Saturn's Moon Titan
A pair of Saturn's many moons joins the planet in this Cassini spacecraft scene, appearing as small white dots. Image Credit & Copyright: NASA/JPL-Caltech/Space Science Institute
Saturn's Moon Rhea
Rhea, the second largest moon of Saturn, is a dirty snowball of rock and ice. Rhea is only moon with an oxygen atmosphere, thin though it may be. Rhea is also one of the most heavily cratered satellites in the solar system.
Rhea's Profile:
Age: About 4.6 billion years old, the same age as Saturn.
Distance from Saturn: Rhea's average orbital distance is 327,505 miles (527,068 km). As a result of its distance, Saturn's gravitational tug has less of an effect on the moon.
Size: At 949 miles (1,528 kilometers) in diameter, Rhea is the second largest moon of Saturn, but less than a third the size of the largest contender, Titan.
Temperature: Temperatures on Rhea range from minus 174 degrees C (minus 281 degrees F) in the warmer, sunlit areas to minus 220 C (minus 364 F) in the shade. At these frigid temperatures, the ice on the moon behaves like rock.
Saturn, the sixth planet from the sun, is home to a vast array of intriguing and unique worlds. From the cloud-shrouded surface of Titan to crater-riddled Phoebe, each of Saturn's moons tells another piece of the story surrounding the Saturn system.
Saturn has about 62 known moons, most notably Titan, Rhea, and Enceladus.
Enceladus displays at least five different types of terrain. Parts of Enceladus shows craters no larger than 35 km in diameter. Other areas show regions with no craters, indicating major resurfacing events in the geologically recent past. There are fissures, plains, corrugated terrain, geysers that indicate that the interior of the moon may be liquid today, even though it should have frozen eons ago.
Saturn's Moon Enceladus
Enceladus' Profile:
Age: About 4.5 billion years old.
Distance from Saturn: Enceladus orbits an average of only 147,909 miles (238,037 km) around Saturn. It's orbital period is 1.37 Earth days.
Size: Enceladus, with a diameter of 314 miles (505 kilometers), is small enough to fit inside the borders of the state of Arizona. It is the sixth largest and most massive moon of Saturn.
Temperature: Because the planet reflects sunlight rather than absorbing it, it reaches temperatures as low as minus 201 degrees C (minus 330 degrees F).
Titan is Saturn's largest moon. It is surrounded by a thick, golden haze, and only certain kinds of telescopes and cameras can see through the haze to the surface. Titan is of great interest to scientists because it has flowing liquids on its surface and a dense, complex atmosphere.
Titan's Profile:
Age: About 4.5 billion years old, the same age as Saturn.
Distance from the sun: On average, Titan's distance from the sun is about 1.4 billion km.
Distance from Saturn: Titan is Saturn's largest satellite. Its orbital distance from Saturn is 759,000 miles (1,221,830 km) and Titan's orbital period is 15,945 days.
Size: Titan is 3,200 miles (5,150 km) in diameter, making it larger than Earth's moon. It is the 2nd largest moon in the solar system.
Temperature: Titan's surface temperature is approximately minus 290 Fahrenheit (minus 179 degrees Celsius), which makes water as hard as rocks and allows methane to be found in its liquid form
Ligeia Mare, shown here in a false-color image from NASA's Cassini mission, is the second largest known body of liquid on Saturn's moon Titan. It is filled with liquid hydrocarbons, such as ethane and methane, and is one of the many seas and lakes that on Titan's north polar region. Image Credit & Copyright: NASA/JPL-Caltech/ASI/Cornell
Titan: The Possibility of Life
It is thought that conditions on Titan could make the moon more habitable in the far future. If the sun increases its temperature (6 billion years from now) and becomes a red giant star, Titan's temperature could increase enough for stable oceans to exist on the surface, according to some models. If this happens, conditions in Titan could be similar to Earth's, allowing conditions favorable for some forms of life.
Titan's "Magic Islands"
Using radar aboard NASA's Cassini spacecraft, Jason Hofgartner, a planetary scientist at Cornell University, and his colleagues peered through Titan's thick, hazy atmosphere to analyze Ligeia Mare, the second-largest sea on Titan. A mysteriously bright anomaly winked in and out of existence on the seas of Saturn's largest moon, Titan — potentially the first time waves, bubbles or some other unknown features have been seen there. Prior to the July 2013 data, the region the scientists analyzed was completely devoid of features, including waves. However, in July 2013, Cassini detected features that are essentially as bright as the surrounding terrain. This can be seen in the below image. The anomaly disappeared after subsequent observations. Scientists plan to study this anomaly further to learn the cause.
