Contact has been lost with the Cassini spacecraft after it completed a "death dive" into the upper atmosphere of Saturn and transmitted its final signal, according to NASA. The spacecraft deliberately sank into Saturn's upper atmosphere at a high speed and plunged itself into the planet just after 6:30 a.m. ET Friday. Given the amount of time it takes signals to reach Earth, the final signal and last bits of data reached the Deep Space Network's Canberra Station in Australia about an hour and a half later. NASA confirmed the spacecraft's demise at 7:55 a.m. ET, as predicted.
For about a minute, Cassini was able to transmit new data about the planet's composition as long as its antenna remained pointed toward Earth, with the assist from small thrusters. Then, the spacecraft burned and disintegrated due to the heat and high pressure of the hostile atmosphere. It became part of the planet it set out to explore.
The final chapter in a remarkable mission of exploration and discovery, Cassini's Grand Finale is in many ways like a brand new mission. Twenty-two times, NASA's Cassini spacecraft will dive through the unexplored space between Saturn and its rings. What we learn from these ultra-close passes over the planet could be some of the most exciting revelations ever returned by the long-lived spacecraft. This animated video tells the story of Cassini's final, daring assignment and looks back at what the mission has accomplished.
On Thursday, Cassini took its last images and transmitted all the data on its recorder to prepare for the final plunge. The final data from Friday is already being processed and analyzed. For the team behind the mission, losing their spacecraft is bittersweet: Many are sad that the mission is over but excited to see the groundbreaking science provided by unprecedented proximity to Saturn during the final dive.
"The Cassini operations team did an absolutely stellar job guiding the spacecraft to its noble end," said Earl Maize, Cassini project manager. "From designing the trajectory seven years ago, to navigating through the 22 nail-biting plunges between Saturn and its rings, this is a crack shot group of scientists and engineers that scripted a fitting end to a great mission. What a way to go. Truly a blaze of glory."
The team members that have worked together from concept to the final minutes exchanged hugs and tears in Mission Control at NASA's Jet Propulsion Laboratory in California after the loss of signal was confirmed.
"Things never will be quite the same for those of us on the Cassini team now that the spacecraft is no longer flying," Spilker said. "But, we take comfort knowing that every time we look up at Saturn in the night sky, part of Cassini will be there, too."
After launching in 1997 and reaching the Saturn system in 2004, Cassini spent 13 years exploring the planet and its moons. The data and images led to numerous discoveries that changed how scientists think about our solar system.
"A superb machine in an amazing place doing everything possible to reveal the mysteries and secrets of our solar system," Maize said. "This morning, a lone explorer, a machine made by humankind, finished its mission 900 million miles away. To the very end, the spacecraft did everything we asked. We believe we got every last second of data. We have indeed accomplished everything we set out to do."
This illustration shows NASA’s Cassini spacecraft above Saturn's northern hemisphere prior to one of its 22 grand finale dives. NASA's Cassini spacecraft, in orbit around Saturn since 2004, is about to begin the final chapter of its remarkable story. On Wednesday, April 26, the spacecraft will make the first in a series of dives through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its rings as part of the mission’s grand finale.
Why the dramatic ending?
Cassini had its closest approach with Saturn's moon Titan on Monday, dubbed a "goodbye kiss" by the mission's engineers because it provided the gravity assist that sent the spacecraft on its final encounter with Saturn.
Mission scientists and operators gave Cassini this fiery send-off on purpose. Although many other options were considered - such as "parking" the spacecraft in orbit - they didn't want to risk Cassini colliding with any of Saturn's moons.
Cassini data and observations revealed that while seemingly inhospitable to us, the moons Enceladus and Titan could be habitable for some form of life. And NASA didn't want to risk contaminating the moons or any future studies of them with Earth particles. Although Cassini has been in space for 20 years, microbes from Earth could still exist on the spacecraft without air, water or protection from radiation.
Although the mission itself has ended, the data and observations provided by Cassini will provide new details about the planet, its unique rings and its moons for decades to come.
"Cassini may be gone, but its scientific bounty will keep us occupied for many years," Spilker said. "We've only scratched the surface of what we can learn from the mountain of data it has sent back over its lifetime."
