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Views of Moons

NASA’S CASSINI SPACECRAFT, in orbit around the planet Saturn, has been sending back some wonderful views of its moons. In particular, it has captured images where one moon seems to float in front of the other. Here we present a selection of recent images.

Cassini image of Titan and Tethys

Can you tell which of these moons in the foreground? It's Titan, the large one (diameter 5,150 kilometres; bigger than our Moon) with the orange atmosphere, with smaller, shiny, icy Tethys in the background. Titan was 2.3 million kilometres from Titan, and 3.4 million from Tethys when it took this image. Saturn's rings can be seen edge-on in the distance.

Cassini image of Rhea and Titan

This black-and-white image shows the moon Rhea (1,528 km diameter) in front of Titan. Cassini was 2 million kilometres from Titan and 1.3 million kilometres from Rhea when it took this image.

Cassini image of Titan and Dione

This view shows Titan again, this time with the much smaller moon Dione (1,123 km diameter) peering around from behind, with Saturn and its rings (edge-on) in the background. Cassini was 2.3 million kilometres from Titan and 3.2 million kilometres from Dione when it took the image. The haze that surrounds Titan can clearly be seen. Titan has a mostly nitrogen atmosphere that extends far from the surface. The surface pressure is about 1.5 times that on Earth.

Cassini image of Titan

In this view, Titan appears to float in front of Saturn and its rings. Titan is not only the second-largest moon in the Solar System; it's also about 300 kilometres wider than the planet Mercury!

More information: Cassini mission

Story by Jonathan Nally. Images courtesy NASA / JPL-Caltech / Space Science Institute.

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Gallery – Geyser moon seen in silhouette

Saturn's moon Enceladus

Saturn's moon Enceladus appears in silhouette in this image taken by NASA's Cassini spacecraft. The bulk of Saturn is in the background, the planet's rings seen edge-on appear as the dark horizontal line.

NASA’S CASSINI SPACECRAFT took this image of Saturn’s moon Enceladus on October 19, 2011. As the spacecraft passed Enceladus, its infrared instruments, cameras and other instruments monitored activity on the moon, in particular the famed jets erupting from the its south pole. The orbiter flew within about 1,230 kilometres of Enceladus’ surface.

Although it appears dark in the silhouetted view, Enceladus, 504 kilometres wide, is actually one of the most reflective bodies in the Solar System because it is constantly coated by fresh, white particles of ice.

Also visible are Saturn’s rings, seen edge on.

More information:

Enceladus – Saturn’s shiny moon

The eruptions of Enceladus

Adapted from information issued by NASA/JPL-Caltech/Space Science Institute.

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Gallery – Quintet of Saturnian moons

Five of Saturn's moons

Five of Saturn's moons can be seen in this image taken by NASA's Cassini spacecraft.

A QUINTET OF SATURN’S MOONS can be seen in this view taken by the Cassini spacecraft.

Janus (179 kilometres wide) is on the far left. Pandora (81 kilometres) orbits between the A ring and the thin F ring near the middle of the image. Brightly reflective Enceladus (504 kilometres) appears above the centre of the image. Saturn’s second largest moon, Rhea (1,528 kilometres), is bisected by the right edge of the image. The smaller moon Mimas (396 kilometres) can be seen beyond Rhea also on the right side of the image.

This view looks toward the northern, sunlit side of the rings from just above the ringplane. Rhea is closest to the camera. Saturn’s rings are beyond Rhea and Mimas. Enceladus also is beyond the rings.

The image was taken with the Cassini spacecraft narrow-angle camera on July 29, 2011. The view was acquired at a distance of approximately 1.1 million kilometres from Rhea and 1.8 million kilometres from Enceladus.

Adapted from information issued by NASA / JPL-Caltech / Space Science Institute.

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Gallery – Dione and friends

Saturn's moon Dione

Saturn's moon Dione, seen along with half of Saturn and the planets rings.

SATURN’S MOON DIONE coasts along in its orbit appearing in front of its parent planet in this Cassini spacecraft view.

The wispy terrain on the trailing hemisphere of Dione (1,123 kilometres wide) can be seen on the left of the moon here.

Dione (pronounced dy-OH-nee) is the second densest moon of Saturn, after Titan. Dione is probably composed of a rocky core making up one-third of the moon’s mass, and the rest is composed of water ice. It is similar to two other Saturnian moons, Tethys and Rhea.

