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Dear Jupiter: Use More Sunscreen

Image of Jupiter's Great Red Spot from Voyager 1, 1979 data. Edited by Björn Jónsson.

Image of Jupiter’s Great Red Spot from Voyager 1, 1979 data. Edited by Björn Jónsson.

It’s the signature accessory of the largest planet in our solar system: Jupiter’s Great Red Spot, an enormous anticyclone over twice the width of our entire planet. Visible in even modest backyard telescopes, the GRS has been churning away for at least several hundred years. But, based on recent analysis of data gathered by the Cassini spacecraft during its pass by Jupiter in December 2000, the Great Red Spot’s rusty coloration may actually only be skin-deep – a “sunburn” created by interaction between Jupiter’s upper atmosphere and solar radiation.

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Saturn and Titan Show Off Their Crescents

Cassini image of Saturn and Titan from Aug. 11, 2013 (NASA/JPL-Caltech/SSI)

Cassini image of Saturn and Titan from Aug. 11, 2013 (NASA/JPL-Caltech/SSI)

It may not be in color but that doesn’t make it any less beautiful: this stunning image from Cassini shows Saturn and its largest moon Titan – the second-largest moon in our solar system, after Jupiter’s Ganymede – from their night sides, both showing their crescents against the blackness of space.

Titan’s crescent nearly wraps all the way around its globe, because of the way its thick atmosphere scatters sunlight.

The view was obtained at a distance of approximately 1.1 million miles (1.7 million kilometers) from about 3 degrees above the ringplane. The image was taken in violet wavelengths with Cassini’s wide-angle camera (WAC) on Aug. 11, 2013.

Source: NASA/JPL

Cassini Spots the Sun Shining on Titan’s Sea

Infrared mosaic image showing sunglint off Titan's Kraken Mare. (NASA/JPL-Caltech/University of Arizona/University of Idaho)

Infrared mosaic image showing sunglint off Titan’s Kraken Mare. (NASA/JPL-Caltech/University of Arizona/University of Idaho)

There’s nothing like the beautiful reflection of sunlight off the mirrored surface of a lovely lake… regardless if you’re on Earth or Saturn’s moon Titan! This picture, a mosaic of images acquired by Cassini’s Visual Infrared and Mapping Spectrometer (VIMS) instrument during a flyby on August 21, 2014, shows exactly that: sunglint reflecting off the super-smooth surface of the moon’s largest polar lakes.

(Except unlike on Earth this lake isn’t filled with liquid water but rather liquid methane and ethane!)

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Cassini Watches Clouds Form Over Titan’s Methane Sea

Animation of clouds forming over Ligeia Mare, one of Titan's many large methane lakes (NASA/JPL-Caltech/SSI)

Animation of clouds forming over Ligeia Mare, one of Titan’s many large methane lakes (NASA/JPL-Caltech/SSI)

What’s the weather forecast on Titan? Well if you’re planning a vacation down by the shores of Ligeia Mare you may get some cloudy skies, if what happened at the end of July repeats itself!

The animation above was made from images acquired by Cassini during a flyby of Titan in July 2014, showing the formation and dissipation of bright methane clouds over one of the moon’s polar lakes. Spanning a period of two days, the images reveal what may be the start of summer weather in Titan’s northern hemisphere… or just a bit of isolated “lake effect” cloudiness.

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Cassini Marks Ten Discovery-Filled Years at Saturn

Cassini by the Numbers: an infographic of the spacecraft's achievements over the past decade (NASA/JPL-Caltech)

Cassini by the Numbers: an infographic of the spacecraft’s achievements over the past decade (NASA/JPL-Caltech)

Just a week after Curiosity celebrated its first Martian year in Gale Crater and we have yet another milestone anniversary in Solar System exploration: as of 10:48 p.m. EDT tonight Cassini will have been in orbit around Saturn for a full decade!

“There are times when human language is inadequate, when emotions choke the mind, when the magnitude of events cannot properly be conveyed by the same syllables we use to navigate everyday life. The evening of June 30, 2004 was such a time.” 

