March 7, 2005

Volunteer Network Provides Ringside Seat to Saturn
Experiencing Saturn through a telescope for the first time is a feast for the eyes. NASA's Cassini mission to Saturn is helping people savor the view by coordinating a network of people and telescopes around the globe to help others see the ringed giant. The Cassini Saturn Observation Campaign includes more than 380 volunteers located in 44 U.S. states and 50 countries. During the past year, Saturn Observation Campaign members held nearly 800 events for more than 108,000 people from all ages and walks of life, including students, teachers and curious members of the public...

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me@rescam.org

heh heh Thierry you got my threads mixed up. :)

Glacial, volcanic and fluvial activity on Mars: latest images

25 February 2005

New images, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, were released at the First Mars Express Science Conference this week. They show the areas of focused research - water, ice, glaciers and volcanism.

The Greatest Saturn Portrait...Yet

February 25, 2005

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While cruising around Saturn in early October, Cassini captured a series of images that have been composed into the largest, most detailed, global natural color view of Saturn and its rings ever made.

This grand mosaic consists of 126 images acquired in a tile-like fashion, covering one end of Saturn's rings to the other and the entire planet in between. The images were taken over the course of 2 hours on October 6, 2004, while Cassini was approximately 6.3 million kilometers (3.9 million miles) from Saturn. Since the view seen by Cassini during this time changed very little, no re-projection or alteration of any of the images was necessary.

Three images (red, green and blue) were taken at each of 42 locations, or “footprints”, across the planet. The full color footprints were mosaicked together to produce a final product that is 8,888 pixels across and 4,544 pixels tall.

The smallest features seen here are 38 kilometers (24 miles) across. Many of Saturn's splendid features noted previously in single frames taken by Cassini are visible in this one detailed, all-encompassing view: Subtle color variations across the rings, the thread-like F ring, ring shadows cast against the blue northern hemisphere, the planet’s shadow making its way across the rings to the left, blue-grey storms in Saturn's southern hemisphere to the right and tiny Mimas and even smaller Janus (both faintly visible at lower left).

The Sun-Saturn-Cassini, or phase, angle at the time was 72 degrees; hence, the partial illumination of Saturn in this portrait. Later in the mission, when the spacecraft’s trajectory takes it far from Saturn and also into the direction of the Sun, Cassini will be able to look back and view Saturn and its rings in a more fully-illuminated geometry.

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February 24, 2005

The Dragon Storm

A large, bright and complex convective storm that appeared in Saturn's southern hemisphere in mid-September 2004 was the key in solving a long-standing mystery about the ringed planet.
Saturn's atmosphere and its rings are shown here in a false color composite made from Cassini images taken in near infrared light through filters that sense different amounts of methane gas. Portions of the atmosphere with a large abundance of methane above the clouds are red, indicating clouds that are deep in the atmosphere. Grey indicates high clouds, and brown indicates clouds at intermediate altitudes. The rings are bright blue because there is no methane gas between the ring particles and the camera.

The complex feature with arms and secondary extensions just above and to the right of center is called the Dragon Storm. It lies in a region of the southern hemisphere referred to as "storm alley" by imaging scientists because of the high level of storm activity observed there by Cassini in the last year.

The Dragon Storm was a powerful source of radio emissions during July and September of 2004. The radio waves from the storm resemble the short bursts of static generated by lightning on Earth. Cassini detected the bursts only when the storm was rising over the horizon on the night side of the planet as seen from the spacecraft; the bursts stopped when the storm moved into sunlight. This on/off pattern repeated for many Saturn rotations over a period of several weeks, and it was the clock-like repeatability that indicated the storm and the radio bursts are related. Scientists have concluded that the Dragon Storm is a giant thunderstorm whose precipitation generates electricity as it does on Earth. The storm may be deriving its energy from Saturn's deep atmosphere.