During the final plunge, the Ion and Neutral Mass Spectrometer acted as the "nose" of the spacecraft, directly sampling the composition and structure of the atmosphere - something that can't be done from orbit, said Hunter Waite, team lead for the spectrometer.
This was in the hopes of investigating the "ring rain" phenomenon discovered by NASA's Voyager mission in the early 1980s, in which it appeared that the rings were raining down material on the planet and causing changes in the atmosphere. The spectrometer could determine what material is from the rings and what material is part of the atmosphere.
Cassini's grand finale actually began in April, with a series of dives between Saturn's rings, close to the planet and its moons, providing unprecedented insight. This is another reason the mission scientists decided on Cassini's particular end-game: The final dive was a dramatic conclusion to this long and scientifically valuable goodbye.
Illustration of NASA’s Cassini spacecraft during its final plunge into Saturn’s atmosphere on Sept. 15, 2017.
What Cassini taught us and what's next
Inspired to learn more after flybys of Saturn by NASA's Voyager missions, the Cassini mission was designed to be an international effort that united NASA, the European Space Agency and the Italian Space Agency.
It is known as the Cassini-Huygens mission because it delivered the European agency's Huygens probe to Titan, the "first descent and landing on a world in the outer solar system," according to NASA.
The Cassini mission has been extended twice and finally used up the last of its rocket propellant this week.
In the end, Cassini witnessed about half of a Saturn year. When the craft arrived, Saturn's northern hemisphere was emerging from winter. As seasons on Saturn last about seven Earth years each, Cassini was just able to witness summer in the northern hemisphere before the mission ended.
Over the years, Cassini has revealed insights about Saturn, its rings and how they operate, the complexities of its moons, the history of the solar system and planet formation and even the other places in our solar system where life might exist: ocean worlds. Cassini has collected more than 450,000 images using a visible light camera.
It has traveled nearly five billion miles, executed 2.5 million commands, conducted 162 targeted flybys of Saturn's moons, completed 294 orbits and its collected data has led to the publication of nearly 4,000 research papers.
When Cassini arrived, it witnessed a giant storm circling the planet for nine months. We learned that there are 3-D structures in the rings. Serendipitous observations showed that icy jets erupt from Enceladus. And Titan not only has seas and lakes of liquid ethane and methane, it has an atmosphere of chemicals that rain down, forming a unique chemistry that could lead to life.
"This is the final chapter of an amazing mission, but it's also a new beginning," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate. "Cassini's discovery of ocean worlds at Titan and Enceladus changed everything, shaking our views to the core about surprising places to search for potential life beyond Earth."
And the spacecraft itself, as well as its instruments, are informing future missions like NASA's Europa Clipper mission to explore Jupiter's icy moon, launching in the 2020s.
"Cassini has enabled those future missions to be possible," said Jim Green, NASA's director of planetary science.
NASA's New Frontiers competition has called for proposals that include future missions to the Saturn system. The proposals include a Saturn probe that explore the planet deeper than Cassini. Intrigued by Cassini's discoveries, scientists have submitted concepts for future "spacecraft to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology," according to NASA.
Finalists will be announced at the end of the year, and NASA will explore those mission concepts further.
"For future missions to Saturn, there are a lot of possibilities," Spilker said. "One certainly involves the tiny moon Enceladus and the potential for life in that global ocean. The potential for astrobiology in the ocean on Titan. There's questions about the rings - can we get even closer and understand those individual ring particles? Lots of questions remain, so that's why we have to go back."
Cassini has monitored Enceladus (313 miles or 504 kilometers across) with a particular interest in the plumes and the geology of the south polar region for many years. Different viewing geometries give scientists different information, and the resulting animation gives us a unique “spacecraft’s eye” view of the flyby. The movie is a composite of six images taken with the Cassini spacecraft narrow-angle camera on Aug. 1, 2017 using filters that allow infrared, green, and ultraviolet light. The image filter centered on 930 nm (IR) is red in this image, the image filter centered on the green is green, and the image filter centered on 338 nm (UV) is blue. The view was obtained at a distance of approximately 112,000 miles (181,000 kilometers) from Enceladus. Image scale is about 0.6 mile (1 kilometer) per pixel.
