After 13 years in orbit, Nasa’s Cassini spacecraft will begin shifting its orbit Saturday, before it descends between Saturn and its rings. It will be the first craft to travel between the planet and its innermost ring, traversing that space roughly once a week before a planned crash into Saturn’s atmosphere on September 15th. The summer will see a kind of grand finale, concluding Cassini’s 13 years of exploration.

Cassini arrived at Saturn in 2004, after its 1997 launch. It has traveled about 4 billion space miles, exploring Saturn’s many moons. The craft is credited with investigating a number of notable phenomenon on Saturn and its moons, including a six-sided storm at the planet’s north pole and the threads of dust, rocks, and ice that make up the planet’s famous rings.

Thanks to Cassini’s journey, Nasa now knows that Saturn’s moon Enceladus is an “ocean world” made up mostly of water, with plumes of salty water emerging from cracks in the moon’s icy surface. Cassini’s examination of the plumes detected hydrogen, which suggests the presence of hydrothermal activity – heat and energy at the ocean floor that could provide the building blocks of microbial life.

Next, Nasa scientists hope to fly a probe through the plumes, capable of detecting microbes. Unlike similar prospective projects to detect life on Europa, a moon of Jupiter, a probe to Enceladus would not need to land and drill to detect life.

Cassini also explored Titan, the only moon in the solar system with an atmosphere thicker than that of Earth. The craft’s Huygens probe landed on Titan, discovering a frozen landscape, with dunes of methane and riverbeds. The probes radar also found oily lakes made up of methane and ethane. The discoveries have fueled speculation on what kind of life could exist in that kind of chemical landscape, and Nasa scientists hope to someday send a boat capable of sailing the methane seas on Titan.

Part of the thinking behind Cassini’s dramatic finish, incinerating in Saturn’s atmosphere, is to make sure any microbes from Earth possibly still carried by the craft do not contaminate any budding microbial environments that may have yet to be discovered.

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