One mystery is why the radio bursts start while the Dragon Storm is below the horizon on the night side and end when the storm is on the day side, still in full view of the Cassini spacecraft. A possible explanation is that the lightning source lies to the east of the visible cloud, perhaps because it is deeper where the currents are eastward relative to those at cloud top levels. If this were the case, the lightning source would come up over the night side horizon and would sink down below the day side horizon before the visible cloud. This would explain the timing of the visible storm relative to the radio bursts.

The Dragon Storm is of great interest for another reason. In examining images taken of Saturn's atmosphere over many months, imaging scientists found that the Dragon Storm arose in the same part of Saturn's atmosphere that had earlier produced large bright convective storms. In other words, the Dragon Storm appears to be a long-lived storm deep in the atmosphere that periodically flares up to produce dramatic bright white plumes which subside over time. One earlier sighting, in July 2004, was also associated with strong radio bursts. And another, observed in March 2004 and captured in a movie created from images of the atmosphere (http://photojournal.jpl.nasa.gov/catalog/PIA06082 and http://photojournal.jpl.nasa.gov/catalog/PIA06083) spawned three little dark oval storms that broke off from the arms of the main storm. Two of these subsequently merged with each other; the current to the north carried the third one off to the west, and Cassini lost track of it. Small dark storms like these generally get stretched out until they merge with the opposing currents to the north and south.

These little storms are the food that sustains the larger atmospheric features, including the larger ovals and the eastward and westward currents. If the little storms come from the giant thunderstorms, then together they form a food chain that harvests the energy of the deep atmosphere and helps maintain the powerful currents.

Cassini has many more chances to observe future flare-ups of the Dragon Storm, and others like it over the course of the mission. It is likely that scientists will come to solve the mystery of the radio bursts and observe storm creation and merging in the next 2 or 3 years.

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me@rescam.org

February 24, 2005

Cassini Continues Making New Saturn Discoveries
NASA's Cassini spacecraft continues making new and exciting discoveries. New findings include wandering and rubble-pile moons; new and clumpy Saturn rings; splintering storms and a dynamic magnetosphere...

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me@rescam.org

February 22, 2005

Slice of Tethys
This Cassini view of Saturn's moon Tethys shows several large craters near the moon's eastern limb. These craters have fanciful names such as Phemius, Polyphemus and Ajax. The moon's massive rift-like canyon system, Ithaca Chasma, is in the darkness to the west. Tethys is 1,071 kilometers (665 miles) across. The image has been rotated so that north on Tethys is up. This view shows mainly the moon's trailing hemisphere. The image was taken in visible blue light with the Cassini spacecraft narrow angle camera on Jan. 19, 2005, at a distance of approximately 1.9 million kilometers (1.2 million miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 111 degrees. Resolution in the original image was 11 kilometers (7 miles) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility.

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me@rescam.org

February 21, 2005

3D Clouds
Clouds near the boundary of day and night on Saturn show unusual three-dimensional structure in this Cassini view. At this location on the planet, the Sun is at a very low angle, causing vertical relief to become apparent. Generally, Cassini imaging scientists use specially designed spectral filters to probe the vertical structure of the gas giant's atmosphere. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 16, 2005, at a distance of approximately 2.8 million kilometers (1.7 million miles) from Saturn. North is to the upper right. The image scale is 17 kilometers (11 miles) per pixel.