– Carolyn Porco, Cassini Imaging Team Leader, CICLOPS “Captain’s Log” on June 30, 2014

That’s ten years and over 2 billion miles of discoveries and explorations of our Solar System’s most majestic planet and its incredibly varied family of moons. Over the course of its primary mission and three extended missions, we have been able to get a close-up look at Saturn and its moons like never before, witnessing first-hand the changes that occur as their seasons change. What’s been discovered by the Cassini mission about Saturn has offered invaluable insight into the evolution of our entire Solar System, as well as planets that could be found elsewhere in our galaxy.

“Having a healthy, long-lived spacecraft at Saturn has afforded us a precious opportunity,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “By having a decade there with Cassini, we have been privileged to witness never-before-seen events that are changing our understanding of how planetary systems form and what conditions might lead to habitats for life.”

Launched on October 15, 1997, the Cassini-Huygens spacecraft established orbit around Saturn on June 30, 2004 (July 1, UTC).

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What’s Ahead for Cassini?


If you’ve been a faithful reader of Lights in the Dark over the past five years you know that I just love Cassini (and you probably do too!) In orbit around Saturn since 2004, Cassini has taken us on an intimate tour of the Saturnian system for a decade now, revealing the incredible beauty of the ringed planet and its family of moons like no spacecraft ever has before. Thanks to Cassini and the Huygens probe, we have seen the surface of Titan for the first time, witnessed the jets of Enceladus, discovered many previously-unknown moons (and moonlets) and basically learned more about Saturn over the past ten years than since Galileo first pointed his telescope at it.

Cassini's final maneuver will be to dive through a gap in Saturn's rings in 2017 (NASA/JPL-Caltech)

Cassini’s will dive through a gap in Saturn’s rings in 2017 and sample the planet’s upper atmosphere (NASA/JPL-Caltech)

Although nearing the end of its life span, Cassini still has a few good years left and scientists are taking full advantage of its remaining time around Saturn to learn as much as they can before the spacecraft makes its final dive into the planet’s atmosphere in 2017.* The video above shows what awaits Cassini in the years ahead — some of its best discoveries may be yet to come. Check it out!

Learn more about the Cassini mission and read about its latest discoveries here and here.

*The exact plan for the end of Cassini’s mission has not yet been finalized.

This is How Saturn’s Rings Would Look to a Butterfly

Ultraviolet image of Saturn's rings acquired by Cassini in 2004 (NASA/JPL-Caltech/University of Boulder)

Ultraviolet image of Saturn’s rings acquired by Cassini in 2004 (NASA/JPL-Caltech/University of Boulder)

You don’t typically see Saturn’s rings looking like this, but then you can’t see in ultraviolet like Cassini (or many insects) can! The image above was acquired by the UVIS (UltraViolet Imaging Spectrograph) instrument aboard the Cassini-Huygens spacecraft on June 30, 2004, just as it was entering orbit around Saturn.

The area shown here is about 10,000 km (6,200 miles) across. It’s a small section of ring segments… just a portion of Saturn’s magnificent expanse of rings. Part of the C ring, toward Saturn, is along the left, and the inner edge of the B ring begins just right of the center. The colors are related to the composition of the ring particles; blue and green colors are from bright water ice, reds are rings with darker, “dirtier” particles.

While the colors aren’t “real” per se — our eyes simply can’t see UV light — the association of colors we can see to specific UV wavelengths allows scientists to accurately observe relative differences in the ring segments.

“It is cool that we can pick our own colors in the pictures we produce,” said Dr. Larry W. Esposito, a professor of Astrophysical and Planetary Sciences at the University of Colorado and UVIS Principal Investigator. “No person has ever seen ultraviolet light, although some butterflies can. Our pictures may thus represent a ‘butterfly’s-eye view’ of the Saturn system.”

Click the image to access a higher-resolution image on ESA’s Flickr page, and read more about the Cassini mission here.

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