Launched on October 15, 1997, NASA’s Cassini spacecraftNotes 1 went into orbit around Saturn on July 1, 2004. Since then, it has taken thousands of photos of Saturn, the second-largest planet in the Solar System, its prominent rings, and moons. And on September 15, 2017, Cassini plunged into Saturn’s atmosphere and disintegrated. Here are the 20 most beautiful photos that the spacecraft has sent back to Earth during its 13-year voyage around the gas giant.
Cassini was destroyed by diving into the Saturn’s atmosphere on September 15, 2017. This method of disposal was planned to avoid potential biological contamination of Saturn’s moons, since Titan, Enceladus, and other icy moons of Saturn may harbor oceans and alien life.
With the original titles given by NASA:
1. The Day the Earth Smiled: Sneak Preview
In the 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. Earth, which is 898 million miles (1.44 billion kilometers) away in this image, appears as a blue dot at center right; the moon can be seen as a fainter protrusion off its right side. If you couldn’t spot the Earth, you can also see the annotated version.
“Consider again that dot [Earth]. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.” Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space
You can also see Cassini’s Last View of Earth (Earth between the rings of Saturn)
2. So Far from Home
Taken on October 28, 2016, it was one of Cassini’s last looks at Saturn and its main rings from a distance (approximately 870,000 miles / 1.4 million kilometers). The planet’s northern hemisphere is seen here at top. This view looks toward the sunlit side of the rings from about 25 degrees above the ringplane. Images taken with the wide angle camera using red, green and blue spectral filters were combined to create this color view.
3. True Colors
The gas giant’s dark-side rings glow in shades of brown and gold, contrasting with the more neutral appearance of the icy moon Tethys, which is 1,062 kilometers, or 660 miles across. This view looks toward the anti-Saturn side of Tethys and the unilluminated side of the rings from about 2 degrees above the ringplane. North is up and rotated 35 degrees to the right.
Images taken using red, green and blue spectral filters were combined to create this natural color view. The view was acquired with the Cassini spacecraft narrow-angle camera on October 29, 2007, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 21 degrees.
Tethys was discovered by the Italian astronomer Giovanni Domenico Cassini (8 June 1625 – 14 September 1712) in 1684, together with Dione, another moon of Saturn, and is named after the titan Tethys of Greek mythology. The Italian astronomer named the four moons he discovered (Tethys, Dione, Rhea and Iapetus) Sidera Lodoicea (“the stars of Louis”) to honor king Louis XIV (5 September 1638 – 1 September 1715), known as Louis the Great (Louis le Grand) or the Sun King (le Roi Soleil), was a monarch of the House of Bourbon who reigned as King of France from 1643 until his death in 1715.
Tethys has a low density of 0.98 g/cm3, the lowest of all the major moons in the Solar System, indicating that it is made of water ice with just a small fraction of rock. This is confirmed by the spectroscopy of its surface. The largest impact crater on Tethys, which can be seen in the image above, Odysseus, is about 250 miles (400 km) in diameter.
4. Titan Up Front
In the true color photo above which taken on May 21, 2011, the colorful globe of Titan passes in front of Saturn and its rings. The north polar hood can be seen on Titan 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.
5. Earth’s Twin Seen From Saturn
Peering over the shoulder of giant Saturn, through its rings, and across interplanetary space, Cassini spies the bright, cloudy terrestrial planet, Venus. The vast distance from Saturn means that Venus only shows up as a white dot, just above and to the right of the image center.
This view looks toward the unilluminated side of the rings from about 17 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on November 10, 2012.
Venus is one of the four terrestrial planets in the Solar System, so it is a rocky body like Earth. It is also similar to Earth in size and mass, and is often described as Earth’s “sister” or “twin”. But the similarity ends here, since Venus has an atmosphere of carbon dioxide that reaches nearly 900 degrees Fahrenheit (500 degrees Celsius) and a surface pressure 100 times that of Earth.
