Cassini spacecraft image: Saturn's moons Tethys, Hyperion and Prometheus

The Cassini spacecraft captures a rare family photo of three of Saturn's moons that couldn't be more different from each other!

As the largest of the three, Tethys (image center) is round and has a variety of terrains across its surface.

Meanwhile, Hyperion (to the upper-left of Tethys) is the "wild one" with a chaotic spin and Prometheus (lower-left) is a tiny moon that busies itself sculpting the F ring.

To learn more about the surface of Tethys (660 miles, or 1,062 kilometers across), see PIA17164.

More on the chaotic spin of Hyperion (168 miles, or 270 kilometers across) can be found at PIA07683, and discover more about the role of Prometheus (53 miles, or 86 kilometers across) in shaping the F ring in PIA12786.

This view looks toward the sunlit side of the rings from about 1 degree above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 14, 2014.

The view was acquired at a distance of approximately 1.2 million miles (1.9 million kilometers) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 22 degrees.

Image scale is 7 miles (11 kilometers) per pixel.

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.

NASA Cassini Image: Saturn's Moon Tethys in Sunlight

Credit: NASA/JPL-Caltech /Space Science Institute

Tethys, like many moons in the solar system, keeps one face pointed towards the planet around which it orbits.

Tethys' anti-Saturn face is seen here, fully illuminated, basking in sunlight.

On the right side of the moon in this image is the huge crater Odysseus.

The Odysseus crater is 280 miles (450 kilometers) across while Tethys is 660 miles (1,062 kilometers) across.

See PIA07693 for a closer view and more information on the Odysseus crater.

This view looks toward the anti-Saturn side of Tethys.

North on Tethys is up and rotated 33 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 15, 2013.

The view was acquired at a distance of approximately 503,000 miles (809,000 kilometers) from Tethys. Image scale is 3 miles (5 kilometers) per pixel.

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.

NASA Cassini: Saturn's moons - Tiny Tethys

Image credit: NASA/JPL-Caltech/Space Science Institute

Tethys may not be tiny by normal standards, but when it is captured alongside Saturn, it can't help but seem pretty small.

Even Saturn's rings appear to dwarf Tethys (660 miles, or 1,062 kilometers across), which is in the upper left of the image, although scientists believe the moon to be many times more massive than the entire ring system combined.

This view looks toward the unilluminated side of the rings from about 18 degrees below the ringplane.

The image was taken in green light with the Cassini spacecraft wide-angle camera on Aug. 19, 2012.

The view was acquired at a distance of approximately 1.5 million miles (2.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 63 degrees. Image scale is 86 miles (138 kilometers) per pixel.

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.

Saturn's moons Mimas and Tethys bear 'Pac-Man' signatures

Saturn's moons Mimas (left) and Tethys are now both known to exhibit the curious temperature patterns.

Astronomers have seen that the temperature of Saturn's moon Tethys has hotter regions uncannily like the 1980s arcade game character Pac-Man.

A similar feature was spotted in 2010 on Mimas, another Saturnian moon.

A report in Icarus suggests the effect is due to high-energy electrons bombarding the sides of the moons that face their direction of orbital travel.

That compacts the surfaces to a hard, icy texture that does not heat or cool as rapidly as the unaffected surface.

Thermal images of both moons were obtained by the Cassini-Huygens mission, launched in 1997 to study the Saturn system in detail.

The temperatures seen by the spacecraft are distinctly chilly - the warmest parts of Tethys were at - 183C, but inside the "mouth" of the Pac-Man shape it was 15C cooler still.

At the time of the finding of the first Pac-Man shape on Mimas, scientists were unsure what might be the cause, theorising that differing surface textures probably played a role.

The existence of another such shape nearby has cemented the idea that fast-moving electrons are responsible.

"Finding a second Pac-Man in the Saturn system tells us that the processes creating these 'Pac-Men' are more widespread than previously thought," said Carly Howett, of the Southwest Research Institute in Texas and lead author of the study.

"The Saturn system - and even the Jupiter system - could turn out to be a veritable arcade of these characters," she said.

NASA Cassini Image: Saturn's Moons - Giant Titan and tiny Tethys

The Cassini spacecraft watches a pair of Saturn's moons, showing the hazy orb of giant Titan beyond smaller Tethys. 

This view looks toward the Saturn-facing sides of Titan (3,200 miles, or 5,150 kilometers across) and Tethys (660 miles, or 1,062 kilometers across).

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on Oct. 18, 2010. 

The view was obtained at a distance of approximately 1.6 million miles (2.5 million kilometers) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 55 degrees. 

The view was obtained at a distance of approximately 930,000 miles (1.5 million kilometers) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 55 degrees. 

Image scale is 15 kilometers (9 miles) per pixel on Titan and 6 miles (9 kilometers) per pixel on Tethys.

Image Credit: NASA/JPL/Space Science Institute