Astronomy Picture of the Day

February 1, 2005

Saturn's Iapetus: Moon with a Strange Surface
What has happened to Saturn's moon Iapetus? A strange ridge crosses the moon near the equator, visible near the bottom of the above image, making Iapetus appear similar to the pit of a peach. Half of Iapetus is so dark that it can nearly disappear when viewed from Earth. Recent observations show that the degree of darkness of the terrain is strangely uniform, like a dark coating was somehow recently applied to an ancient and highly cratered surface. The other half of Iapetus is relatively bright but oddly covered with long and thin streaks of dark. A 400-kilometer wide impact basin is visible near the image center, delineated by deep scarps that drop sharply to the crater floor. The above image was taken by the Saturn-orbiting Cassini spacecraft during a flyby of Iapetus at the end of last year.

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February 2, 2005

Going with the Flow
Lanes of cold gas in Saturn's mostly hydrogen atmosphere brush past each other, often creating spectacular patterns like those seen here. The whirling shapes near the bottom of this view suggest turbulent interactions between latitudinal regions of different densities moving at different speeds, while the long, linear shapes in the lanes above suggest more stable conditions in the flow there. The image of Saturn's southern hemisphere was taken with the Cassini spacecraft narrow angle camera on Dec. 5, 2004, at a distance of approximately 3.4 million kilometers (2.1 million miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 727 nanometers. The image scale is 40 kilometers (25 miles) per pixel. Contrast was enhanced to aid visibility of features in the atmosphere.

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Titan: A World of Its Own

Story from

[url=http://setiweb.ssl.berkeley.edu/forum_thread.php?id=3067]S@h Berkeley's Staff Friends Club m7 ©

update, because the Story is over 60 Minutes, so ne edit

S@h Berkeley's Staff Friends Club m7 ©

February 3, 2005

January's Moon
The month of January is named for the mythical Roman god Janus, who guarded the gate of heaven. Cassini spied the heavily cratered, irregularly shaped moon of Saturn as it glided along in its orbit, about 11,000 kilometers (6,800 miles) beyond the bright core of the narrow F ring. Only vague hints of the moon's surface morphology are visible from this distance. Janus is 181 kilometers (113 miles) across. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 22, 2005, at a distance of approximately 2.5 million kilometers (1.6 million miles) from Saturn. The image scale is 15 kilometers (9 miles) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility.

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February 03, 2005

Saturn's Bull's-Eye Marks its Hot Spot - (PIC1) - (PIC2)
NASA astronomers using the Keck I telescope in Hawaii are learning much more about a strange, thermal "hot spot" on the tip of Saturn's south pole. In the most precise reading of Saturn's temperatures ever taken from Earth, a new set of infrared images suggests a warm "polar vortex" at Saturn's south pole - the first warm polar cap ever to be discovered in the solar system. The vortex is punctuated by a compact spot that is the warmest place on the planet. The researchers report their findings in the Feb. 4 issue of the journal Science...

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February 4, 2005

Rhea in Natural Color
The trailing hemisphere of Saturn's moon Rhea seen here in natural color, displays bright, wispy terrain that is similar in appearance to that of Dione, another one of Saturn's moon. At this distance however, the exact nature of these wispy features remains tantalizingly out of the reach of Cassini's cameras. At this resolution, the wispy terrain on Rhea looks like a thin coating painted onto the moon's surface. Cassini images from December 2004 (see http://photojournal.jpl.nasa.gov/jpeg/PIA06163.jpg) revealed that, when seen at moderate resolution, Dione's wispy terrain is comprised of many long, narrow and braided fractures. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired with the Cassini spacecraft narrow angle camera on Jan. 16, 2005, at a distance of approximately 496,500 kilometers (308,600 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 35 degrees. Resolution in the original image was about 3 kilometers (2 miles) per pixel. The image has been rotated so that north on Rhea is up. Contrast was enhanced and the image was magnified by a factor of two to aid visibility.

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February 7, 2005

Bright Moon in Darkness
In the dim light of the outer solar system, Cassini gazed back at Saturn's brightest gem -- the moon Enceladus. The icy little world presents only a slim crescent in this natural color view. Cassini has now matched the best spatial resolution on Enceladus achieved by NASA's Voyager spacecraft, and will soon have excellent coverage of the moon (at more than 10 times the resolution in this image), following a flyby planned for February 17. When seen from its day side, Enceladus (499 kilometers, or 310 miles across) has one of the brightest and whitest surfaces in the solar system. Since it reflects most of the sunlight that strikes it, the temperature there remains at a chilly -200 degrees Celsius (-330 degrees Fahrenheit). In this view, Cassini was pointed at the leading hemisphere of Enceladus, which was in darkness at the time. The image has been rotated so that north on Enceladus is up. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired with the Cassini spacecraft narrow angle camera on Jan. 16, 2005, at a distance of approximately 209,300 kilometers (130,100 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 148 degrees. Resolution in the original image was about 1 kilometer (0.6 miles) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility.

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February 8, 2005

Titan - 3 Mission Description
The third targeted flyby of Titan occurs on Tuesday, February 15, 2005 at 6:58 SCET (Ground: 8:06 UTC -- 12:06 AM Pacific time). Cassini's closest approach to Saturn's largest satellite is at an altitude of 1577 km (980 miles) above the surface at a speed of 6.1 kilometers per second (14,000 mph). Titan has a diameter of 5150 km (3200 miles), so the spacecraft passes within 1.6 Titan radii.

Cassini Science Presentations - AUTO UPDATES!

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February 8, 2005

Mixing Saturn
Intricate undulations and swirls within the banded atmosphere of Saturn give scientists clues to the processes occurring there. The lower part of the image shows the characteristic billows that form at the turbulent boundary between two air masses of different densities moving at different speeds. This can be contrasted with the dark band just to the north that shows linear features moving in an apparently stable region with no obvious turbulent mixing from north to south. The bright band farther north appears to have the same morphology. At the top of the image, a dark oval-shaped storm resides in a band where a chevron pattern dominates. The chevron pattern is suggestive of a place where momentum is being redistributed in Saturn's atmosphere. The image of Saturn's southern hemisphere was taken with the Cassini spacecraft narrow angle camera on Dec. 6, 2004, at a distance of approximately 3.4 million kilometers (2.1 million miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 727 nanometers. The image scale is 40 kilometers (25 miles) per pixel. Contrast was enhanced to aid visibility of features in the atmosphere.

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February 8, 2004

Mimas Blues
Mimas drifts along in its orbit against the azure backdrop of Saturn's northern latitudes in this true color view. The long, dark lines on the atmosphere are shadows cast by the planet's rings. Saturn's northern hemisphere is presently relatively cloud-free, and rays of sunlight take a long path through the atmosphere. This results in sunlight being scattered at shorter (bluer) wavelengths, thus giving the northernmost latitudes their bluish appearance at visible wavelengths. At the bottom, craters on icy Mimas (398 kilometers, or 247 miles across) give the moon a dimpled appearance. Images taken using infrared (930 nanometers), green (568 nanometers) and ultraviolet (338 nanometers) spectral filters were combined. The colors have been adjusted to match closely what the scene would look like in natural color. See http://photojournal.jpl.nasa.gov/catalog/PIA06142 for a similar view in natural color. The images were obtained using the Cassini spacecraft narrow angle camera on Jan. 18, 2005, at a distance of approximately 1.4 million kilometers (870,000 miles) from Saturn. Resolution in the image is 8.5 kilometers (5.3 miles) per pixel on Saturn and 7.5 kilometers (4.7 miles) per pixel on Mimas. The image has been contrast-enhanced to aid visibility.

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February 8, 2005

Saturn's Blue Cranium
Saturn's northern hemisphere is presently a serene blue, more befitting of Uranus or Neptune, as seen in this natural color image from Cassini. Light rays here travel a much longer path through the relatively cloud-free upper atmosphere. Along this path, shorter wavelength blue light rays are scattered effectively by gases in the atmosphere, and it is this scattered light that gives the region its blue appearance. Why the upper atmosphere in the northern hemisphere is so cloud-free is not known, but may be related to colder temperatures brought on by the ring shadows cast there. Shadows cast by the rings surround the pole, looking almost like dark atmospheric bands. The ring shadows at higher latitudes correspond to locations on the ringplane that are farther from the planet -- in other words, the northernmost ring shadow in this view is made by the outer edge of the A ring. Spots of bright clouds also are visible throughout the region. This view is similar to an infrared image obtained by Cassini at nearly the same time; see http://photojournal.jpl.nasa.gov/catalog/PIA06567 The infrared view shows a great deal more detail in the planet's atmosphere, however. Images obtained using red, green and blue spectral filters were combined to create this color view. The images were taken with the Cassini spacecraft wide angle camera on Dec. 14, 2004, at a distance of 719,200 kilometers (446,900 miles) from Saturn. The image scale is about 39 kilometers (24 miles) per pixel.

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February 9, 2005

Wrinkles of Youth?
This Cassini image of Saturn's moon Enceladus shows a region containing bizarre, wrinkled terrain. Enceladus is covered with bright water ice. The part of its surface visible here appears to be largely free of craters -- indicating that it is geologically young. The first close imaging of this moon will be done by Cassini in February 2005 and should reveal many surprises. Enceladus has a diameter of 499 kilometers (310 miles). This view shows primarily the leading hemisphere of Enceladus. The image has been rotated so that north on Enceladus is up. The image was acquired with the Cassini spacecraft narrow angle camera on Jan. 15, 2005, at a distance of approximately 367,000 kilometers (228,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 74 degrees. A combination of spectral filters sensitive to infrared and polarized light was used to obtain this view. Resolution in the original image was about 2 kilometers (1.2 miles) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility.