6. Catching Its Tail
You can see a huge storm (the largest, most intense storm observed on Saturn by NASA’s Voyager or Cassini spacecraft) churning through the atmosphere in Saturn’s northern hemisphere overtakes itself as it encircles the planet in this true-color view. THis image is captured on February 25, 2011. The storm was already begun twelve days ago. During that time, some of the clouds moved south. This tail, which appears as slightly blue clouds south and west (left) of the storm head, can be seen encountering the storm head in this view.
Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired with the Cassini spacecraft wide-angle camera at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn.
Huge storms called Great White Spots have been observed in previous Saturnian years (1 Saturnean year is about 30 Earth years), usually appearing in late northern summer. But, neither the Voyager nor the Cassini spacecraft were at Saturn for previous Great White Spot appearances. At the time the images were taken, Saturn was experiencing early northern spring, so this storm, if it is a Great White Spot, was happening earlier than usual.
7. Titan and Dione
Saturn’s fourth-largest moon, Dione (698 miles or 1,123 kilometers across), can be seen through the haze of the planet’s largest moon, Titan (3,200 miles or 5,150 kilometers across), in this view of the two posing before the planet and its rings.
Titan is the only moon known to have a dense atmosphere, and the only object in space other than Earth where clear evidence of stable bodies of surface liquid has been found. Many of the gases that make up Titan’s brown haze were hydrocarbons, theoretically formed via the recombination of radicals created by the Sun’s ultraviolet photolysis of methane.
Titan is primarily composed of water ice and rocky material. Its climate, including wind and rain, creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas (probably of liquid methane and ethane), and deltas, and is dominated by seasonal weather patterns as on Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan’s methane cycle is analogous to Earth’s water cycle, at the much lower temperature of about 94 K (−179.2 °C).
In the photo, north is up on the moons. 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 and 2 million miles (3.2 million kilometers) from Dione.
8. Painted Lines on an Ornament
In the image taken on July 22, 2013, Saturn’s hexagon can be seen here in true color. It is a very large persisting hexagonal cloud pattern around the north pole of Saturn. The sides of the hexagon are about 8,600 miles (13,800 km) long, which is more than the diameter of Earth (about 7,900 miles / 12,700 km). Sometimes it is easy to forget just how large Saturn is: with a diameter of about 72,400 miles (116,500 kilometers), it is around 10 times wider than the Earth.
This view was acquired at a distance of approximately 611,000 miles (984,000 kilometers) from Saturn.
9. Saturn by Gordan Ugarkovic
This view of Saturn was created made by amateur image processor and Cassini fan Gordan Ugarkovic from images obtained on October 10, 2013. It was chosen as NASA’s image of the day for October 17, 2013. You can see the full-resolution image on NASA’s web site.
10. Saturn-lit Tethys
In the image taken on May 13, 2017, the night side of Tethys, the icy moon of Saturn is illuminated by the sunlight reflected by the planet. Tethys’ sunlit northern hemisphere is seen at top.
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. The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn. Cassini’s distance to Tethys was about 930,000 miles (1.5 million kilometers).
11. Not Really Starless at Saturn
Usually there are no stars appear in the images of Saturn, because its main rings, along with its body and moons, are much brighter than most stars. As a result, much shorter exposure times (10 milliseconds, in this case) are required to produce an image. To capture the stars, a longer exposure would be required. Cassini has captured stars on many occasions, especially when a target moon is in eclipse, and thus darker than normal. A beautiful example is the next photo (Number 13) titled “Starry Night”.
Above the rings, Dione (698 miles, 1123 kilometers across) and Epimetheus (70 miles, 113 kilometers across) can be seen at left and right respectively. The image was taken on April 2, 2016 at a distance of approximately 257,000 miles (413,000 kilometers) from Saturn.
12. Starry Night
This photo of Enceladus was captured on October 9, 2008 while the moon was in eclipse, within Saturn’s shadow. Thus, a lot of stars can be seen.
With a diameter of about 310 miles (500 kilometers), Enceladus is the sixth-largest moon of Saturn. It was discovered on August 28, 1789, by William Herschel (15 November 1738 – 25 August 1822), the a British astronomer and composer of German and Czech-Jewish origin. Enceladus is mostly covered by fresh, clean ice, making it one of the most reflective bodies of the solar system. It is is named after the giant Enceladus of Greek mythology.
