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Watch Saturn’s Moons Race Inside the Rings

Saturn's moons Prometheus and Atlas are captured by Cassini in these images from Aug. 23, 2016

Saturn’s moons Prometheus and Atlas are captured by Cassini in these images from Aug. 23, 2016

Round and round they go… the animation above, made from 14 raw images taken by NASA’s Cassini spacecraft on August 23, 2016, shows the moons Prometheus and Atlas orbiting Saturn within the Roche Division gap between its A (top right) and F (center) rings. The gravitational tug of Prometheus (92 miles / 148 km long) is strong enough to pull on the fine, smoke-like icy particles of the F ring, creating streamer and “clump” features that follow it along.

The much smaller Atlas (23 miles / 37 km wide) follows a path around Saturn just past the outer edge of the A ring. It was once thought to be a “shepherd moon” of the A ring, but it’s now known that the pull of the more distant Janus and Epimetheus are responsible for that.

Atlas does have its very own ring, though—a very faint (i.e., not visible above) band of material that runs along its orbit named R/2004 S 1, discovered by the Cassini mission in July 2004.

Image credit: NASA/JPL-Caltech/SSI. Animation by Jason Major.

Bend It Like Saturn

Saturn's atmosphere distorts the line of the rings beyond in this raw image from Cassini (NASA/JPL-Caltech/SSI)

Saturn’s atmosphere distorts the line of the rings beyond in this raw image from Cassini (NASA/JPL-Caltech/SSI)

The lines of Saturn’s rings appear to get sharply bent as their reflected light passes through the upper atmosphere of the planet before being captured by Cassini’s camera in this raw image, acquired on June 9, 2016.

Enormous Saturn of course is, by volume, nearly all atmosphere with a solid core only about the size of Earth. The bands of tans, blues, purples and pale greens we see in Cassini images are just the tops of clouds, and even more transparent layers of atmosphere exist above those, gradually fading out into space. Like what astronauts see from orbit when the Moon passes behind these upper layers, getting squished in the process, Saturn’s rings appear to be distorted by the same refractive process for Cassini. It’s literally an optical illusion, as obviously the rings aren’t changing shape at all!

The image above has been cropped and rotated for artistic effect; see the original raw image here.

Enceladus’ Jets: the Farther They Are, the Harder They Spray

Enceladus surrounds Saturn with its icy spray

Plumes of icy vapor erupt from cracks in Enceladus’ south pole. (NASA/JPL-Caltech/SSI)

A crowning achievement of the Cassini mission to Saturn is the discovery of water vapor jets spraying out from Enceladus‘ southern pole. First witnessed by the spacecraft in 2005, these icy geysers propelled the little 320-mile-wide moon into the scientific spotlight. After 22 flybys of Enceladus during its nearly twelve years in orbit around Saturn, Cassini has gathered enough data to determine that there is a global subsurface ocean of salty liquid water beneath Enceladus’ frozen crust—an ocean that gets literally sprayed into space.  Now, new findings from Cassini and researchers at the Planetary Science Institute—with a little help from a star called Epsilon Orionis—has shown that at least some of the vapor jets get a boost in activity when Enceladus is farther from Saturn.

Read the full story on Universe Today.

Pale Blue Dot: Our Valentine from Voyager 1

If you’re in love with space exploration then you’ll fall for this: a picture of Earth (and five other planets) taken from the Voyager 1 spacecraft after it passed the orbit of Pluto in 1990, 26 years ago today. That image of our planet from almost 4 billion miles away inspired Carl Sagan to write his famous “Pale Blue Dot” passage, and reminds us that we are all just floating on “a mote of dust suspended in a sunbeam.”

This is from a post I originally published in 2010. I’ll keep trotting it out until it’s not cool anymore. (Which I don’t think will ever will NEVER happen.)

Venus, Earth, Jupiter, Saturn, Uranus and Neptune as seen by Voyager 1 in 1990 (Credit: NASA)

On February 14, 1990, after nearly 13 years of traveling the solar system, the Voyager 1 spacecraft passed the orbit of Pluto and turned its camera around to take a series of photos of the planets. The image above shows those photos, isolated from the original series and are left to right, top to bottom: Venus, Earth, Jupiter, Saturn, Uranus, and Neptune.

From that distance, over 4 billion miles from the Sun, the planets each appear as little more than a bright dot against the vastness of interplanetary space.

“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”

– Carl Sagan

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And the Award for Leading Trojan Moon Goes To…

Raw image of Telesto from Cassini's narrow-angle camera on Jan. 14, 2016. (NASA/JPL-Caltech/SSI)

Raw image of Telesto from Cassini’s narrow-angle camera on Jan. 14, 2016. (NASA/JPL-Caltech/SSI)

Drumroll please… the little moon Telesto! (You like it, you really like it!) This image, captured by Cassini on Jan. 14, 2016, shows Saturn’s moon Telesto – a “leading trojan” of the much larger satellite Tethys.

A trojan moon is one that orbits a parent body within the same path as a more massive satellite, positioned at the Lagrangian points L4 and L5… usually at 60º ahead and behind within the orbit relative to the overall center (which, in the case of Tethys, is Saturn.)

The irregularly-shaped, 15-mile (24-km) -wide Telesto rides around Saturn ahead of Tethys, making it the moon’s “leading” trojan. Its slightly larger sister Calypso follows behind Tethys as the trailing trojan. All three orbit the ringed planet at a distance of over 183,000 miles (294,000 km).

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Cassini Has Made Its Last Pass by Enceladus. Here Are the Pictures.

The limb of Enceladus imaged by Cassini from a distance of 15,000 miles (24,000 kilometers) on Dec. 19, 2015. (NASA/JPL/SSI)

The limb of Enceladus imaged by Cassini from a distance of 15,000 miles (24,000 kilometers) on Dec. 19, 2015. (NASA/JPL/SSI)

After nearly eleven and a half years in orbit around Saturn the Cassini spacecraft has made its last-ever targeted flyby of Enceladus, the 320-mile-wide moon of Saturn that has intrigued scientists and the public alike with its active water ice geysers for more than a decade since their discovery. On Saturday Dec. 19, 2015, Cassini performed its E-22 flyby of Enceladus, coming within 3,106 miles (5,000 km) of the moon’s fractured and frozen surface as it sped by at over 21,000 mph. It captured some incredible images along the way, including the one above showing a crescent-lit Enceladus from its night side silhouetted against the hazy upper atmosphere of Saturn, 150,000 miles beyond.

Take a look through some more raw images from the E-22 flyby below.

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