NASA is now receiving the last photos ever taken by the Cassini probe at Saturn

NASA has begun to receive the last photos ever taken by its doomed Cassini probe at Saturn, and will soon upload them to its public servers.

Cassini — a bus-size, nuclear-powered robot — launched toward the planet in 1997. It took seven years to reach Saturn and, since the probe's arrival, it has recorded more than 450,000 pictures.

However, Cassini has run low on propellant, and will become an artificial meteor at Saturn on Friday morning as it plunges to its death.

If NASA had risked letting the propellant tanks run dry, it would have lost control of the $3.26-billion mission, leaving open a slim but significant 1-in-a-million chance (over the next 50 years) that Cassini would crash into and contaminate Enceladus: an icy moon of Saturn that hides a salty ocean and possibly alien life. Titan, the planet's largest moon, may also have a habitable ocean.

18 PHOTOS
Cassini's best photos through the years
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Cassini's best photos through the years
IN SPACE - AUGUST 18: In this handout image provided by the National Aeronautics and Space Administration (NASA), looking toward the sunlit side of the rings, Saturn's rings and the icy moon Enceladus are seen in visible light with the Cassini spacecraft wide-angle camera on Aug. 18, 2015. Saturn's night side (top C), is illuminated by sunlight reflected off the rings. The view was acquired at a distance of approximately 87,000 miles from Enceladus. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - NOVEMBER 19: In this handout image provided by the National Aeronautics and Space Administration (NASA), the planet Saturn's 'Death Star' moon Mimas is shown from a distance of approximately 28,000 miles (45,000 kilometers), taken by NASA's spacecraft Cassini-Huygens in its closest approach to the pock-marked moon on January 30, 2017. The lighting, reflected from Saturn, has been enhanced by NASA. Cassini is nearing the end of its nearly 20-year mission. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - JANUARY 18: In this handout image provided by the National Aeronautics and Space Administration (NASA), Saturn's sunlit face is visible in this view from the vantage point just beneath the unilluminated side beneath the ring plane and taken in green light with the Cassini spacecraft wide-angle camera on Jan. 18, 2017. The view was acquired at a distance of approximately 630,000 miles from Saturn. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - JANUARY 16: In this handout image provided by the National Aeronautics and Space Administration (NASA), the wavemaker moon, Daphnis, is featured in this view, taken as NASA's Cassini spacecraft made one of its ring-grazing passes over the outer edges of Saturn's rings on Jan. 16, 2017. Daphnis (5 miles across) orbits within the 26-mile wide Keeler Gap. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - DECEMBER 18: In this handout image provided by the National Aeronautics and Space Administration (NASA), the image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 18, 2016. The image features a density wave in Saturn's A ring (at left) that lies around 134,500 km from Saturn. The view was obtained at a distance of approximately 34,000 miles (56,000 kilometers) from the rings and looks toward the unilluminated side of the rings. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - DECEMBER 2: In this handout image provided by the National Aeronautics and Space Administration (NASA), the image of Saturn's atmosphere was taken with the Cassini spacecraft wide-angle camera on Dec. 2, 2016 The view was acquired at a distance of approximately 592,000 miles (953,000 kilometers) from Saturn. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - APRIL 8: In this handout image provided by the National Aeronautics and Space Administration (NASA), this view looks toward the sunlit side of the rings shows a bright disruption in Saturn's narrow F ring from about 15 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 8, 2016. The view was acquired at a distance of approximately 1.4 million miles from Saturn. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
The Galilean satellite Io floats above the cloudtops of Jupiter in this image captured on January 1, 2001. Cassini Spacecraft. (Photo by: Photo12/UIG via Getty Images)
From on high, the Cassini spacecraft spies a group of three ring moons in their travels around Saturn. (Photo by: Photo12/UIG via Getty Images)
IN SPACE - JANUARY 28: In this handout image provided by the National Aeronautics and Space Administration (NASA), this view looks toward the sunlit side of the rings and was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 28, 2016. The 2,980-mile-wide division in Saturn's rings (seen between the bright B ring and dimmer A ring) was acquired at a distance of approximately 740,000 miles (1.2 million kilometers) from Saturn. Between April and September 2017, Cassini will plunge repeatedly through the gap that separates the planet from the rings. The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. (Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images)
IN SPACE - JULY 19: In this handout from NASA, the planet Saturn is seen backlit by the sun, sent Cassini spacecraft July 19, 2013 in space. NASA unvieled the image, that spans 404,880 miles (651,591 kilometers) across, November 12, 2013. Besides the rings, three planets, Mars, Venus and Earth, are visible in the image. (Photo by NASA/JPL-Caltech/SSI via Getty Images)
In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its moon in the same frame. It is only one footprint in a mosaic of 33 footprints covering the entire Saturn ring system (including Saturn itself). At each footprint, images were taken in different spectral filters for a total of 323 images: some were taken for scientific purposes and some to produce a natural color mosaic. This is the only wide-angle footprint that has the Earth-moon system in it. (Photo by NASA/Handout/Corbis via Getty Images)
This true-color simulated view of Jupiter is composed of 4 images taken by NASA's Cassini spacecraft on December 7, 2000. (Photo by: Universal History Archive/UIG via Getty Images)
Shadows cast by Saturn's rings darken the southern hemisphere of the planet and give a truncated appearance to the bottom of this Cassini spacecraft image. (Photo by: Universal History Archive/UIG via Getty Images)
Sunlight scattering through the periphery of Titan's atmosphere reaches Cassini as the spacecraft's camera is pointed at the dark side of the moon. (Photo by: Universal History Archive/UIG via Getty Images)
Rhea's trailing hemisphere shows off its wispy terrain on the left of this image which includes Saturn's rings in the distance. Cassini. (Photo by: Universal History Archive/UIG via Getty Images)
Saturn's small moon Prometheus. Cassini. (Photo by: Universal History Archive/UIG via Getty Images)
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"Because of planetary protection, and our desire to go back to Enceladus, and go back to Titan ... we must protect those bodies for future exploration," Jim Green, the leader of NASA's planetary science program, told reporters on Wednesday.

