NASA’s Cassini spacecraft has been voyaging through the solar system since October 1997. It went into orbit around Saturn in 2004 and has since taken thousands of images of the planet, its rings, and its many diverse moons. But on 15 September, the craft will end its mission by crashing into Saturn.
As the Cassini mission draws to an end, New Scientist looks back at some of the most impressive images that the spacecraft has sent back to Earth.
Saturn approaching its northern summer
Taken in April 2016, this set of stitched-together images reveals the beginning of the summer solstice in Saturn’s northern hemisphere. Increased sunlight causes rising hazes that blur some of the planet’s swirling features and mute the bluish hues more visible in the northern winter.
Cassini marked scientists’ first opportunity to study the temperature and composition of Saturn’s rings from an orbit around the planet. The rings are only about 10 metres thick and made mostly of ice chunks ranging in size from microns to metres across. This image was taken from about 1.2 million kilometres beyond Saturn’s surface.
Enceladus and its geysers
Before we sent Cassini on a path past Enceladus, scientists expected Saturn’s sixth-largest moon to be frozen solid. But these geysers spewing from its south pole indicate a buried sea that could span the whole moon. Later on, Cassini sailed through the jets and found that they contain nearly all the required ingredients for life, making Enceladus’s subsurface ocean a strong contender for potential life in our solar system.
Saturn’s largest moon, Titan, also has serious potential for hosting microscopic life. Although visible light cannot peer through this moon’s thick, hazy atmosphere, infrared observations like the one seen here reveal its liquid methane seas. Titan is freezing cold and has no liquid water, but Cassini has seen some promising signs for the possibility of life there.
Saturn’s polar hexagon
Saturn’s North Pole hosts an enormous spinning hexagon almost 25,000 kilometres wide. Its constant churning is generated by a powerful wind current that makes the hexagon rotate once every 10 and a half hours around the huge storm at its centre.
In this false-colour image of the eye of Saturn’s north polar vortex, red indicates low clouds and green high ones. This colossal hurricane, about 4000 kilometres across, whirls at Saturn’s north pole year-round, but nobody knows what keeps it spinning.
Daphnis makes waves
Saturn’s moon Daphnis is only 8 kilometres across, but can still make waves. As Daphnis orbits, its gravity causes ripples in the rings. Some particles from the rings also stick to the miniature moon, building up a ridge around its equator – a process that happens on several of the moons that surf the planet’s rings.
Titan, Dione, and Saturn’s rings
Saturn has 62 confirmed moons. Two of them, Titan and Dione, pose here against a backdrop of the planet’s rings. Titan’s thick orange smog makes it the only known moon with a significant atmosphere. Most of Dione is water ice, but Cassini detected hints that it may conceal a liquid water ocean.
In July 2013, Cassini flew into the shadow of Saturn, pointed its cameras back at the planet, and took a series of images with the sun’s light filtering through the gaps in the rings. This mosaic uses 141 of those pictures.
Earth from Saturn
As Carl Sagan wrote, “That’s here. That’s home. That’s us.” The pale blue dot floating under Saturn’s rings is Earth from 1.44 billion kilometers away. With no more spacecraft exploring the outer solar system, it’s not a view we’ll see again soon.