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me@rescam.org

February 18, 2005

False Color Look at Enceladus
A fresh look at Enceladus (505 kilometers, 314 miles across) reveals tempting new details about the brightest real estate in the Solar System. This falsely-colored image shows that some of the linear features on Enceladus have a slightly different color from their surroundings. Different colors of ice may be caused by different compositions or different ice crystal sizes, either of which can indicate different formation mechanisms or different ages. The new view shows some of the smooth plains noted in Voyager and earlier Cassini images. At about the 7 o’clock position are interwoven lineament patterns that are reminiscent of the wispy-terrain features on Dione and Rhea. Imaging scientists are unsure as to whether these brighter markings are evidence for contamination of the ice in the linear features by some other material. Analysis of high resolution images of Enceladus should also show whether, like the surprising terrain seen on Dione, the "wisps" are curvilinear fractures that are not quite resolved at this scale. This false color view combines images obtained using filters sensitive to polarized green and infrared light. The images were obtained with the narrow angle camera on February 16, 2005, from distances ranging from 179,727 to 179,601 kilometers (111,677 to 111,599 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 22 degrees. Resolution in the image is about 1 kilometer (0.6 mile) per pixel. For more pictures of Enceladus visit http://ciclops.lpl.arizona.edu/view_event.php?id=11

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me@rescam.org

February 18, 2005

Saturn's Moons Titan and Enceladus Seen by Cassini
NASA's Cassini spacecraft has had a busy week, snapping stunning new images of two of Saturn's moons -- smoggy Titan on Feb. 15 and wrinkled Enceladus on Feb. 16. Visible in radar images released today are a crater, channels, and terrain similar to the area where the European Space Agency's Huygens probe landed on Jan. 14...

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me@rescam.org

February 18, 2005

String of Moons?
Three of Saturn's moons appear almost like a string of pearls in this Cassini image, but looks are deceiving. Moons visible in this image: Mimas (398 kilometers, or 247 miles across) at right, Pandora (84 kilometers, or 52 miles across) near center and Janus (181 kilometers, or 113 miles across) in the lower left corner. Mimas' orbit inclination of 1.6 degrees relative to Saturn's equator is enough to make it appear as if it orbits just beyond the F ring when viewed from this vantage point of 5 degrees below the rings. In fact, it is 34,000 kilometers (21,000 miles) more distant than Janus. Contrast in the image was enhanced to make visible the faces of moons lit by reflected light from Saturn (their left sides). Notable here is the irregular shape of Janus, compared with larger, spherical Mimas. The bright B ring (at upper left) appears overexposed due to the extreme contrast enhancement. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 22, 2005, at a distance of approximately 2.7 million kilometers (1.7 million miles) from Saturn. The image scale is 16 kilometers (10 miles) per pixel.

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me@rescam.org

February 17, 2005

Irregular Pair
The oddball shapes of Saturn's small ring moons Prometheus and Epimetheus are discernible in the view from Cassini. Saturn's shadow carves a dark, diagonal swath across the ring plane, even occulting the outer edge of thin, knotted F ring. Prometheus is 102 kilometers, or 63 miles across, while Epimetheus is 116 kilometers, or 72 miles across. Prometheus is visible inside the F ring near center, and Epimetheus is seen near the lower right corner. North on Saturn is to the upper right. The view is from beneath the ring plane. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 22, 2005, at a distance of approximately 2.6 million kilometers (1.6 million miles) from Saturn. The image scale is 15 kilometers (9 miles) per pixel.

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me@rescam.org

February 16, 2005

Cat Scratches
This image is a portion of the swath acquired by the Cassini Titan radar mapper on Feb. 15, 2005, on the mission's second opportunity to image the surface with radar. The frame, measuring about 300 kilometers (186 miles) from top to bottom, shows an area near the northeast corner of the large optically bright region named Xanadu. Running across the image are a series of roughly parallel, mostly east-west dark linear features that join and separate, which are not seen in the previous radar images. They may be formed by the action of eastward-flowing winds, or geologic processes acting on the crust itself. In places they cut through adjacent terrain, while elsewhere the lineaments seem to be interrupted by brighter material, appearing again on the other side. Seams between radar segments are visible as horizontal, sawtooth-shaped lines. Bright material in radar images may be rough or sloped toward the radar (which is observing from the top in this frame). Also, some of what is seen may in fact be below the surface, revealed as the radio waves penetrate overlying, radar-transparent material.

