The Pioneer 11 spacecraft launched from Cape Canaveral forty years ago, on April 5, 1973. Pioneer 11’s path through Saturn’s outer rings took it within 21,000 km of the planet, where it discovered two new moons (almost smacking into one of them in September 1979) and a new “F” ring. The spacecraft also discovered and charted the magnetosphere, magnetic field and mapped the general structure of Saturn’s interior. The spacecraft’s instruments measured the heat radiation from Saturn’s interior and found that its planet-sized moon, Titan, was too cold to support life.
This image from Pioneer 11 shows Saturn and its moon Titan. The irregularities in ring silhouette and shadow are due to technical anomalies in the preliminary data later corrected. At the time this image was taken, Pioneer was 2,846,000 km (1,768,422 miles) from Saturn.
Image credit: NASA Ames
A giant of a moon appears before a giant of a planet undergoing seasonal changes in this natural color view of Titan and Saturn from NASA’s Cassini spacecraft.
Titan, Saturn’s largest moon, measures 3,200 miles, or 5,150 kilometers, across and is larger than the planet Mercury. Cassini scientists have been watching the moon’s south pole since a vortex appeared in its atmosphere in 2012. See PIA14919 and PIA14920 to learn more about this mass of swirling gas around the pole in the atmosphere of the moon.
As the seasons have changed in the Saturnian system, and spring has come to the north and autumn to the south, the azure blue in the northern Saturnian hemisphere that greeted Cassini upon its arrival in 2004 is now fading. The southern hemisphere, in its approach to winter, is taking on a bluish hue. This change is likely due to the reduced intensity of ultraviolet light and the haze it produces in the hemisphere approaching winter, and the increasing intensity of ultraviolet light and haze production in the hemisphere approaching summer. (The presence of the ring shadow in the winter hemisphere enhances this effect.) The reduction of haze and the consequent clearing of the atmosphere makes for a bluish hue: the increased opportunity for direct scattering of sunlight by the molecules in the air makes the sky blue, as on Earth. The presence of methane, which generally absorbs in the red part of the spectrum, in a now clearer atmosphere also enhances the blue.
This view looks toward the northern, sunlit side of the rings from just above the ring plane.
This mosaic combines six images — two each of red, green and blue spectral filters — to create this natural color view. The images were obtained with the Cassini spacecraft wide-angle camera on May 6, 2012, at a distance of approximately 483,000 miles (778,000 kilometers) from Titan. Image scale is 29 miles (46 kilometers) per pixel on Titan.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Image Credit: NASA/JPL-Caltech/SSI
This false-color image shows evidence for lakes of liquid hydrocarbons, probably methane or ethane, on Titan’s surface. The lakes are represented as dark areas, but are not what the human eye would see, because radar was used to penetrate the thick haze obscuring Titan’s surface. The Cassini radar instrument acquired this image on July 22, 2006. The image is centered near 80 degrees north, 35 degrees west and is about 140 kilometers (84 miles) across. The strip of radar imagery is foreshortened to simulate an oblique view of the highest latitude region, seen from a point to its west. Smallest details in this image are about 500 meters (1,640 feet) across.Credit: NASA/JPL/USGS
Ontario Lacus is Titan’s largest lake in its southern hemisphere. It is an ephemeral lake that resembles Etosha Pan in Namibia, Africa. On Titan the liquid is made of hydrocarbons, whereas on Earth it is made of water.Credits: Cassini radar image JPL/NASA. Envisat radar image ESA. Composite image: LPGNantes.
This artist’s concept shows a possible model of Titan’s internal structure that incorporates data from NASA’s Cassini spacecraft. In this model, Titan is fully differentiated, which means the denser core of the moon has separated from its outer parts. This model proposes a core consisting entirely of water-bearing rocks and a subsurface ocean of liquid water. The mantle, in this image, is made of icy layers, one that is a layer of high-pressure ice closer to the core and an outer ice shell on top of the sub-surface ocean.Image credit: A. D. Fortes/UCL/STFC
A model of Cassini is shown making a targeted flyby over Titan’s cloudtops, with Saturn and Enceladus appearing at upper right.
The model, developed by Dominic Fortes of University College London, England, incorporates data from Cassini’s radio science experiment.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The radio science team is based at Wellesley College, Wellesley, Mass.
Craters appear well defined on icy Rhea in front of the hazy orb of the much larger moon Titan in this Cassini spacecraft view of these two Saturn moons.Image credit: NASA/JPL-Caltech/Space Science Institute
Lit terrain seen here is on the leading hemispheres of Rhea and Titan. North on the moons is up and rotated 13 degrees to the left. The limb, or edge of the visible disk, of Rhea is slightly overexposed in this view.
The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on Dec. 10, 2011. The view was acquired at a distance of approximately 1.2 million miles (2 million kilometers) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 109 degrees. The view was acquired at a distance of approximately 810,000 miles (1.3 million kilometers) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 109 degrees. Image scale is 8 miles (12 kilometers) per pixel on Titan and 5 miles (8 kilometers) per pixel on Rhea.
This view from NASA’s Cassini spacecraft looks toward the south polar region of Saturn’s largest moon, Titan, and shows a depression within the moon’s orange and blue haze layers near the south pole.Image Credit: NASA/JPL-Caltech/Space Science Institute
The moon’s high altitude haze layer appears blue here; whereas, the main atmospheric haze is orange. The difference in color could be due to particle size of the haze. The blue haze likely consists of smaller particles than the orange haze.
The depressed or attenuated layer appears in the transition area between the orange and blue hazes about a third of the way in from the left edge of the narrow-angle image. The moon’s south pole is in the upper right of this image. This view suggests Titan’s north polar vortex, or hood, is beginning to flip from north to south.
The southern pole of Titan is going into darkness as the sun advances towards the north with each passing day. The upper layer of Titan’s hazes is still illuminated by sunlight.
Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained on Sept. 11, 2011 at a distance of approximately 83,000 miles (134,000 kilometers) from Titan. Image scale is 2,581 feet (787 meters) per pixel.
Near-infrared color composite image of Saturn’s largest moon Titan (via W. M. Keck Observatory)