Using a special spectral filter, the high-resolution camera aboard NASA's Cassini spacecraft was able to peer through the hazy atmosphere of Saturn's moon Titan. Image Credit & Copyright: Galileo Project, NASA/JPL-Caltech/Space Science Institute
Cassini looks over the heavily cratered surface of Rhea during the spacecraft's flyby of the moon on March 10, 2012. Image Credit & Copyright: NASA/JPL-Caltech/Space Science Institute
The Discovery of Rhea
Rhea is one of the four moons discovered by Italian astronomer Giovanni Cassini. He spotted the icy moon on Dec. 23, 1672. It was the second moon he observed, and the third to be found in orbit around the ringed planet.
Exploration of Rhea
Several spacecraft have flown by Jupiter and its moons. Pioneer 10 arrived first, in 1973, followed by Pioneer 11 in 1974. Voyager 1 and Voyager 2 returned striking photos during their flybys. The Galileo spacecraft passed as low as 162 miles (261 km) over the surfaces of the Galilean moons and produced detailed images.
Surface features on Rhea -- mostly impact craters in this image -- are thrown into sharp relief thanks to long shadows. Image Credit & Copyright: NASA/JPL-Caltech/Space Science Institute
This cutaway view of Saturn's moon Enceladus is an artist's rendering that depicts possible hydrothermal activity that may be taking place on and under the seafloor of the moon's subsurface ocean, based on recently published results from NASA's Cassini mission. Image Credit & Copyright: NASA/JPL-Caltech
Enceladus' Icy Geysers
At least 70 Yellowstone-like geysers vent icy material from beneath the moon's into space as the moon interacted with its parent planet. Gravitational forces open and close the cracks as Enceladus travels closer to and farther from Saturn over the course of its elliptical 1.37-Earth-day orbit.
Enceladus: The Possibility of Life
Although the freezing moon should be too cold for liquid water, the presence of ammonia in the material streaming from Enceladus could act as antifreeze to keep water beneath the surface from freezing. Cassini detected other complex chemicals and organics in the vaporous plumes, which could make the moon a bright spot in the solar system when it comes to hosting life, making it an excellent target for further exploration.
This picture, an attempt to show how Io would appear in the "true colors" perceptible to the average human eye, was taken in 1999 July by the Galileo spacecraft that orbited Jupiter from 1995 to 2003. Image Credit & Copyright: Galileo Project, JPL, NASA
The Discovery of Titan
The moon was discovered by Dutch astronomer Christiaan Huygens in 1655. The Huygens lander probe sent to the moon aboard NASA's Cassini spacecraft by the European Space Agency is named in his honor.
Exploration of Titan
The Cassini spacecraft launched in 1997 and carried the Huygens probe built by the European Space Agency. Huygens was equipped to study Titan by landing on the Saturn moon. Cassini arrived in orbit around Saturn in 2004 with the Huygens probe landing via parachute on Jan. 14, 2005. Because of Huygens's observations, Titan became a top priority for scientists. The mission has achieved excellent results, such as taking the highest resolution images ever achieved of this moon´s surface.The focus of the mission, as it relates to Titan, is to find signs of seasonal changes and volcanic activity.
The Cassini spacecraft looks through Titan's thick atmosphere to reveal bright and dark terrains on the Saturn-facing side of the planet's largest moon. North is up. Image Credit & Copyright: NASA/JPL/Space Science Institute
The Discovery of Enceladus
When Sir William Herschel turned his 1.2-meter telescope toward the sky for its first observation on Aug. 28, 1789, the new instrument proved its worth by aiding him in the discovery of a new moon around the ringed planet, Saturn. Enceladus would be the first of two moons discovered by Herschel, and the sixth moon found orbiting Saturn.
Exploration of Enceladus
Scientists are developing a mission concept that would snag icy particles from Saturn's moon Enceladus and return them to Earth, where they could be analyzed for signs of life.
The spacecraft would fly through the icy plume blasted into space bygeysers near Enceladus' south pole, then send the collected particles back to our planet in a return capsule.
At least four distinct plumes of water ice spew out from the south polar region of Saturn's moon Enceladus in this dramatically illuminated image. Image Credit & Copyright: NASA/JPL/Space Science Institute
These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn's moon Titan. The views, taken during three different Cassini flybys of Titan, show that this feature was not visible in earlier radar images of the same region and its appearance changed between 2013 and 2014.
Image Credit & Copyright: NASA/JPL-Caltech/ASI/Cornell