The following is an excerpt from our printed article on the Cassini mission. To read the entire feature check out issue 5 of All About Space, on sale at the Imagine Shop from 18 October.
Our knowledge of Saturn’s system today is far greater than it has ever been. We know that the planet itself has some extreme weather at its poles, we know how fast it rotates, and we know the characteristics of its atmosphere. We also know a lot about its moons, from the wet and wonderful world of Titan to the mysterious Iapetus with its giant equatorial ridge. However, were it not for the Cassini-Huygens mission, much of our knowledge of the Saturnian system would remain hidden away.
Launched 15 years ago on 18 October 1997, the Cassini-Huygens spacecraft (to use its full name, although only the Cassini orbiter is still operative after the Huygens probe landed on Titan in January 2005) has greatly increased our understanding of Saturn, and in some parts Jupiter, and its surrounding moons. It was, and is, a mission jointly operated by NASA, the ESA and ASI (Italian Space Agency) to further our understanding of Saturn and its surrounding system like never before. While its seven-year journey to the second largest planet in our Solar System included flybys of Venus, the Moon and Jupiter, the crux of its mission has focused around Saturn, and after becoming the first spacecraft to orbit the planet in 2004 it continues to operate nominally, constantly returning startling new data and images.
The mission itself has been a resounding success and highlights the benefits of an international endeavour to explore space. “Cassini is one of the greatest unmanned missions to date,” said NASA JPL’s Cassini project scientist Dr. Linda Spilker to All About Space. “Cassini’s discoveries have implications not only for the Saturn system, but by extension for the other outer planets, and their icy moons and rings, as well as exoplanets orbiting other stars.”
Indeed, numerous findings by Cassini have helped markedly increase our understanding of water formation on other celestial bodies and, as Dr. Spilker says, the importance of finding ice on other worlds. “Cassini’s discoveries have expanded the envelope of potentially habitable zones in our Solar System with the discovery of a liquid water reservoir on Enceladus, and a liquid water ocean underneath Titan’s icy crust.”
Of all the observations Cassini has made in its mission so far, Dr. Spilker highlights the discovery of jets of water and icy particles on Enceladus as one of the most significant yet. “This unexpected discovery completely changed our thinking about activity on small bodies, as Enceladus is only 500km [310 miles] in diameter. A heat source and compounds that include carbon, hydrogen, oxygen and nitrogen in the liquid water reservoir underneath Enceladus’ south pole provide a potentially habitable environment far from the Sun.”
15 years and counting, no spacecraft has increased our understanding of the Solar System, particularly Saturn and its surrounding moons, like Cassini has, and it still has five more years to blow our minds again and again before the mission ends with a Saturn impact in 2017.