Dione’s icy surface includes heavily cratered terrain, with moderately and lightly cratered plains, as well as some severely cracked areas, with very bright material on the walls of the fractures. The heavily cratered terrain has numerous craters greater than 100 kilometres in diameter. The plains area tends to have craters less than 30 kilometres in diameter.

Telesto and Epimetheus

The moon Telesto can be seen above the rings on the left, and Epimetheus is just on the bottom edge of the rings.

The tiny moon Telesto (25 kilometres wide) is visible as a white speck above and to the left of the rings in this view. Epimetheus (113 kilometres) appears just below the rings near the centre of the image. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken with the Cassini spacecraft narrow-angle camera on July 18, 2011. The view was acquired at a distance of approximately 2.2 million kilometres from Dione.

Adapted from information issued by NASA / JPL-Caltech / Space Science Institute.

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Gallery – Saturn’s four moon shuffle

Cassini image of four Saturnian moons

Four of Saturn's moons are visible in the image taken by NASA's Cassini spacecraft.

A QUARTET OF SATURN’S MOONS, from tiny to huge, surround and are embedded within the planet’s rings in this Cassini image. Saturn itself is out of frame to the left.

Saturn’s largest moon, Titan (5,150 kilometres wide), is in the background of the image.

Next, in the foreground is Dione (1,123 kilometres wide), with the wispy terrain on its trailing hemisphere easily visible.

The third moon is Pandora(81 kilometres wide), which orbits just beyond the rings on the right of the image.

Saturn's rings with Pan in the  Encke gap

The tiny moon Pan appears as a speck in the gap in the rings.

Finally, tiny Pan (28 kilometres wide) can just be seen as a tiny speck in the ‘Encke Gap’ of the A ring on the left of the image.

Saturn has 62 known moons, with the vast majority of them being 50 kilometres or less in diameter.

The image was taken with the Cassini spacecraft narrow-angle camera on September 17, 2011, at a distance of approximately 2.1 million kilometres from Dione.

Adapted from information issued by NASA / JPL-Caltech / Space Science Institute.

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Trio of Saturnian moons

Three of Saturn's moons

Three of Saturn's moons captured by NASA's Cassini spacecraft. From left: Dione, Rhea and Enceladus.

NASA’S CASSINI SPACECRAFT snapped this image of three of Saturn’s moons and part of the planet’s rings.

Saturn is not illuminated in this image, but it can be detected as the dark patch on the left that lies behind the foreground rings but in front of the background rings. It also partially obscures the moon on the left.

That moon is Dione (1,123 kilometres wide), around 3.1 million kilometres from Cassini when this image was taken.

In the foreground is Rhea (1,528 km wide). It is closest to the camera, at a distance of about 2.2 million kilometres.

The third moon, on the right, is Enceladus (504 km wide), seen at a distance of about 3 million kilometres.

Enceladus is the source of much interest at the moment, as Cassini’s instruments have detected huge plumes of salty spray shooting up from cracks near it’s south pole, suggesting a liquid ocean lies beneath the frozen surface.

More information:

Cassini-Huygens mission

Cassini imaging team homepage

Story by Jonathan Nally, SpaceInfo.com.au. Images courtesy NASA / JPL / Space Science Institute.

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Up close with Helene

Cassini image of Helene

Saturn's icy moon Helene, seen by the Cassini spacecraft from a distance of 6,968 kilometres. Detail can be seen down to 42 metres per pixel.

NASA’s CASSINI SPACECRAFT has successfully completed its second-closest encounter with Saturn’s icy satellite Helene, beaming down raw images of the small moon.

At closest approach, on June 18, Cassini flew within 6,968 kilometres of Helene’s surface. It was the second closest approach to Helene of the entire mission.

Cassini passed from Helene’s night side to the moon’s sunlit side. It also captured images of the Saturn-facing side of the moon in sunlight, a region that was only illuminated by sunlight reflected off Saturn the last time Cassini was close, in March 2010.

The data from this flyby will enable scientists to finish creating a global map of Helene, so they can better understand the history of impacts to the moon and gully-like features seen on previous flybys.

Helene is potato shaped, with dimensions of 36 x 32 x 30 kilometres. It was discovered in 1980 by astronomers at the Pic du Midi Observatory in France.

