A Grand Finale at Saturn for Cassini

Computer generated photograph from the NASA at Saturn series

Jessica Clot, BURSTOUT CONTRIBUTOR

English and Drama Graduate from Queen Mary.

Full Bio

Jessica is a graduate from Queen Mary, University of London. She has a passion for theatre and drama, and often wrote for CUB magazine, the university's official arts and culture magazine.

Imagine buying a car, running it for 3 billion miles over 20 years, taking pictures of nearly everything you see on route without a single fuel stop or mechanic and then driving it into a wall at 70,000 mph. That is exactly what the collaboration of the US National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Italian Space Agency have just done with the Cassini space probe.

Two decades of exploration to some of the most wondrous sites in the solar system ended in a Grand Finale on the 15 September 2017. Cassini, with its small Huygens piggy backed probe, is undoubtedly one of the most remarkable unmanned spacecraft ever built.

Launched on 15 October 1997, from Cape Canaveral Air Force Station in the USA, on a seven-year journey to reach Saturn, it flew twice past Venus, then past Earth and Jupiter to arrive safely in 2004. Now the real work started with its initial planned 4-year mission to explore the Saturnian system. In 2008, the spacecraft was in such good shape that the mission was extended to 2010 and then again, all the way to the Grand Finale.

Saturn is the most spectacular planet with its signature rings but two of its moons, Titan and Enceladus, turned out to be truly stunning. The rings were first proposed to exist by Dutch astronomer Christiaan Huygens in 1655 as a possible cause for the shadows seen on Saturn. His telescopes had greater power than the ones Galileo made and as a result, was also able to discover Titan in the same year. In 1675, an Italian-French astronomer, Giovanni Cassini, noticed a space inside the rings which is still known as the Cassini Division, hence the name of the main spacecraft sent to explore them.

The initial highlight of the mission was the deployment of the small Huygens probe, which landed on Saturn’s largest moon Titan. Titian is 50% larger than the Earth's Moon, and is 80% heavier. As the probe penetrated the thick atmosphere, data was relayed back to Earth by Cassini, showing Earth like terrain, with lakes and rain. However, the catch is this, for the existence of life on Titan, the rain is methane and the average daily temperature is around -179˚C! So, where next?

This Cassini image from 2012 shows Titan and its host planet Saturn.  Image credit: NASA/JPL-Caltech

It was detection by Cassini’s magnetometer regarding the small moon Enceladus and its apparent distortion of Saturn’s magnetic field that prompted a new mission objective - to fly by this small 300-mile-wide moon. It has the most reflective surface of any object in the solar system, but who could have imagined what Enceladus could harbour. Enceladus was not some inert small lump of rock!

This view of Saturn's moon Enceladus was taken by NASA's Cassini spacecraft. On October 28, 2015, Cassini made its closest pass directly through the icy plume jetting out of the moon's south pole. Image credit: NASA/JPL-Caltech

Beneath its crust hid a global ocean of liquid salty water and organic chemicals feeding 800 miles per hour geysers on its surface. Some liquid escapes to space or to one of Saturn’s many rings whilst the rest falls back as snow. If something this small could potentially show how life could have originated in the solar system, then the possibilities for other life in the universe, significantly increases. As Linda Spiker, Cassini Project Scientist claimed on the NASA website, ‘Enceladus discoveries have changed the direction of planetary science’.

After 20 years, Cassini’s fuel was running low and to avoid contaminating any moons’ surface, the Grand Finale was organised as a controlled crash into Saturn’s atmosphere. The last accomplishment was to dive between the rings and the planet’s surface, not once but 22 times. The end finally arrived as the intense heat of entry into Saturn’s atmosphere harmlessly evaporated the spacecraft as the last signal was sent.

This extraordinary mission demonstrated how if we really must, we can build things that have longevity and flexibility. For Cassini, it has left a scientific legacy for our desire to continue in learning more of how we came to be here, but still leaves the mystery as to why my car only has a 5-year warranty!