“After two decades in space, NASA’s Cassini spacecraft has ended its remarkable journey of exploration. Having expended almost every bit of the rocket propellant it carried to Saturn, operators deliberately plunged Cassini into the planet to ensure Saturn’s moons remain pristine for future exploration—in particular, the ice-covered, ocean-bearing moon Enceladus, but also Titan, with its intriguing pre-biotic chemistry. Read more Cassini mission ›