Starship Asterisk*

PIA12661: Cutting Off Rhea (Credit: NASA/JPL/SSI)

---

Saturn's rings and small moon Prometheus obscure the Cassini spacecraft's view of the planet's second largest moon, Rhea.

Prometheus, which orbits in the Roche Division between the main rings and the thin F ring, can be seen just below the center of the image, in front of Rhea. Lit terrain seen here is on the anti-Saturn side of Prometheus (86 kilometers, or 53 miles across) and mostly on the leading hemisphere of Rhea (1,528 kilometers, or 949 miles across).

This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible red light with the Cassini spacecraft narrow-angle camera on April 9, 2010. The view was acquired at a distance of approximately 1 million kilometers (621,000 miles) from Prometheus and 1.6 million kilometers (994,000 miles) from Rhea. Image scale is 6 kilometers (4 miles) per pixel on Prometheus and 10 kilometers (6 miles) per pixel on Rhea.

PIA12663: Flying Over Dione (Credit: NASA/JPL/SSI)

---

The Cassini spacecraft swooped in for a close-up of the cratered, fractured surface of Saturn's moon Dione in this image taken during the spacecraft's Jan. 27, 2010, non-targeted flyby.

Cassini came within about 45,000 kilometers (28,000 miles) of the moon during this flyby, and this image was acquired at a distance of approximately 46,000 kilometers (29,000 miles). See Wispy Marble for an older, closer view of Dione.

This view looks toward the leading hemisphere of Dione (1,123 kilometers, or 698 miles across). North on Dione is up. The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was acquired at a Sun-Dione-spacecraft, or phase, angle of 108 degrees. Image scale is 270 meters (886 feet) per pixel.

Click to view full size image

PIA12666: Tethys_and_Darker_Dione

Saturn's moon Dione, in the foreground of this Cassini image, appears darker than the moon Tethys.

Tethys appears brighter because it has a higher albedo than Dione, meaning Tethys reflects more sunlight. This higher albedo is due to Tethys being closer to the moon Enceladus and the E ring which coats these moons in fresh, bright debris spewing from Enceladus.

Because of the particular viewing geometry here, lit terrain seen here is on the anti-Saturn side of Dione (1123 kilometers, 698 miles across) while lit terrain on Tethys (1062 kilometers, 660 miles across) is on the leading hemisphere of that moon.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on March 23, 2010. The view was obtained at a distance of approximately 1.2 million kilometers (745,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 88 degrees. The view was obtained at a distance of approximately 1.8 million kilometers (1.1 million miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 88 degrees. Image scale is 7 kilometers (4 miles) per pixel on Dione and 11 kilometers (7 miles) per pixel on Tethys.

Credit: NASA/JPL/SSI

Click to view full size image

Herschel Crater features prominently on the moon Mimas in this Cassini spacecraft image, which gives the impression of an eye staring out into space.

Herschel Crater is about 130 kilometers, or 81 miles, wide and covers a significant part of the moon. This view looks toward the leading hemisphere of Mimas (396 kilometers, or 246 miles across). North on Mimas is up and rotated 1 degree to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 3, 2010. The view was acquired at a distance of approximately 476,000 kilometers (296,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 56 degrees. Image scale is 3 kilometers (2 miles) per pixel.

PIA12669: Staring Into Space
Image Credit: NASA/JPL/SSI

Click to view full size image

Taken in 1989 by Voyager 2 during its flyby of the Neptune system, this is a global color mosaic of Triton. The color was synthesized by combining high-resolution images taken through orange, violet and ultraviolet filters; these images were displayed as red, green, and blue images and combined to create this color version.

With a radius about 22 percent smaller than Earth's moon, Triton is the largest satellite of Neptune and is one of the few bodies in the solar system known to have a nitrogen-dominated atmosphere. The others are Earth and Saturn's giant moon, Titan.

Triton is so cold that most of its nitrogen is condensed as frost, making it the only satellite in the solar system known to have a surface made mainly of nitrogen ice. The pinkish deposits constitute a vast south polar cap believed to contain methane ice, which would have reacted under sunlight to form pink or red compounds. The dark streaks overlying these pink ices are believed to be an icy and perhaps carbonaceous dust deposited from huge geyser-like plumes, some of which were found to be active during the Voyager 2 flyby.

The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas includes what is called the cantaloupe terrain, whose origin is unknown, and a set of "cryovolcanic" landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton's interior.

Image Credit: NASA/JPL/USGS

Click to view full size image

PIA12676: Melanthius on Tethys

The Cassini spacecraft looks toward an area between the trailing hemisphere and anti-Saturn side of Tethys and spies the large crater Melanthius near the moon's south pole.

Melanthius, at the bottom of this image, is about 250 kilometers (155 miles) wide on Tethys. See PIA10412: On the South Side for another view. North on Tethys (1,062 kilometers, or 660 miles across) is up and rotated 19 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 29, 2010. The view was acquired at a distance of approximately 670,000 kilometers (416,000 miles) from Tethys and at a sun-Tethys-spacecraft, or phase, angle of 41 degrees. Image scale is 4 kilometers (2 miles) per pixel.

Credit: NASA/JPL/SSI

owlice wrote:

A previously-speculated but little-known NASA mission has been successfully completed. Two probes were sent to the moon to do further experiments on the lunar surface, some of which necessitated lighting up the fields of experimentation. Miniature rovers were released from the probes to gather information; tracking was done both through radio signals and visually, requiring that the fields be lit. Alert amateur and professional astronomers were stunned to see and capture this and similar images of the moon during the 20-minute period that portions of the moon were flooded with artificial light. Though initially the experiments were to run while the moon was new, the launching of the probes was delayed due to bad weather and the experiments were performed instead during the crescent phase.