NASA's Cassini to crash into Saturn today, ending 20 years of mission

Richard Wilson

With the spacecraft's fuel spent, operators deliberately plunged Cassini into Saturn-which it had orbited for 13 years -to make sure the planet's moons remain pristine for future exploration.

The spacecraft's fateful dive is the final beat in the mission's Grand Finale, 22 weekly dives, which began in late April, through the gap between Saturn and its rings. For the first time in its mission, the spacecraft flew between the planet and the rings. Over the mission, the northern hemisphere shifted from a bluish hue to the more familiar golden tones as the shadows cast by Saturn's rings moved south.

The "grand finale" to the Cassini mission marks the end to one of the most successful planetary space missions in history.

Linda Spilker, Cassini project scientist, likened Cassini's mission to a marathon.

No spacecraft has ever ventured so close to the planet before, NASA said. NASA officials expect that Cassini broke apart about 45 seconds after that final transmission, due to the intense friction and heat generated by the fall.

Cassini was on a four-year mission to explore Saturn, its atmosphere, magnetosphere, rings, and to study Saturn's moons, especially Titan, the only moon in the Solar System to have a substantial atmosphere.

Contact was lost with the Cassini spacecraft a minute after it reached an altitude of about 1,500 kilometres above the planets estimated cloud tops. Cassini has filled in numerous details, giving us an unparalleled look. As the probe descended through Titan's atmosphere, it discovered liquid methane lakes and river channels draining into a methane sea. But then Cassini caught some shots of geyser plumes in glowing silhouette against the moon's edge. Titan is our solar system's second-biggest moon, after Jupiter's Ganymede, and the only one with a proper, if forbidding, atmosphere, which is nearly all nitrogen, like Earth's before things got interesting.

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The Cassini mission also had a role in promoting collaboration between countries, different generations of scientists and across political boundaries. The space probe of his namesake, on the other hand, before it goes out, will send a final echo which will radiate across the solar system for hours and the signals will travel through the cosmos for eternity. That's when radio signals from the spacecraft - its last scientific gifts to Earth - came to an abrupt halt.

Enceladus, February 2016. With a vast underground ocean that explodes into gas through gashes in the surface, this handsome moon is one of the better bets for extraterrestrial life in our solar system.

On this trajectory, Cassini would sail too close to Saturn to survive.

Cassini has also found evidence of an underground ocean on Saturn's sixth largest moon - Enceladus.

Goodnight, so long, and thanks for filling us with wonder, Cassini. Scientists still need to decode the last bits of data the vehicle gathered during its plunge, as well as all of the information the probe has received during its journey at Saturn.

The concern was that the spacecraft, if left to drift in orbit around the planet, could one day collide with the moons Enceladus or Titan, two worlds that scientists - using data from Cassini itself - believe to be potentially habitable. But Cassini went off relatively without a hitch, and even beamed back a few "pale blue dot" pictures of a tiny Earth nestled between the massive rings of Saturn.



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