A new study in the journal Nature Astronomy reports that the south polar region of Saturn's icy moon Enceladus is warmer than expected just a few feet below its icy surface. This suggests that Enceladus' ocean of liquid water might be only a couple of miles beneath this region - closer to the surface than previously thought. The excess heat is especially pronounced over three fractures that are not unlike the "tiger stripes" - prominent, actively venting fractures that slice across the pole - except that they don't appear to be active at the moment. Seemingly dormant fractures lying above the moon's warm, underground sea point to the dynamic character of Enceladus' geology, suggesting the moon might have experienced several episodes of activity, in different places on its surface. The finding agrees with the results of a 2016 study by a team independent of the Cassini mission that estimated the thickness of Enceladus' icy crust. The studies indicate an average depth for the ice shell of 11 to 14 miles (18 to 22 kilometers), with a thickness of less than 3 miles (5 kilometers) at the south pole. "Finding temperatures near these three inactive fractures that are unexpectedly higher than those outside them adds to the intrigue of Enceladus," said Cassini Project Scientist Linda Spilker at NASA's Jet Propulsion Laboratory, Pasadena, California. "What is the warm underground ocean really like and could life have evolved there? These questions remain to be answered by future missions to this ocean world.".
Illustration of the interior of Saturn's moon Enceladus / image by NASA, JPL-Caltech / source NASA.gov
A global ocean lies beneath the icy crust of Saturn's geologically active moon Enceladus, according to new research using data from NASA's Cassini mission. Researchers found the magnitude of the moon's very slight wobble, as it orbits Saturn, can only be accounted for if its outer ice shell is not frozen solid to its interior, meaning a global ocean must be present. The finding implies the fine spray of water vapor, icy particles and simple organic molecules Cassini has observed coming from fractures near the moon's south pole is being fed by this vast liquid water reservoir. The research is presented in a paper published online this week in the journal Icarus. Previous analysis of Cassini data suggested the presence of a lens-shaped body of water, or sea, underlying the moon's south polar region. However, gravity data collected during the spacecraft's several close passes over the south polar region lent support to the possibility the sea might be global. The new results - derived using an independent line of evidence based on Cassini's images - confirm this to be the case.
New ocean world discoveries from Cassini and Hubble will help inform future exploration and the broader search for life beyond Earth.
A big enough impact could potentially break up a moon. Luckily for Mimas, whatever created Herschel was not quite big enough to cause that level of disruption. When large impacts happen, they deliver tremendous amounts of energy -- sometimes enough to cause global destruction. Even impacts that are not catastrophic can leave enormous, near-permanent scars on bodies like Mimas (246 miles or 396 kilometers across). This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 32 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 19, 2016. The view was acquired at a distance of approximately 53,000 miles (85,000 kilometers) from Mimas. Image scale is 1,677 feet (511 meters) per pixel.
When viewed from a distance with the sun directly behind Cassini, the larger, brighter craters really stand out on moons like Dione. Among these larger craters, some leave bright ray patterns across the moon, calling attention to their existence and to the violence of their creation. The rayed crater seen here on Dione (698 miles, or 1,123 kilometers across) is named Creusa. The rays are brighter material blasted out by the impact that formed the crater. Scientists can use the patterns of ejecta (like these rays), to help determine the order of geological events on a moon's surface by examining which features lie on top of other features. This view looks toward the Saturn-facing side of Dione. North on Dione is up and rotated 31 degrees to the right. The image was taken with the Cassini spacecraft narrow-angle camera on Nov. 26, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 727 nanometers. The view was obtained at a distance of approximately 350,000 miles (560,000 kilometers) from Dione. Image scale is 1.8 miles (3 kilometers) per pixel.
This zoomed-in view of Epimetheus, one of the highest resolution ever taken, shows a surface covered in craters, vivid reminders of the hazards of space. Epimetheus (70 miles or 113 kilometers across) is too small for its gravity to hold onto an atmosphere. It is also too small to be geologically active. There is therefore no way to erase the scars from meteor impacts, except for the generation of new impact craters on top of old ones. This view looks toward anti-Saturn side of Epimetheus. North on Epimetheus is up and rotated 32 degrees to the right. The image was taken with the Cassini spacecraft narrow-angle camera on Feb. 21, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 939 nanometers. The view was acquired at a distance of approximately 9,300 miles (15,000 kilometers) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 71 degrees. Image scale is 290 feet (89 meters) per pixel.