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February 9, 2005

NASA Observations Help Determine Titan Wind Speeds
Strong westerly winds of up to about 400 kilometers per hour (250 miles per hour) buffeted the Huygens probe as it descended through Titan's upper atmosphere last month, according to NASA-led observations of the probe transmissions with Earth-based radio telescopes. The winds eased to a mild breeze near the surface of Titan, Saturn's largest moon...

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February 10, 2005

Hershel Dead-On
Saturn's moon Mimas has many large craters, but its Herschel crater dwarfs all the rest. This large crater 130 kilometers wide (80 miles) has a prominent central peak, seen here almost exactly on the terminator. This crater is the moon's most prominent feature, and the impact that formed it probably nearly destroyed Mimas. Mimas is 398 kilometers (247 miles) across. This view is predominantly of the leading hemisphere of Mimas. The image has been rotated so that north on Mimas is up. This image was taken with the Cassini spacecraft narrow angle camera on Jan. 16, 2005, at a distance of approximately 213,000 kilometers (132,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 84 degrees. Resolution in the original image was about 1.3 kilometers (0.8 miles) per pixel. A combination of spectral filters sensitive to ultraviolet and polarized light was used to obtain this view. Contrast was enhanced and the image was magnified by a factor of two to aid visibility.

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Cassini's Fourth Flyby of Titan Will Include
First-Ever Overlapping RADAR and Imaging;
First Close Pass By Enceladus to Follow
by Emily Lakdawalla

February 10, 2005

Cassini is swooping in towards Saturn, aiming for, the mission's fourth close flyby and gravity assist from the giant moon Titan. The closest approach will take place on February 15 at 06:58 UTC (February 14 at 10:58 p.m. Pacific time), passing within 1577 kilometers (980 miles) of the moon's surface. The flyby is known as "Titan-3" or "T3" to mission planners, even though it's the fourth flyby. During the third flyby, called "Titan-C," Cassini obtained no data because it was focused on Huygens as the little probe descended. Titan-3 will be Cassini's first encounter with Titan in which it is unencumbered by Huygens. However, it will cover largely the same region of Titan's globe that was visible during the Titan-B flyby on December 13.
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Full Story at The Planetary Society

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

February 11, 2005

The Great Rift
Ithaca Chasma is one of the two most prominent features on Saturn's moon Tethys; the other is the gigantic crater Odysseus. Ithaca Chasma is visible near the moon's lower right limb in this image, which does not reveal the branching canyon's full extent. Tethys is 1,060 kilometers (659 miles) across. Discovered in NASA Voyager images, the chasm is 100 kilometers (60 miles) across on average, and is 4 kilometers (2 miles) deep in places. It stretches more than 1,000 kilometers (620 miles) over Tethys' surface, from north to south. This view is roughly centered on the leading hemisphere of Tethys. The image has been rotated so that north on Tethys is up. This view was obtained with the Cassini spacecraft narrow angle camera on Jan. 17, 2005, at a distance of approximately 1 million kilometers (621,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 110 degrees. A spectral filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers was used to capture the image. Resolution in the original image was about 6 kilometers (3.7 miles) per pixel. Contrast was enhanced and the image was magnified by a factor of two to aid visibility.

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February 11, 2005

Panoramic Rings - (PIC) - (VIDEO)
Saturn's most prominent feature, its dazzling ring system, takes center stage in this stunning natural color mosaic which reveals the color and diversity present in this wonder of the solar system. Gaps, gravitational resonances and wave patterns are all present, and the delicate color variations across the system are clearly visible. Click VIDEO above to view a QuickTime video (5.5 MB) closeup. This mosaic of six images covers a distance of approximately 62,000 kilometers along the ring plane, from a radius of 74,565 kilometers to 136,780 kilometers (46,333 to 84,991 miles) from the planet's center. This view is from Cassini's vantage point beneath the ring plane. The rings are tilted away from Cassini at an angle of about 4 degrees. Images taken using red, green and blue spectral filters were used to create this natural color mosaic. The images were acquired using the Cassini spacecraft narrow angle camera on Dec. 12, 2004, at a distance of approximately 1.8 million kilometers (1.1 million miles). The image scale is 10.5 kilometers (6.5 miles) per pixel.

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First measurement of Titan’s winds from Huygens

February 09, 2005

Using a global network of radio telescopes, scientists have measured the speed of the winds faced by Huygens during its descent through the atmosphere of Titan.

February 14, 2005

Vortex Flow
The study of a planetary atmosphere like Saturn's is quite different from studying solid surfaces, since atmospheres are dynamic and ever-changing. In this Cassini image, the large-scale curvilinear pattern suggests flow around the vortices in the center of the image. However, the fine-scale linear striations are themselves notable for their indication of the stability of the flow in this region. Cassini imaging scientists make repeated observations -- including making movies -- of Saturn's atmosphere in order to track storms and other features and watch how the planet's dynamic atmosphere changes over time. This image was taken with the Cassini spacecraft narrow angle camera on Dec. 6, 2004, at a distance of about 3.3 million kilometers (2 million miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 727 nanometers. The image scale is 39 kilometers (24 miles) per pixel.

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