Hello! You’ll noticed that I skipped Astronomy Pictures of the Week on Wednesday. That… was on purpose.
Today was Cassini’s last day alive. This morning, Cassini plunged into Saturn, sending back some amazing data, but, in the process, ending its life.
Cassini was launched on October 15th, 1997. For two decades, Cassini revealed the wonders of the greatest planet and planetary system in our solar system to us. We learned so much.
But, now, it’s over…
Cassini gazes across the icy rings of Saturn toward the icy moon Tethys, whose night side is illuminated by Saturnshine, or sunlight reflected by the planet.
Tethys was on the far side of Saturn with respect to Cassini here; an observer looking upward from the moon’s surface toward Cassini would see Saturn’s illuminated disk filling the sky.
Tethys was brightened by a factor of two in this image to increase its visibility. A sliver of the moon’s sunlit northern hemisphere is seen at top. A bright wedge of Saturn’s sunlit side is seen at lower left.
Back to Cassini’s Grand Finale… today we’re highlighting Titan…
NASA’s Cassini spacecraft looks toward the night side of Saturn’s moon Titan in a view that highlights the extended, hazy nature of the moon’s atmosphere. During its long mission at Saturn, Cassini has frequently observed Titan at viewing angles like this, where the atmosphere is backlit by the Sun, in order to make visible the structure of the hazes.
Titan’s high-altitude haze layer appears blue here, whereas the main atmospheric haze is orange. The difference in color could be due to particle sizes in the haze. The blue haze likely consists of smaller particles than the orange haze.
Cassini’s Grand Finale…
The thin sliver of Saturn’s moon Prometheus lurks near ghostly structures in Saturn’s narrow F ring in this view from NASA’s Cassini spacecraft. Many of the narrow ring’s faint and wispy features result from its gravitational interactions with Prometheus (86 kilometers, or 53 miles across).
Most of the small moon’s surface is in darkness due to the viewing geometry here. Cassini was positioned behind Saturn and Prometheus with respect to the sun, looking toward the moon’s dark side and just a bit of the moon’s sunlit northern hemisphere.
Also visible here is a distinct difference in brightness between the outermost section of Saturn’s A ring (left of center) and rest of the ring, interior to the Keeler Gap (lower left).
This view looks toward the sunlit side of the rings from about 13 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 13, 2017.
The view was acquired at a distance of approximately 680,000 miles (1.1 million kilometers) from Saturn. Image scale is 4 miles (6 kilometers) per pixel.
Click the image for the tif file…
Late on this one… by a week… I know why I’m missing these, too… real life has me extra stressed… 🙁
Anyways… here’s more from Cassini’s Grand Finale…
This false-color view from NASA’s Cassini spacecraft gazes toward the rings beyond Saturn’s sunlit horizon. Along the limb (the planet’s edge) at left can be seen a thin, detached haze. This haze vanishes toward the left side of the scene.
As usual… click on the image for the tif download…
I also realize I missed last week’s APotW. Apologies…
Continuing on with the Grand Finale…
This image was taken on May 29, 2017, with the Cassini spacecraft narrow-angle camera. The image was acquired on the sunlit side of the rings from a distance of about 39,800 miles (64,100 kilometers) away from the area pictured. The image scale is 1,460 feet (445 meters) per pixel. The phase angle, or sun-ring-spacecraft angle, is 137 degrees.
(See the bottom of the post for the links to download the associated .tif images…)
As usual until September, this is from Cassini’s Grand Finale…
The light of a new day on Saturn illuminates the planet’s wavy cloud patterns and the smooth arcs of the vast rings.
The light has traveled around 80 minutes since it left the sun’s surface by the time it reaches Saturn. The illumination it provides is feeble; Earth gets 100 times the intensity since it’s roughly ten times closer to the sun. Yet compared to the deep blackness of space, everything at Saturn still shines bright in the sunlight, be it direct or reflected.
This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Feb. 25, 2017 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 939 nanometers.
The view was obtained at a distance of approximately 762,000 miles (1.23 million kilometers) from Saturn. Image scale is 45 miles (73 kilometers) per pixel.
Another one from Cassini’s Grand Finale. And yeah, I’m a day late.
NASA’s Cassini spacecraft sees bright methane clouds drifting in the summer skies of Saturn’s moon Titan, along with dark hydrocarbon lakes and seas clustered around the north pole.
Compared to earlier in Cassini’s mission, most of the surface in the moon’s northern high latitudes is now illuminated by the sun. (See here for a view of the northern hemisphere from 2007.) Summer solstice in the Saturn system occurred on May 24, 2017.
The image was taken with the Cassini spacecraft narrow-angle camera on June 9, 2017, using a spectral filter that preferentially admits wavelengths of near-infrared light centered at 938 nanometers. Cassini obtained the view at a distance of about 315,000 miles (507,000 kilometers) from Titan.
As usual, click on the image for the .tif download…
We continue with images from Cassini’s Grand Finale. This time, it’s an image from over Saturn’s north pole, with a teeny tiny dot, Mimas, in the upper right…
From high above Saturn’s northern hemisphere, NASA’s Cassini spacecraft gazes over the planet’s north pole, with its intriguing hexagon and bullseye-like central vortex.
Saturn’s moon Mimas is visible as a mere speck near upper right. At 246 miles (396 kilometers across) across, Mimas is considered a medium-sized moon. It is large enough for its own gravity to have made it round, but isn’t one of the really large moons in our solar system, like Titan. Even enormous Titan is tiny beside the mighty gas giant Saturn.
This view looks toward Saturn from the sunlit side of the rings, from about 27 degrees above the ring plane. The image was taken in green light with the Cassini spacecraft wide-angle camera on March 27, 2017.
The view was acquired at a distance of approximately 617,000 miles (993,000 kilometers) from Saturn. Image scale is 37 miles (59 kilometers) per pixel. Mimas’ brightness has been enhanced by a factor of 3 in this image to make it easier to see.
Another one from Cassini’s Grand Finale mission…
Here’s the text from the photo page; the image is below the fold (and, as usual, you can click on it for the tiff download)…
Before Cassini entered its Grand Finale orbits, it acquired unprecedented views of the outer edges of the main ring system. For example, this close-up view of the Keeler Gap, which is near the outer edge of Saturn’s main rings, shows in great detail just how much the moon Daphnis affects the edges of the gap.
This image was part of a mosaic that included Daphnis (The Realm of Daphnis).
Daphnis creates waves in the edges of the gap through its gravitational influence. Some clumping of ring particles can be seen in the perturbed edge, similar to what was seen on the edges of the Encke Gap back when Cassini arrived at Saturn in 2004.
This view looks toward the sunlit side of the rings from about 3 degrees above the ring plane. The view was acquired at a distance of approximately 18,000 miles (30,000 kilometers) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 69 degrees. Image scale is 581 feet (177 meters) per pixel. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 16, 2017.