Enceladus is considered as one of the most scientifically compelling bodies in our solar system. It has an underground ocean beneath an icy crust. Hydrothermal vents spew water vapor and ice particles from that ocean and this plume of material includes organic compounds, volatile gases, carbon dioxide, carbon monoxide, salts and silica.
With its global ocean, unique chemistry and internal heat, Enceladus has become a promising lead in the search for extraterrestrial life.
This photo was taken at a distance of approximately 83,000 kilometers (52,000 miles) from Enceladus.
13. Dione with Rings and Shadows
Dione, the fourth-largest moon of Saturn (and the 15th largest moon in the Solar System) hangs in front of the gas giant and its icy rings. This photo was captured on August 17, 2015 during Cassini’s final close flyby of the icy moon. North on Dione is up. The image was obtained in visible light at a distance of approximately 45,000 miles (73,000 kilometers) from Dione.
It has probably a huge ocean, under an icy shell, like Enceladus, which is buried about 60 miles (100 kilometers) beneath the shell.
14. Flying by the ‘Death Star’ Moon
This view of the Mimas was captured on February 13, 2010 on Cassini’s closest-ever flyby of the moon at a distance about 5,900 miles (9,500 kilometers). This mosaic was created from six images taken that day in visible light with Cassini’s narrow-angle camera. Mimas’ most distinctive feature is a giant impact crater 81 miles (130 kilometers) across, named after William Herschel, the discoverer of Mimas. The Herschel crater makes Mimas look like the Death Star in the movie “Star Wars.”
The moon is named after Mimas, a son of Gaia in Greek mythology who was killed by Mars in the war between the Titans and the gods of Olympus. Even after his death, Mimas’ legs -which were serpents- hissed vengeance and sought to attack his killer.
Mimas was named by John Herschel, the son of discoverer William Herschel, who explained his choice of names for the first seven of Saturn’s moons to be discovered by writing, “As Saturn devoured his children, his family could not be assembled round him, so that the choice lay among his brothers and sisters, the Titans and Titanesses.”
Astronomers also refer to Mimas as “Saturn I” based on its distance being the closest to Saturn. With a diameter of 246 miles (396 kilometers) it is the smallest astronomical body that is known to be rounded in shape because of self-gravitationNotes 2.
15. Fire and Ice
Two largest moons of Saturn, Titan (1st) and Rhea (2nd) appear to be stacked on top of each other in this true-color scene. This view was obtained on June 16, 2011 at a distance of approximately 1.1 million miles (1.8 million kilometers) from Rhea and 1.5 million miles (2.5 million kilometers) from Titan and looks toward the Saturn-facing side of Rhea.
Rhea is the second-largest moon of Saturn (949 miles or 1528 kilometers across) and the ninth-largest moon in the Solar System. It is also the second smallest body in the Solar System which precise measurements have confirmed a shape consistent with hydrostatic equilibriumNotes 3 (the smallest is the asteroid and dwarf planet Ceres, the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter, which has a diameter of approximately 587 miles / 945 kilometers).
Rhea was discovered by Giovanni Domenico Cassini on 23 December 1672.
16. Two Moons Passing in the Night
Mimas “the dead star moon” and Pandora can be seen in the image above which obtained on May 14, 2013, at a distance of approximately 690,000 miles (1.1 million kilometers) from Mimas. The image was taken in blue light with the Cassini spacecraft narrow-angle camera and looks toward the anti-Saturn hemisphere of Mimas.
17. Moons Small to Large
In the photo which taken on January 15, 2011, Saturn’s largest moon, Titan (3,200 miles or 5,150 kilometers), is in the center of the image. The smaller moon Enceladus (313 miles or 504 kilometers across) is on the far right, appearing just below the rings. The tiny moon Pandora (81 kilometers, or 50 miles across) is barely detectable as a speck on the far left, beyond the thin F ring. To enhance visibility, Pandora has been brightened by a factor of two relative to the rest of the image. The view was acquired at a distance of approximately 524,000 miles (844,000 kilometers) from Titan.
