Shadowy Rings

Shadows seem ubiquitous in this Cassini spacecraft view of Saturn's rings captured shortly after the planet's August 2009 equinox.

The moon Pan (28 kilometers, or 17 miles across) casts a long shadow towards the right from where it orbits in the Encke Gap of the A ring in the upper right of the image. A structure in the thin F ring casts a short shadow on that ring in the upper left of the image. Kinky ringlets in the Encke Gap also cast many shadows in the middle and lower portions of the image, but some of those shadows appear faint.

The novel illumination geometry that accompanies equinox lowers the Sun's angle to the ringplane, significantly darkens the rings, and causes out-of-plane structures to look anomalously bright and cast shadows across the rings. These scenes are possible only during the few months before and after Saturn's equinox, which occurs only once in about 15 Earth years. Before and after equinox, Cassini's cameras have spotted not only the predictable shadows of some of Saturn's moons (see PIA11657), but also the shadows of newly revealed vertical structures in the rings themselves (see PIA11665).

Two background stars are visible in this image.

This view looks toward the northern, sunlit side of the rings from about 11 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on August 19, 2009. The view was acquired at a distance of approximately 2.3 million kilometers (1.4 million miles) from Saturn. Image scale is 13 kilometers (8 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

The Shadow of Mimas

The moon Mimas casts a shadow and creates a single blemish on the kingly crescent of Saturn.

Mimas is not shown in this view, but its shadow can be seen on the planet just north of the rings and their shadow. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken with the Cassini spacecraft wide-angle camera on October 25, 2009 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 2.5 million kilometers (1.6 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 116 degrees. Image scale is 144 kilometers (90 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Enceladus

At least four distinct plumes of water ice spew out from the south polar region of Saturn's moon Enceladus in this dramatically illuminated image.

Light reflected off Saturn is illuminating the surface of the moon while the Sun, almost directly behind Enceladus, is backlighting the plumes. See PIA11688 to learn more about Enceladus and its plumes.

This view looks toward the Saturn-facing side of Enceladus (504 kilometers, or 313 miles across). North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on December 25, 2009. The view was obtained at a distance of approximately 617,000 kilometers (383,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 174 degrees. Image scale is 4 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Pandora

The Cassini spacecraft watches Pandora, one of the F ring's two shepherding moons, orbiting beyond the thin ring.

The small moon can be seen on the left of this image. Pandora (81 kilometers, or 50 miles across) is brightly lit on the left by sunlight on the moon's anti-Saturn side and dimly illuminated on the right by light reflected off Saturn on the moon's Saturn-facing side.

See PIA11589 to learn more about how Pandora and another moon, Prometheus, shape the F ring.

This view looks toward the northern, sunlit side of the rings from about 10 degrees above the ringplane. Seven background stars are visible.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 1, 2010. The view was obtained at a distance of approximately 1.4 million kilometers (870,000 miles) from Saturn. Image scale is 8 kilometers (5 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Dione

Like the Voyager spacecraft that came before, the Cassini spacecraft chronicles "wispy" terrain on Saturn's moon Dione.

See PIA10560 to view another image of these bright fractures on the moon's trailing hemisphere. This view looks toward the area between the Saturn-facing side and trailing hemisphere of Dione (1,123 kilometers, or 698 miles across). North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on December 26, 2009. The view was acquired at a distance of approximately 1 million kilometers (621,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 42 degrees. Image scale is 6 kilometers (4 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Saturn, in Infrared

This false-color composite image, constructed from data obtained by NASA's Cassini spacecraft, shows Saturn's rings and southern hemisphere. The composite image was made from 65 individual observations by Cassini's visual and infrared mapping spectrometer in the near-infrared portion of the light spectrum on November 1, 2008. The observations were each six minutes long.