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me@rescam.org

February 16, 2005

Circus Maximus
A huge annular feature with an outer diameter of approximately 440 kilometers (273 miles) appears in this image taken with Cassini's Titan radar mapper. It resembles a large crater or part of a ringed basin, either of which could be formed when a comet or asteroid tens of kilometers in size slammed into Titan. This is the first impact feature identified in radar images of Titan. The surface of Titan appears to be very young compared to other Saturnian satellites. In Titan's case, debris raining down from the atmosphere or other geologic processes may mask or remove the craters. The pattern of brightness suggests that there is topography associated with this feature; for example, in the center of the image there appear to be mounds each about 25 kilometers (15 miles) across. Since they are dark on their lower edges that face away from the radar and bright on the opposite face, they must be elevated above the surrounding terrain. This image is a part of a larger swath acquired on Feb. 15, 2005, on Cassini's second opportunity to map Titan's surface via radar. Seams between radar segments are visible as horizontal, sawtooth-shaped lines.

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me@rescam.org

February 16, 2005

Saturn's Auroras
These images of Saturn's polar aurora were taken by NASA's Hubble Space Telescope on Jan. 24, 26, and 28. Each of the three images of Saturn combines ultraviolet images of the south polar region (to show the auroral emissions) with visible wavelength images of the planet and rings. The Hubble images were obtained during a joint campaign with NASA's Cassini spacecraft to measure the solar wind approaching Saturn and the Saturn kilometric radio emissions. The strong brightening of the aurora on January 26 corresponded with the recent arrival of a large disturbance in the solar wind. These results are presented in three papers, which appear in the Feb. 17 issue of the journal Nature.

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me@rescam.org

February 16, 2005

Bound to Saturn
Saturn's complex rings are both an intriguing scientific puzzle and a supreme natural wonder. This view shows, from upper right to lower left, the thin C ring, multi-toned B ring, the dark Cassini Division, the A ring and narrow F ring. At the bottom, Saturn's moon Mimas (398 kilometers, or 247 miles across) orbits about 45,000 kilometers (28,000 miles) beyond the bright core of the F ring. The little moon is heavily cratered and is thought to be largely composed of water ice. The bright speck just outside of (below) the F ring is the shepherd moon Pandora (84 kilometers, or 52 miles across). The image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 19, 2005, at a distance of 1.8 million kilometers (1.1 million miles) from Saturn. The image scale is 11 kilometers (7 miles) per pixel. Pandora was brightened by a factor of seven to aid visibility.

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me@rescam.org

February 15, 2005

Outsider Moon
Reflected light from Saturn dimly illuminates the night side of the cratered moon Mimas in this Cassini image. Above, the outer edges of the planet's main rings show some interesting details. Mimas is 398 kilometers (247 miles) across. Several thin ringlets comprising the F ring are nicely visible here, and the bright core of the ring displays a few twisted knots. Perhaps less noticeable are kinks in one of the thin ringlets of material visible within the Encke Gap near the upper left corner. The outer edge of the A ring appears notably brighter than the ring material on the other side of the narrow Keeler Gap. Finally, numerous gravitational resonances give the A ring a grooved or striped appearance in this view. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 17, 2005, at a distance of approximately 1.2 million kilometers (746,000 miles) from Saturn. The image scale is 7 kilometers (4 miles) per pixel.

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me@rescam.org

Hear the sounds from Huygens' descent to Titan

Scientists have produced an audio soundbite that captures what the Cassini orbiter heard from Huygens as the probe descended on Titan on Jan. 14.

The sounds may not be music to everyone's ears, but they're beautiful, interesting and important to investigators who are reconstructing the probe's exact position and orientation throughout its parachute dive to Titan's surface.

"The minute-long sound file covers about four hours of real time, from when the Huygens probe deployed its main parachute, down to ground impact two-and-a-half hours later, and then for about another hour on the surface," said Ralph D. Lorenz of the University of Arizona.

