hexagon shape. As if that wasn’t mysterious enough, the storm also changes colors. Images from June 2013 show the storm to be entirely blue, while images taken in April of 2017 show only a small blue center and the rest is a hazy yellow. Scientists are still hypothesizing about what causes the hexagonal shape and the color differences; this will be one of the many mysteries that astronomers hope to unravel in the many months of deciphering the large quantities of data received from Cassini.
The final accomplishment is not as scientific as the others, but it embodies our spirit of curiosity, discovery, and childlike wonder as a human race. On July 19th, 2013 from 5:27 to 5:42 pm EDT, NASA encouraged the world to take a moment to walk outside, look up at the sky, and wave to Cassini as the spacecraft turned back to take a picture of our home planet beneath the rings of Saturn. This is the first time that the public knew their picture was going to be taken from beyond our atmosphere and encouraged to ‘say cheese’. A total of 323 images were taken to create a mosaic spanning 404,880 miles across. The previous picture taken of Earth from the outer solar system dates back to 1990 by Voyager 1 and it is still as breathtaking.
Cassini’s mission ended on September 15th, 2017 at 7:55:46 am ET. It has been a magnificent mission and although the spacecraft has been safely crushed by the atmosphere of Saturn, the science still continues. Raw data can only give us so much, but we have many months of thrilling science and new discoveries to look forward to, as more detailed analyses can be done on the raw data. The science done by Cassini will change astronomy textbooks and will be remembered by many generations to come.