The closest Helene encounter of the mission took place on March 10, 2010, when Cassini flew within 1,820 kilometres of the moon.

Cassini image of Helene

Another Cassini view of Helene, captured on June 18, 2011.

Adapted from information issued by NASA / JPL-Caltech / Space Science Institute.

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One image, five moons

Five of Saturn's moons in one image

Five of Saturn's moons appear in this single image taken by NASA's Cassini spacecraft.

NASA’s CASSINI SPACECRAFT snapped this image showing part of Saturn’s rings edge-on, and with five of the giant planet’s moons in the same frame.

The moon Rhea (1,528 kilometres in diameter) dominates the image, and is in the foreground of the tableau. Below it and appearing to sit on the rings, is Dione (1,123km wide). Dione is actually far in the background.

Just to the right of Dione is what looks like a small bump in the rings. This is actually Prometheus (86km wide), a “shepherd moon” that orbits Saturn along the inner edge of the F ring.

The tiny dot off to the right of the rings is Epimetheus (113km wide), and the larger moon right on the edge of the image is Tethys (1,062km wide). Epimetheus is very interesting, as it shares almost exactly the same orbit as another moon, Janus. In fact, their orbits are different by a factor of only 50 kilometres. And every now and then they come close together and swap positions!

Cassini was about 61,000 kilometres from Rhea when it took this image on January 11, 2011. Detail can be seen on Rhea down to about 2km per pixel.

Just so that you know what each of the moons looks like close up, here are images of them, also taken by Cassini.

Saturn's moon Rhea.

Saturn's moon Rhea.

Saturn's moon Dione.

Saturn's moon Dione.

Saturn's moon Prometheus.

Saturn's moon Prometheus.

Saturn's moon Epimetheus.

Saturn's moon Epimetheus.

Saturn's moon Tethys.

Saturn's moon Tethys.

Adapted from information issued by NASA/JPL/Space Science Institute.

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Saturn’s three-in-one

Image showing Rhea, Dione and Saturn's rings

This image shows two of Saturn's moons—Rhea (foreground, top) and Dione (background)—with the planet's famous rings in between.

THIS IMAGE ISN’T made up. It’s a real shot from NASA’s Cassini spacecraft, showing three components of the Saturnian system in the one frame.

In the foreground at top is the south polar area of Saturn’s moon Rhea. In the background is another moon, Dione, with Saturn’s almost edge-on rings in between.

Visible on Dione is its famous light-coloured ‘wispy’ terrain.

Rhea is 1,528 kilometres in diameter, and Dione is 1,123 kilometres wide.

At the moment the image was taken, on January 11, 2011, the Cassini spacecraft was about 61,000 kilometres from Rhea and 924,000 kilometres from Dione.

Detail down to a resolution of 358 is visible on Rhea, and to a resolution of six kilometres on Dione.

Story copyright 2011 Jonathan Nally, SpaceInfo.com.au. Image courtesy NASA / JPL / Space Science Institute.

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Enceladus – Saturn’s shiny moon

Saturn's moon Enceladus

Saturn's moon Enceladus is kept looking young by a fresh coating of fine, white icy particles. This Cassini spacecraft image taken from a distance of 102,000km.

SATURN’S MOON ENCELADUS reflects sunlight brightly while the planet and its rings fill the background, in this image (above) taken by NASA’s Cassini spacecraft.

Enceladus, 504 kilometres wide, is one of the most reflective bodies in the Solar System because it is constantly coated by fresh, white ice particles.

The view was obtained at a distance of approximately 102,000 kilometres from Enceladus, giving an image resolution of 612 metres per pixel.

In an image from a different angle (below), Cassini looked over cratered and tectonically deformed terrain on Enceladus as the camera also caught a glimpse of Saturn’s rings in the background. The image was taken during the spacecraft’s flyby of Enceladus on November 30, 2010.

Saturn's moon Enceladus

Saturn's rings form the backdrop to this Cassini view of Enceladus, taken from a distance of 46,000km.

Geologically young terrain in the middle latitudes of the moon gives way to older, cratered terrain in the northern latitudes.

The view was acquired at a distance of approximately 46,000 kilometres from Enceladus, giving an image scale of 276 metres per pixel.

Adapted from information issued by NASA / JPL / Space Science Institute.

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