Cassini Week: Goodbye Cassini

On September 15, 2017, Cassini’s extraordinary, decades-long mission ended. The discovery machine sent back its final transmissions before vaporizing within Saturn’s atmosphere. Its atoms now a part of the planet that it put into such sharp focus for us. It marked the end of an era.

The past week has been bittersweet. I’ve spent many hours remembering and sharing some of my favorite Cassini images. I’ve only posted a small fraction of my favorites, and every time I hit the publish button I’d remember another image that I wish I had included. I could devote this entire blog to sharing images and discoveries that we owe to Cassini and never run out of content. The robot was truly remarkable.

I’ve saved my favorite image for today’s post, as I wrap up Cassini Week.

The ringed beauty, Saturn.

The ringed beauty, Saturn – Credit: NASA/JPL/Space Science Institute

This image blew me away the first time I saw it. It’s an image seared into my mind and one I’ll never forget. But there’s more to it than just what you see at first glance. There’s a deeper meaning to be uncovered upon closer inspection.

Look closer at the image above. Click on it; look at it in full screen. On the left side, between Saturn’s brighter main rings and the G ring is a pale blue dot. It’s the same pale blue dot that Carl Sagan waxed poetically about nearly 30 years ago, when we first saw our home planet from a similar perspective.

“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.

The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there…

There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”

Sagan’s words have never rang more true.

Cassini, along with all of the other instruments of science, do more than just teach us about the subjects of their attention. They teach us about ourselves. They put our infinitesimally small corner of the Universe in perspective. Cassini showed us worlds we could have hardly imagined. Each discovery making the Universe a little larger, a little more dynamic.

For some, that might make you feel small. Personally, I don’t think that’s a bad thing. It puts our more minor inconveniences and frustrations in perspective. It’s a reminder of how far we’ve come as a species, how fortunate we are to live our lives at such an exciting time.

And, it gives us the tiniest glimpse of the potential of our future.


Cassini Week: Artistic Imagery

We’ve all marveled over Cassini’s images of the Saturn system for more than a decade. Saturn is a truly dynamic place, surrounded by equally dynamic worlds. But Cassini’s images did more than just capture images of these distant places; it created art. Breathtaking ‘landscapes’, magnificent portraits, and photographs perfectly timed and framed. Cassini has all of the skill and talent of a master photographer, with special thanks to its imaging team back on Earth. Below are just a few of my favorite Cassini photos.

Dione, Saturn, Rings, and Enceladus

Dione, Saturn, Rings, and Enceladus – Credit: NASA/JPL-Caltech/SSI

Quintet of Moons

Quintet of Moons – Credit: NASA/JPL-Caltech/Space Science Institute

Janus (179 kilometers, or 111 miles across) is on the far left. Pandora (81 kilometers, or 50 miles across) orbits between the A ring and the thin F ring near the middle of the image. Brightly reflective Enceladus (504 kilometers, or 313 miles across) appears above the center of the image. Saturn’s second largest moon, Rhea (1,528 kilometers, or 949 miles across), is bisected by the right edge of the image. The smaller moon Mimas (396 kilometers, or 246 miles across) can be seen beyond Rhea also on the right side of the image.

Dione, Epimetheus, and Rings

Dione, Epimetheus, and Rings – Credit: NASA/JPL-Caltech/Space Science Institute

Just one more day until Cassini’s Grand Finale. Stay tuned for more Cassini Week celebration.

Cassini Week: Rings

In the famous words of the 21st Century philosopher, Beyoncé, “if you like it then you shoulda put a ring on it”.

In that case, the Universe must have really liked Saturn.

While all of the gas giants in our solar system have rings, Saturn’s are by far the most prominent and celebrated. And while humans have been admiring Saturn’s rings for centuries (when Galileo first discovered them, he described them as Saturn’s ears), it was Cassini that brought them into razor-sharp focus.

Shadows cast on Saturn's A ring.

Shadows cast on Saturn’s A ring. – Credit: NASA/JPL/Space Science Institute

Several sets of shadows are cast onto the A ring in this image taken about a week after Saturn’s August 2009 equinox.

Near the middle of the image, shadows are cast by vertically extended clumps in the kinky, discontinuous ringlets of the Encke Gap in the A ring. These clumps are casting shadows approximately 275 kilometers (170 miles) long, implying a clump height about 600 meters (2,000 feet) above the ring plane.

In the middle left of the image, the waves created by Daphnis (8 kilometers, 5 miles across) on the edge of the Keeler Gap cast shadows on the A ring that are about 450 kilometers (280 miles) long, indicating waves that rise about one kilometer above the ring plane. The moon itself is not visible at this resolution, but it, too, orbits in the Keeler Gap of the A ring. Daphnis has an inclined orbit, and its gravitational pull perturbs the orbits of the particles of the A ring forming the Keeler Gap’s edge and sculpts the edge into waves having both horizontal (radial) and out-of-plane components. Material on the inner edge of the gap orbits faster than the moon so that the waves there lead the moon in its orbit. Material on the outer edge moves slower than the moon, so waves there trail the moon.

The Janus 2:1 spiral density wave

The Janus 2:1 spiral density wave – Credit: NASA/JPL-Caltech/SSI

This view from NASA’s Cassini spacecraft shows a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times.