Cassini bids farewell to Saturn’s yin-and-yang moon, Iapetus. This image is from the last set of observations Cassini made of this world of striking contrasts. The spacecraft helped scientists better understand Iapetus, solving a centuries-old mystery of why it should be bright on one side and dark on the other. Cassini observations of Iapetus (914 mile or 1471 kilometers across) support the prevailing theory that led to the understanding that the dichotomy of the surface is due to a combination of infalling dust from outside of the moon followed by a migration of water ice from the darker (therefore warmer) areas to the cold, brighter surfaces. This false-color view is a composite of individual frames obtained using filters sensitive to ultraviolet (centered at 338 nanometers), green (centered at 568 nanometers) and infrared light (centered at 930 nanometers). The view has been enhanced to accentuate subtle color differences and fine-scale surface features. This view looks toward the Saturn-facing hemisphere of Iapetus. North on Iapetus is up and rotated 12 degrees to the left. The view was acquired on May 30, 2017, at a distance of approximately 1.5 million miles (2.5 million kilometers) from Iapetus. Image scale is 9 miles (15 kilometers) per pixel.
Saturn's active, ocean-bearing moon Enceladus sinks behind the giant planet in a farewell portrait from NASA's Cassini spacecraft. This view of Enceladus was taken by NASA's Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back. The view is part of a movie sequence of images taken over a period of 40 minutes as the icy moon passed behind Saturn from the spacecraft's point of view. Images taken using red, green and blue spectral filters were assembled to create the natural color view. (A monochrome version of the image, taken using a clear spectral filter, is also available.) The images were taken using Cassini's narrow-angle camera at a distance of 810,000 million miles (1.3 million kilometers) from Enceladus and about 620,000 miles (1 million kilometers) from Saturn. Image scale on Enceladus is 5 miles (8 kilometers) per pixel.
The colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft. The north polar hood can be seen on Titan (3200 miles, 5150 kilometers across) and appears as a detached layer at the top of the moon here. This view looks toward the northern, sunlit side of the rings from just above the ring plane. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained with the Cassini spacecraft narrow-angle camera on May 21, 2011 at a distance of approximately 1.4 million miles (2.3 million kilometers) from Titan. Image scale is 9 miles (14 kilometers) per pixel on Titan.
With this view, Cassini captured one of its last looks at Saturn and its main rings from a distance. The Saturn system has been Cassini's home for 13 years, but that journey is nearing its end. Cassini has been orbiting Saturn for nearly a half of a Saturnian year but that journey is nearing its end. This extended stay has permitted observations of the long-term variability of the planet, moons, rings, and magnetosphere, observations not possible from short, fly-by style missions.
Saturn's northern hemisphere reached its summer solstice in mid-2017, bringing continuous sunshine to the planet's far north. The solstice took place on May 24, 2017. The Cassini mission is using the unparalleled opportunity to observe changes that occur on the planet as the Saturnian seasons turn. This view looks toward the sunlit side of the rings from about 17 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on April 17, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 939 nanometers. The view was acquired at a distance of approximately 733,000 miles (1.2 million kilometers) from Saturn. Image scale is 44 miles (70 kilometers) per pixel.
This image of Saturn's northern hemisphere was taken by NASA's Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth. The view was taken in visible red light using the Cassini spacecraft wide-angle camera at a distance of 684,000 miles (1.1 million kilometers) from Saturn. Image scale is 40 miles (64 kilometers).
This image of Saturn's rings was taken by NASA's Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth. The view was taken in visible red light using the Cassini spacecraft wide-angle camera at a distance of 684,000 miles (1.1 million kilometers) from Saturn.
Cassini gazes across the icy rings of Saturn toward the icy moon Tethys, whose night side is illuminated by Saturnshine, or sunlight reflected by the planet. Tethys was on the far side of Saturn with respect to Cassini here; an observer looking upward from the moon's surface toward Cassini would see Saturn's illuminated disk filling the sky. Tethys was brightened by a factor of two in this image to increase its visibility. A sliver of the moon's sunlit northern hemisphere is seen at top. A bright wedge of Saturn's sunlit side is seen at lower left. This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on May 13, 2017. The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. Image scale is 43 miles (70 kilometers) per pixel on Saturn. The distance to Tethys was about 930,000 miles (1.5 million kilometers). The image scale on Tethys is about 56 miles (90 kilometers) per pixel.