18. Big and Small Before Rings
In the photo taken in visible green light with the Cassini’s narrow-angle camera on March 24, 2010, Saturn’s moon Rhea looms “over” a smaller and more distant Epimetheus against a strikingly beautiful background of planet and rings.
The two moons aren’t actually close to each other. The view was obtained at a distance of approximately 746,000 miles (1.2 million kilometers) from Rhea and 994,000 miles (1.6 million kilometers) from Epimetheus.
19. Mimas by Saturnshine
Here Mimas, the “death star” moon (at the upper right) is illuminated by “Saturnshine.” The image was taken on February 16, 2015 in visible light at a distance of approximately 1.6 million miles (2.5 million kilometers) from Mimas.
20. The Greatest Saturn Portrait… Yet
On October 6, 2004, Cassini captured a series of images that have been composed into the largest, most detailed, global natural color view of Saturn and its rings ever made (to date). The images were taken over the course of two hours while Cassini was approximately 6.3 million kilometers (3.9 million miles) from Saturn.
This grand mosaic consists of 126 images acquired in a tile-like fashion: three images (red, green and blue) were taken of each of 42 locations, or “footprints”, across the planet. The full color footprints were put together to produce a mosaic that is 8,888 pixels across and 4,544 pixels tall. Many of Saturn’s splendid features noted previously in single frames taken by Cassini are visible in this one detailed, all-encompassing view: subtle color variations across the rings, the thread-like F ring, ring shadows cast against the blue northern hemisphere, the planet’s shadow making its way across the rings to the left, and blue-grey storms in Saturn’s southern hemisphere to the right. Tiny Mimas and even smaller Janus are both faintly visible at the lower left (you can see these details in the full-resolution image on NASA web site).
Tribute to Cassini
And a beautiful tribute to Cassini from NASA’s NASA Jet Propulsion Laboratory. The spacecraft has been orbiting Saturn for 13 years, or nearly half of a Saturnian year.
Cassini’s Infrared Saturn: the video below explores Cassini CIRS’ Greatest Hits, as told by instrument team members Michael Flasar, Conor Nixon, and Carrie Anderson.
NASA Mission Control Live: Cassini’s Finale at Saturn. The video below is the recorded version of NASA’s live stream.
“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.”
- The name of the spacecraft is actually Cassini–Huygens, but it is commonly called Cassini. It was a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency (ASI). The spacecraft, named after astronomers Giovanni Cassini and Christiaan Huygens, comprised both NASA’s Cassini probe, and ESA’s Huygens lander which would be landed on Saturn’s largest moon, Titan. Cassini released the Huygens probe on December 25, 2004, by means of a spring and spiral rails intended to rotate the probe for greater stability. It entered the atmosphere of Titan on January 14, 2005, and after a two-and-a-half-hour descent landed on solid ground. Cassini successfully relayed 350 of the pictures that it received from Huygens of its descent and landing site. Unfortunately one of the Cassini receivers failed due to a software error and caused the loss of another 350 pictures.
- According to NASA, Mimas is not quite big enough to hold a round shape, so it is somewhat ovoid with dimensions of 129 x 122 x 119 (miles 207 x 197 x 191 km, respectively) (Source). But it looks round enough, and it is also included in the “List of gravitationally rounded objects of the Solar System” on wikipedia, so I gave it the number zero.
- In fluid mechanics, a fluid is said to be in hydrostatic equilibrium or hydrostatic balance when it is at rest, or when the flow velocity at each point is constant over time. This occurs when external forces such as gravity are balanced by a pressure gradient force. For instance, the pressure-gradient force prevents gravity from collapsing Earth’s atmosphere into a thin, dense shell, whereas gravity prevents the pressure gradient force from diffusing the atmosphere into space. Hydrostatic equilibrium is the current distinguishing criterion between dwarf planets and small Solar System bodies, and has other roles in astrophysics and planetary geology. This qualification typically means that the object is symmetrically rounded into a spheroid or ellipsoid shape, where any irregular surface features are due to a relatively thin solid crust. There are 31 observationally confirmed such objects (apart from the Sun), sometimes called planemos, in the Solar System, seven more that are virtually certain, and a hundred or so more that are likely.