This led NASA to plan Cassini's "Grand Finale": a series of 22 dives between the planet and its rings, with one final orbit to destroy the probe on Friday.

Cassini snapped its final of many images at Saturn on Thursday around 3:58 p.m. EDT. It took more than an hour for NASA to start receiving those photos, however, because it takes light (and the probe's data signal) more than an hour to reach Earth from Saturn.

That data began trickling in on Thursday around 5:45 p.m. EDT, according to the Deep Space Network. Fully transmitting all of the photos should take about 11 hours, Earl Maize, an engineer at NASA's Jet Propulsion Laboratory (JPL) who manages the Cassini mission, told reporters on Wednesday.

"We'll be able to share those with you sometime Friday morning," Maize said.

Alan Byers, a spokesperson for NASA JPL, told Business Insider that the first images should be posted to Cassini's raw image gallery starting around 11 p.m. EDT.

What Cassini's final images will show

Cassini was speeding toward Saturn's atmosphere, about to take its 78,000-mph plunge, when it took its final pictures.

Linda Spilker, a Cassini project scientist and a planetary scientist at NASA JPL, walked reporters through all of those last planned images on Wednesday.

"In that last period of time, looking around Saturn, what we're doing is taking our final picture postcards of the Saturn system, looking at our favorite targets to put these images into our Cassini scrapbook," Spilker said.

From a distance, the probe will take multiple photos of Saturn and its rings in color — "basically our last look at the entire system," she said.

There will be photos of Enceladus setting across the northern limb of Saturn. Titan — which has liquid-hydrocarbon lakes, an atmosphere twice as thick as Earth's, and seasonal rain — also got some attention.

"We're going to take some goodbye pictures of Titan, a last look to see if there's any weather or clouds going on," she Spilker said.

NASA will also show images of Cassini's last close-up look at Saturn's rings.

One focus was "Peggy," a group of particles that "might break free to become a moon," she said, as well as propeller objects that are "trying to open up gaps in Saturn's rings, but are not quite big enough to do that."

The final images to trickle onto NASA's servers will show the spot on Saturn's dark side toward which Cassini will dive — "Cassini's final home inside the planet Saturn itself," Spilker said.

Cassini is scheduled to disintegrate starting around 6:22 a.m. EDT on Friday, though it will take until 7:55 a.m. EDT for NASA to receive the probe's last packet of data.

While it's unlikely that any telescope will see the probe die, you can tune in to NASA TV's live broadcast of mission control below.

The space agency's coverage will start around 7 a.m. EDT.

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