Greetings from Germany NRW
Ulli S@h Berkeley's Staff Friends Club m7 ©

February 14, 2005

Enceladus First Flyby
This map of the surface of Saturn's moon Enceladus illustrates the regions that will be imaged by Cassini during the spacecraft's first very close flyby of the moon on Feb. 17, 2005. At closest approach, the spacecraft is expected to pass approximately 1,180 kilometers (733 miles) above the moon's surface. Enceladus is 505 kilometers (314 miles) across. The colored lines delineate the regions that will be imaged at differing resolutions. The coverage at spatial resolution better than 200 meters (656 feet) per pixel primarily targets an area previously seen in NASA's Voyager spacecraft images, but at lower resolution (around 1 kilometer or 0.6 miles per pixel). This high resolution coverage also includes areas in the southern latitudes that were not seen at all by Voyager. The primary purpose of this coverage is to provide detailed information about the nature of different terrain types, especially the smooth plains materials, cratered terrains and system of curvilinear fractures that appear to be tectonic in nature. The highest-resolution coverage (i.e. better than 70 meters, or 230 feet per pixel) focuses on the detailed structure of prominent fractures in the smooth plains. Coverage outlined in purple (i.e., resolution better than 1.5 kilometers or 0.9 miles per pixel) includes an area of Enceladus that was seen by Voyager only at very poor spatial resolution (about 6 kilometers or 3.7 miles per pixel). Cassini's resolution will be approximately four times better in this region. The map was made from images obtained by both the Cassini and Voyager spacecraft. The Cassini images used here were acquired on Jan. 15 and 16, 2005.

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February 14, 2005

Titan Flyby Number Four
This map of the surface of Saturn's moon Titan illustrates the regions that will be imaged by Cassini during the spacecraft's fourth (and third very close) flyby of the smoggy moon on Feb. 15, 2005. At closest approach, Cassini is expected to pass approximately 1,580 kilometers (982 miles) above the moon's surface. The colored lines delineate the regions that will be imaged at differing resolutions. The lower resolution imaging sequences (outlined in blue) are designed to study the atmosphere, clouds and surface in a variety of spectral filters. Other areas have been specifically targeted for creation of mosaics based on moderate resolution images of surface features. Two small areas (outlined in yellow) will be seen at high resolution by Cassini's narrow angle camera, and will be jointly covered by the visual and mapping spectrometer experiment. These high resolution targets also overlap areas covered by the Cassini radar altimetry and synthetic aperture radar experiments. The site where the Huygens probe landed in mid-January will be imaged at lower resolution during this flyby and is within the terrain in the extreme western part of the coverage area. The low-resolution imaging coverage will extend farther east than the previous two close flybys in October and December 2004. Some areas covered at moderate resolution during previous flybys have been targeted again to allow Cassini scientists to look for changes. The map shows only brightness variations on Titan's surface (the illumination is such that there are no shadows and no shading due to topographic variations). Previous observations indicate that, due to Titan's thick, hazy atmosphere, the sizes of surface features that can be resolved are a few to five times larger than the actual pixel scale labeled on the map. The map was made from global images taken in June 2004, at image scales of 35 to 88 kilometers (22 to 55 miles) per pixel, and south polar coverage from July 2004, at an image scale of 2 kilometers (1.3 miles) per pixel. The images were obtained using a narrow band filter centered at 938 nanometers -- a near-infrared wavelength (invisible to the human eye) at which light can penetrate Titan's atmosphere to reach the surface and return through the atmosphere to be detected by the camera. The images have been processed to enhance surface details. It is currently northern winter on Titan, so the moon's high northern latitudes are not illuminated, resulting in the lack of coverage north of 45 degrees north latitude. Clouds near the south pole (see http://photojournal.jpl.nasa.gov/catalog/PIA06110) have also been removed (south of -75 degrees). At 5,150 kilometers (3,200 miles) across, Titan is one of the solar system's largest moons.

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