Busy Moon

Half an hour after Prometheus tore into Saturn's F ring, Cassini snapped this image just as the moon was creating a new streamer in the ring. The dark pattern shaped like an upside down check mark in the lower left of the image is Prometheus and its shadow. The potato shaped moon can just be seen coming back out of the ring.

The moon’s handiwork also is apparent in two previous streamer-channel formations on the right of the image. The darkest streamer-channel stretching from the top right to the center of the image shows Prometheus’ previous apoapse passage about 15 hours earlier. A fainter, even earlier channel extends to the edge of the image.

Prometheus (86 kilometers, 53 miles across) dips into the inner edge of the F ring when it reaches apoapse, its farthest point from Saturn. At apoapse, the moon’s gravity pulls out particles of the ring into a streamer. As Prometheus moves back toward periapse -- its orbit's closest point to the planet -- the streamer gets longer. Then, as Prometheus moves back toward apoapse, the streamer breaks apart which results in a dark channel. This streamer-channel cycle repeats once every orbit with the streamer-channel features being streamers during Prometheus periapse and channels during Prometheus apoapse.

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grooves on blue

Cassini peers through Saturn's delicate, translucent inner C ring to see the diffuse blue limb of Saturn's atmosphere. This view looks toward the unilluminated side of the rings from about 20 degrees above the ringplane. 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 April 25, 2008 at a distance of approximately 1.5 million kilometers (913,000 miles) from Saturn. Image scale is 8 kilometers (5 miles) per pixel. Image scale is 8 kilometers (5 miles) per pixel.

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static world

Saturn's ragged moon Rhea has one of the oldest surfaces known. Estimated as changing little in the past billion years, Rhea shows craters so old they no longer appear round – their edges have become compromised by more recent cratering. Like Earth's Moon, Rhea's rotation is locked on Saturn, and the above image shows part of Rhea's surface that always faces Saturn. Rhea's leading surface is more highly cratered than its trailing surface. Rhea is composed mostly of water-ice but is thought to include about 25 percent rock and metal. The above image was taken by the robot Cassini spacecraft now orbiting Saturn. Cassini swooped past Rhea last month and captured the above image from about 350,000 kilometers away. Rhea spans 1,500 kilometers making it Saturn's second largest moon after Titan. Several surface features on Rhea remain unexplained including large light patches like those seen near the image top.

stripes and holes

The tiger stripes on Saturn's moon Enceladus might be active. Even today, they may be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Recent evidence for this has come from the robot Cassini spacecraft now orbiting Saturn. Cassini detected a marked increase in particle collisions during its July flyby only 270 kilometers over a South Polar region of Enceladus. Pictured above, a high resolution image of Enceladus is shown from the close flyby. The unusual surface features dubbed tiger stripes are visible on the left in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead.

all mighty saturn

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photo session: titan

titan and rhea

saturn/sun eclipse from titan

titan and saturn's rings

the majestic giant planet and his rings

Saturn never shows a crescent phase -- from Earth. But when viewed from beyond, the majestic giant planet can show an unfamiliar diminutive silver. This image of crescent Saturn in natural color was taken by the robotic Cassini spacecraft in May. The image captures Saturn's majestic rings from the side of the ring plane opposite the Sun -- the unilluminated side -- another vista not visible from Earth. Pictured are many of Saturn's photogenic wonders, including the subtle colors of cloud bands, the complex shadows of the rings on the planet, the shadow of the planet on the rings, and the moons Mimas (2 o'clock), Janus (4 o'clock), and Pandora (8 o'clock). As Saturn moves towards equinox in 2009, the ring shadows are becoming smaller and moving toward the equator. During equinox, the rings will be nearly invisible from Earth and project only an extremely thin shadow line onto the planet.

iapetus

Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

What does the surface of Saturn's mysterious moon Iapetus look like? To help find out, the robotic Cassini spacecraft now orbiting Saturn was sent soaring last week just 2,000 kilometers from the unique equatorial ridge of the unusual walnut-shaped two-toned moon. The above image from Cassini is from about 4,000 kilometers out and allows objects under 100-meters across to be resolved. Cassini found an ancient and battered landscape of craters, sloping hills, and mountains as high as 10 kilometers and so rival the 8.8-kilometer height of Mt. Everest on Earth. Just above the center of this image is a small bright patch where an impacting rock might have uncovered deep clean water ice. Space scientists will be studying flyby images like this for clues to the origin of Iapetus' unusual shape and coloring with particular emphasis because no more close flybys of the enigmatic world are planned.

Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

photo session: saturn

Four million miles (6,400,000 kilometers) from Saturn in late 2004, the Cassini spacecraft snapped a series of 126 natural-color photographs—the most detailed portrait of the planet ever made. Cassini, which began its voyage in 1997, is one of the most ambitious missions to another planet.

Hyperion

Despite its bathtub-ready appearance, Hyperion—Saturn's largest irregularly shaped moon—is anything but spongy.
High-resolution images taken by NASA's Cassini spacecraft—including the picture above taken in 2005—suggest the satellite's cuplike craters are reservoirs for hydrocarbons. The finding could mean that the ingredients needed for life as we know it may be more common in our solar system than previously thought, according to NASA.
Dark material spotted at the bottoms of some of the moon's craters has the same chemical signature as hydrocarbons, NASA scientists said. These organic molecules—made of hydrogen and carbon—are also found in comets, meteorites, and galactic dust.

eclipsed saturn

Saturn eclipsing the sun, seen from behind from the Cassini orbiter. The image is a composite assembled from images taken by the Cassini spacecraft on 15 September, 2006.

Individual rings seen include (in order, starting from most distant):
- E ring
- Pallene ring (visible very faintly in an arc just below Saturn)
- G ring
- Janus/Epimetheus ring (faint)
- F ring (narrow brightest feature)
- Main rings (A,B,C)
- D ring (bluish, nearest Saturn)

For a detailed description, see http://photojournal.jpl.nasa.gov/catalog/PIA08329 and http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=698

largest known star

VY Canis Majoris (VY CMa) is a red hypergiant located in the constellation of Canis Major. This is the largest known star and one of the most luminous stars known.

Roberta M. Humphreys (2006) estimates the radius of VY CMa is between 1800 and 2100 solar radii. If our sun were replaced with such a star, its surface could extend to the orbit of Saturn. If we take its radius to be that higher figure of 2100 solar radii, it would take more than 8 hours for light to travel around its circumference. If it were possible for a human to walk on the surface of Canis Majoris, at 3 miles an hour for 8 hours a day, it would take him or her 650,000 years to walk the entire circumference (compared with 2 years 11 months to complete the same task on the Earth).

Object Name:
VY Canis Majoris
Object Description:
Variable Star with Circumstellar Nebula
Position (J2000):
R.A. 07h 22m 58s.33Dec. -25° 46' 3".2
Constellation:
Canis Major
Distance:
Approximately 5,000 light-years (1.5 kiloparsecs)
Dimensions:
These images are roughly 35 arcseconds (0.85 light-years or 0.25 parsecs) across.

VY Canis Majoris Credit: NASA, ESA, and R. Humphreys (University of Minnesota)

Descent Panorama of Saturn's Titan

Credit: ESA, NASA, Descent Imager/Spectral Radiometer Team (LPL)

You're the first spacecraft ever to descend to Titan -- what do you see? Immediately after the Huygen's probe pierced the cloud deck of Saturn's moon Titan last January, it took a unique series of pictures of one of the Solar System's most mysterious moon's. Those pictures have recently been digitally stitched together to create spectacular panoramas and a dramatic descent movie. Pictured above is a panoramic fisheye view Huygen's obtained from about five kilometers above Titan's surface. The digital projection makes the local surface, mostly flat, appear as a ball, but allows one to see in all directions. Huygen's eventual landing site was in the large dark area below, just right of the center. This relatively featureless, dark, sandy basin appears to be surrounded by light colored hills to the right and a landscape fractured by streambeds and canyons above. Recent evidence indicates that Titan's lakebeds and streambeds are usually dry but sometimes filled with a flashflood of liquid methane from rare torrents of methane rain.

eclipse

Credit: Mir 27 Crew; Copyright: CNES

Here is what the Earth looks like during a solar eclipse. The shadow of the Moon can be seen darkening part of Earth. This shadow moved across the Earth at nearly 2000 kilometers per hour. Only observers near the center of the dark circle see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon. This spectacular picture of the 1999 August 11 solar eclipse was one of the last ever taken from the Mir space station. The two bright spots that appear on the upper left are possibly Jupiter and Saturn, although this has yet to be proven. Mir was deorbited in a controlled re-entry in 2001.

(from: Astronomy picture of the day)