Propeller in Saturn's A Ring

Propeller in Saturn’s A Ring – Credit: NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini spacecraft captured these remarkable views of a propeller feature in Saturn’s A ring on Feb. 21, 2017. These are the sharpest images taken of a propeller so far, and show an unprecedented level of detail. The propeller is nicknamed “Santos-Dumont,” after the pioneering Brazilian-French aviator.

Have you heard of Saturn’s propellers before? They’re the result of a very small moon, unseen in the photo above, disturbing ring material. They offer a unique opportunity for researchers to track the orbits of unseen objects that are embedded within a disk of material.

Epimetheus and smog-enshrouded Titan, with Saturn's A and F rings stretching across the scene.

Epimetheus, Titan, and rings. – Credit: NASA/JPL/Space Science Institute

Cassini delivers this stunning vista showing small, battered Epimetheus and smog-enshrouded Titan, with Saturn’s A and F rings stretching across the scene.

Stay tuned for more, as we continue our Cassini Week celebration.

Sunday Matinee – NASA at Saturn: Cassini’s Grand Finale

The final chapter in a remarkable mission of exploration and discovery, Cassini’s Grand Finale is in many ways like a brand new mission. Twenty-two times, NASA’s Cassini spacecraft will dive through the unexplored space between Saturn and its rings. What we learn from these ultra-close passes over the planet could be some of the most exciting revelations ever returned by the long-lived spacecraft. This animated video tells the story of Cassini’s final, daring assignment and looks back at what the mission has accomplished.

Cassini’s Grand Finale

On September 15, one of the most fruitful space missions ever imagined will come to an end. After two decades in space, Cassini’s fuel supplies are close to being depleted. To avoid contaminating one of Saturn’s moons, including a pair that could harbor life–Enceladus and Titan–the decision was made to retire Cassini into Saturn’s atmosphere. Up until contact between the orbiter and Earth is lost, Cassini will continue to study our beloved ringed planet. New insight will be gleaned from this mission that’s only made possible by Cassini’s fatal approach to the gas giant. Among the data to be collected:

  • The spacecraft will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the planet is arranged internally, and possibly helping to solve the irksome mystery of just how fast Saturn is rotating.
  • The final dives will vastly improve our knowledge of how much material is in the rings, bringing us closer to understanding their origins.
  • Cassini’s particle detectors will sample icy ring particles being funneled into the atmosphere by Saturn’s magnetic field.
  • Its cameras will take amazing, ultra-close images of Saturn’s rings and clouds.

Cassini launched on Oct. 15, 1997. After a seven-year journey the orbiter arrived at Saturn, carrying the European Space Agency’s Huygens probe. In 2005, the probe successfully landed on Saturn’s largest moon, Titan.

Quick facts about Titan:

  • Titan is the solar system’s second largest moon.
  • It’s the only moon in our solar system that has cloud systems and a dense, planet-like atmosphere.
  • Titan has liquid hydrocarbon lakes, mountains, and seasonal weather patterns.

For 13 years, Cassini has orbited Saturn and provided us with fascinating information about, not just the planet, but its intricate ring system and many moons.

Cassini mission overview infographic

Cassini mission overview infographic – Click for larger version – Source: NASA/JPL

In addition to the important scientific data that was collected by Cassini, are the breathtaking images that have been collected: storms and aurorae on Saturn, detailed views of the worlds that are Saturn moons, and remarkable visions of Saturn’s sensational rings.

For the next week, we celebrate Cassini’s achievements.

Still from the short film Cassini's Grand Finale, the spacecraft is shown diving between Saturn and the planet's innermost ring.

Still from the short film Cassini’s Grand Finale, the spacecraft is shown diving between Saturn and the planet’s innermost ring. – Credit: NASA/JPL-Caltech

What’s Up: September 2017

It’s September and a wonderful time to enjoy the night sky. In northern latitudes, the length of night is generally outpacing the upcoming winter chill. Spring and Fall are great times to become reacquainted with the cosmos.

Here’s a brief run-down of what to expect in the September skies (note: this information is tailored to those of us in the Northern Hemisphere).

What’s that planet?:
If it’s in the evening, it’s most likely Jupiter. If it’s in the morning, you might be seeing Venus, Mercury or Mars.

This month, Jupiter is its bold, bright self, but it’s tracking fairly close to the Sun and setting in the southwest. You’ll see it shortly after sundown, earlier and earlier the further north you are. In October, Jupiter will be outside of our view until its return in November. On September 21 and 22, Jupiter will appear very near to a thin crescent Moon. Saturn is also up during September nights, though you’ll want to consult a star chart or skymap app to find it due to it being hard to distinguish from stars. Speaking of Saturn, September 15 marks the grand finale of the Cassini spacecraft. After 20 years of astonishing service, Cassini will plunge into Saturn’s atmosphere and end one of the most successful space missions imagined.

On September mornings, keep an eye out for Venus, Mars, and Mercury. Venus is hard to miss, it’s the brightest object in the sky following the Sun and Moon. Keep an eye to the east about two hours before sunrise (closer to sunrise the later we get into the month) for our bright sister planet.

If you’re fortunate enough to live on the mid-northern latitudes, you might get to witness a fantastic conjunction of Mercury and Mars. (If you’re as far north as Alaska, you’ll need a clear view of the horizon.) On September 16, Mercury and Mars appearing extremely close to each other in the morning sky. Use this website to get a custom report for your viewing location.

If you need help finding out when a planet rises and sets for your location, this website is fairly indispensable.

Happy viewing!