This image of Saturn's outer A ring features the small moon Daphnis and the waves it raises in the edges of the Keeler Gap. The image was taken by NASA's Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth. The view was taken in visible light using the Cassini spacecraft wide-angle camera at a distance of 486,000 miles (782,000 kilometers) from Saturn. Image scale is 2.7 miles (4.3 kilometers).
This view of Saturn's A ring features a lone "propeller" -- one of many such features created by small moonlets embedded in the rings as they attempt, unsuccessfully, to open gaps in the ring material. The image was taken by NASA's Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth. The view was taken in visible light using the Cassini spacecraft wide-angle camera at a distance of 420,000 miles (676,000 kilometers) from Saturn. Image scale is 2.3 miles (3.7 kilometers).
The north pole of Saturn sits at the center of its own domain. Around it swirl the clouds, driven by the fast winds of Saturn. Beyond that orbits Saturn's retinue of moons and the countless small particles that form the ring. Although the poles of Saturn are at the center of all of this motion, not everything travels around them in circles. Some of the jet-stream patterns, such as the hexagon-shaped pattern seen here, have wavy, uneven shapes. The moons as well have orbits that are elliptical, some quite far from circular. This view looks toward the sunlit side of the rings from about 26 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Dec. 2, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 890 nanometers. The view was acquired at a distance of approximately 619,000 miles (996,000 kilometers) from Saturn. Image scale is 37 miles (60 kilometers) per pixel.
Saturn's north polar hexagon basks in the Sun's light now that spring has come to the northern hemisphere. Many smaller storms dot the north polar region and Saturn's signature rings, which appear to disappear on account of Saturn's shadow, put in an appearance in the background. The north polar hexagon was first observed by Voyager. The image was taken with the Cassini spacecraft's wide-angle camera on Nov. 27, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 750 nanometers. The view was acquired at a distance of approximately 403,000 miles (649,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 21 degrees. Image scale is 22 miles (35 kilometers) per pixel.
These turbulent clouds are on top of the world at Saturn / image by NASA, JPL-Caltech / source NASA.gov
NASA's Cassini spacecraft captured this view of Saturn's north pole on April 26, 2017 - the day it began its Grand Finale -- as it approached the planet for its first daring dive through the gap between the planet and its rings. Although the pole is still bathed in sunlight at present, northern summer solstice on Saturn occurred on May 24, 2017, bringing the maximum solar illumination to the north polar region. Now the Sun begins its slow descent in the northern sky, which eventually will plunge the north pole into Earth-years of darkness. Cassini's long mission at Saturn enabled the spacecraft to see the Sun rise over the north, revealing that region in great detail for the first time. This view looks toward the sunlit side of the rings from about 44 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 166,000 miles (267,000 kilometers) from Saturn. Image scale is about 10 miles (16 kilometers) per pixel.
This monochrome view is the last image taken by the imaging cameras on NASA's Cassini spacecraft. It looks toward the planet's night side, lit by reflected light from the rings, and shows the location at which the spacecraft would enter the planet's atmosphere hours later.
Cassini has been orbiting Saturn since June 2004, studying the planet, its rings and its moons. A final close flyby of Saturn's moon Titan on April 22 will reshape the Cassini spacecraft's orbit so that it begins its final series of 22 weekly dives through the unexplored gap between the planet and its rings. The first of these dives is planned for April 26. Following these closer-than-ever encounters with the giant planet, Cassini will make a mission-ending plunge into Saturn's upper atmosphere on Sept. 15.
Friday, Sept. 15, 7-8:30 a.m. EDT: Cassini mission's "Grand Finale." Live commentary. See inside mission control as we awaited the FINAL signal and science data from our Cassini spacecraft. After two decades in space, NASA's Cassini mission to Saturn is at the end of its remarkable journey of exploration.
Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, awaited the final transmission from the Cassini spacecraft as it plunged into Saturn's atmosphere ending its 20-year voyage of discovery.