In this image constructed from data collected in the near-infrared wavelengths of light, scientists designated blue to indicate sunlight reflected at a wavelength of 2 microns, green to indicate sunlight reflected at 3 microns and red to indicate thermal emission at 5 microns. Saturn's rings reflect sunlight at 2 microns, but not at 3 and 5 microns, so they appear deep blue. Saturn's high altitude haze reflects sunlight at both 2 and 3 microns, but not at 5 microns, and so it appears green to blue-green. The heat emission from the interior of Saturn is only seen at 5 microns wavelength in the spectrometer data, and thus appears red. The dark spots and banded features in the image are clouds and small storms that outline the deeper weather systems and circulation patterns of the planet. They are illuminated from underneath by Saturn's thermal emission, and thus appear in silhouette.

Photo credit: NASA/JPL/University of Arizona/University of Leicester

Note: For similar images and a movie that highlight Saturn's Auroras Australis, see PIA13402: Glowing Southern Lights,
PIA13403: Four Aurora Snapshots and PIA13404: Dancing Southern Lights of Saturn. A small Quicktime movie of the auroras can be watched here.

Conjoined Moons

Looking like half of a figure eight, two of Saturn's moons appear conjoined in this Cassini spacecraft image.

The moon Dione, at the top in the image, is actually closer to the spacecraft here. However, because of the similar albedo, or reflectivity, of the two moons and because of the location of a particularly large crater near the south polar region of Dione, the moon appears to blend seamlessly with Rhea. The large, faint crater Evander is centered at about 57 degrees south latitude, 145 degrees west longitude and can also be seen in the Dione south polar map (see PIA12579).

Lit terrain seen here is on the anti-Saturn side of Dione (1,123 kilometers, or 698 miles across) and on the area between the anti-Saturn and leading hemisphere on Rhea (1,528 kilometers, or 949 miles across).

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 27, 2010. The view was acquired at a distance of approximately 1.1 million kilometers (684,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 78 degrees. The view was acquired at a distance of approximately 1.6 million kilometers (994,000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 78 degrees. Image scale is 7 kilometers (4 miles) per pixel on Dione and 10 kilometers (6 miles) on Rhea.

Photo credit: NASA/JPL/Space Science Institute

Ten New Lacus Named on Titan

From the USGS Astrogeology Science Center:

Ten names with the descriptor term lacus have been approved for use on Titan. For more information, see the list of Titan feature names and the map of the north polar region of Titan in the Gazetteer of Planetary Nomenclature.

Notes: The ten newly named lakes are (in alphabetical order): Albano Lacus, Atitlán Lacus, Cayuga Lacus, Junín Lacus, Lanao Lacus, Logtak Lacus, Ohrid Lacus, Sevan Lacus, Uvs Lacus, and Vänern Lacus. All names were approved on September 16, 2010. There are now a total of 24 named lakes on Titan.

A Brief Discontinuity in the Space-Time Continuum

This is a quick note to say that my home is going through some renovation work through early next week. Blogging is more or less halted until then, although, if I can find some time to do some posts, I'll try to put up some new material. In the meantime, please feel free to visit the archives of Areology, Ministry of Space Exploration, and Saturnology.

Atlas and F-Ring Shadows

Delicate shadows are cast outward from Saturn's thin F ring in the lower left of this image taken as the planet approached its August 2009 equinox.

The moon Atlas (30 kilometers, or 19 miles across) is seen just above the center of the image between the A ring and thin F ring. Several background stars are also visible.

The novel illumination geometry created around the time of Saturn's August 2009 equinox allows out-of-plane structures and moons orbiting in or near the plane of Saturn's equatorial rings to cast shadows onto the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. To learn more about this special time and to see movies of moons' shadows moving across the rings, see PIA11651 and PIA11660.

This view looks toward the northern, unilluminated side of the rings from about 8 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 11, 2009. The view was obtained at a distance of approximately 1.098 million kilometers (682,000 miles) from Atlas. Image scale is 7 kilometers (4 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute