April 15, 2024

I, Science

The science magazine of Imperial College

In our final article of the Cassini series, we take a look at The Grand Finale mission - a daring set of manoeuvres through Saturn's rings that will end in the destruction of the spacecraft this Friday.

As the Cassini mission enters its final days, it gets ready to complete its last missions, aptly titled “The Grand Finale”, that will consist of a series of passes between Saturn and Saturn’s rings, before crashing in to Saturn’s atmosphere.

The Grand Finale will acquire information about the composition, temperature profile and structure of a portion of Saturn’s rings that are close to it’s surface. In order to achieve this, Cassini will carry out a series of daring dives around and through the rings – manoeuvres that have never been attempted before.

In 1610, Galileo Galilei discovered Saturn, naming it’s curious rings “ears”. Saturn’s majestic rings are perhaps one of the most iconic and recognisable space images. It is not known exactly how Saturn’s rings formed, but there are two leading theories. The first is that they were created some time after Saturn had formed, when a satellite got too close to the planet and was ripped apart by gravity, eventually forming regular ring systems due to the planet’s gravity and rotation. The other theory is that the rings were formed from the same nebular material that created Saturn.

Up until the Cassini mission, the structure of the rings had still largely remained a mystery to us, but since reaching Saturn’s system in 2004, Cassini has been sending back breathtaking images of our distant neighbour and it’s rings, providing us with high-resolution insights in to its secrets.

moon of saturn embedded in rings

Daphnis, one of Saturn’s moons embedded in its rings, creates waves in the surrounding material as it orbits within the Keeler gap, NASA

3 moons of Saturn outside of rings

Three of Saturn’s moons, Tethys, Enceladus and Mimas, were captured by Cassini in this group photo, NASA

shadow of saturn on its rings

In this image, Saturn’s shadow is projected on to its rings, NASA

Through analysing the many images sent back by Cassini, scientists have now been able to ascertain with certainty that the rings of Saturn are composed of rock and ice that vary in size; ranging from material as large as buildings to those as small as a grain of sand.

In the Grand Finale, Cassini will gradually dive through the region between the Saturn and its rings. It is expected that this will provide scientists with new insights about the rings, such as enabling a more precise determination of their origin, and revealing their composition, temperature profile and structure. However, the manoeuvre’s are complicated and risky and to avoid damage from the rock and ice, Cassini’s will call upon it’s high-gain antenna to help it meticulously adjust its direction as it travels down towards the atmosphere of Saturn for it’s last few flybys.

Cassini’s 20-year mission has provided us with unprecedented information about Saturn and its system. In what is perhaps one of it’s most memorable feats, it carried the Huygens probe, bound for the surface of Titan. The probe detached from Cassini on December 2004, and landed on the surface of Titan on January 14 2005, returning not only images of its surface, but also the sound clip recorded as Huygens rushed through Titan’s atmosphere, for the first time enabling the weather of another planet to be heard by humans.

It has returned data on Jupiter and its moons, performed a close flyby of an asteroid, and even enabled scientists to better test Einstein’s theory of General Relativity.

There is no doubt that the Cassini mission will be missed, but its success has paved the way for the continued exploration of our universe. So we wish the spacecraft luck as it transmits its last lots of data back to Earth, and gets ready to spend it’s retirement on Saturn.

Sichao Liu, Xin Yan, Xuewei Zhang, Napat Kittiwongsophon – Centre for Academic English, Imperial College London

Banner image: Saturn backlit by the Sun, NASA