Cassini, one of Nasa’s most important spacecrafts, has crashed into Saturn and been destroyed.

The agency sent the craft to burn up on the planet’s surface to stop it spreading alien bacteria carried there from Earth. To avoid that, Cassini fell into Saturn’s atmosphere and burnt up like a meteor, spreading itself across the planet it has been exploring since it set off from Earth in 1997.

Cassini was actually destroyed more than an hour before the last signal reached Earth, but the messages take so much time to spread across the solar system that Nasa only just saw the signal drop off. When it did, the radio waves that engineers were watching live dropped off, as the equipment required to send them back to Earth burnt up.

Cassini's mission to Saturn Show all 9 1 /9 Cassini's mission to Saturn Cassini's mission to Saturn In this handout image released on April 30, 2013 by NASA, the spinning vortex of Saturn's north polar storm is seen from NASA's Cassini spacecraft on November 27, 2012 in the Saturnian system of space. The false-color image of the storm resembles a red rose surrounded by green foliage which was made by using a combination of spectral filters sensitive to wavelengths of near-infrared light at a distance of approximately 261,000 miles from Saturn NASA via Getty Images Cassini's mission to Saturn The planet Saturn is seen in the first color composite made of images taken by NASA's Cassini spacecraft on its approach to the ringed planet, October 21, 2002. The probe's arrival is still 20 months away. The planet was 285 million kilometers (177 million miles) away from the spacecraft, nearly twice the distance between the Sun and Earth, when Cassini took images of it using various filters NASA/Getty Images Cassini's mission to Saturn Nasa's Cassini spacecraft is shown diving through the plume of Saturn's moon Enceladus in 2015 Nasa/JPL-Caltech/Reuters Cassini's mission to Saturn NASA's Cassini spacecraft captured this view of planet Earth as a point of light between the icy rings of Saturn NASA/JPL-Caltech/Space Science Institute Cassini's mission to Saturn The giant plumes of ice on Enceladus seen by the Cassini spacecraft in 2009 Nasa Cassini's mission to Saturn The image of Titan is actually a composite of a number of pictures taken by Cassini during the flyby Cassini's mission to Saturn The unique six-sided jet stream at Saturn's north pole known as "the hexagon" taken by NASA's Cassini mission is seen in this still handout image from a movie released December 4, 2013. The movie, made from images obtained by Cassini's imaging cameras, is the first to show the hexagon in color filters, and the first movie to show a complete view from the north pole down to about 70 degrees north latitude. REUTERS/NASA/JPL-Caltech/SSI/Hampton/Handout (OUTER SPACE - Tags: SCIENCE TECHNOLOGY) THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS - RTX163SO REUTERS/NASA/JPL-Caltech/SSI/Hampton/Handout Cassini's mission to Saturn REUTERS/NASA/JPL-Caltech/Space Science Institute/Handout Cassini's mission to Saturn A handout photograph shows the first flash of sunlight reflected off a lake on Saturn's moon Titan taken by NASA's Cassini spacecraft on July 8, 2009 and released by NASA to Reuters December 17, 2009. The glint off a mirror-like surface is known as a specular reflection. It confirmed the presence of liquid in the moon's northern hemisphere, where lakes are more numerous and larger than those in the southern hemisphere. REUTERS/NASA/JPL/University of Arizona/DLR/Handout (UNITED STATES - Tags: SCI TECH IMAGES OF THE DAY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS - RTXRYK8 REUTERS/NASA/JPL/University of Arizona/DLR/Handout

“The signal from the spacecraft has gone, and within 45 seconds so will the spacecraft,” the project manager of the Cassini mission said. ”I hope you’re all as deeply proud fo this amazing accomplishment. Congratulations to you all. This has been an incredible mission, an incredible spacecraft, and you’ve all been an incredible team.”

The engineers working in Nasa’s control centre then applauded.

The destruction of the craft went entirely to plan, Nasa said. It had been forced to send it to Saturn where it would burn up and avoid accidentally landing on another moon – like Titan or Enceladus – which it might accidentally end up populating with aliens.

Scientists have described the loss of the craft with a mix of pride and sadness. It managed to learn much more than was expected, but researchers describe the sadness of losing the craft and so receiving no more information from it.

What did the spacecraft Cassini achieve?

But work will continue using all the data that has already been transmitted back from the craft. That includes the pictures it sent right up until the end, taking last photos of the system over Thursday and then sending back samples of Saturn’s atmosphere at the same time as it was being destroyed by it.