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kottke.org posts about saturn

The intricate wave structure of Saturn’s rings

posted by Jason Kottke   Sep 07, 2017

Saturn Waves by Cassini

On one of its final passes of Saturn, the Cassini probe captured this image of a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave. The waves are generated by the motion of Janus, one of Saturn’s smaller moons.

This wave is remarkable because Janus, the moon that generates it, is in a strange orbital configuration. Janus and Epimetheus (see “Cruising Past Janus”) share practically the same orbit and trade places every four years. Every time one of those orbit swaps takes place, the ring at this location responds, spawning a new crest in the wave. The distance between any pair of crests corresponds to four years’ worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades’ worth of the orbital history of Janus and Epimetheus. According to this interpretation, the part of the wave at the very upper-left of this image corresponds to the positions of Janus and Epimetheus around the time of the Voyager flybys in 1980 and 1981, which is the time at which Janus and Epimetheus were first proven to be two distinct objects (they were first observed in 1966).

The photograph is also an optical illusion of sorts. The rings appear to be getting farther away in the upper lefthand corner but the plane of the photograph is actually parallel to the plane of the rings…it’s just that the wavelength of the density wave gets shorter from right to left.

Update: Here are those density waves converted into sound waves. The first set sounds like an accelerating F1 car.

Two Saturnian moons, lined up

posted by Jason Kottke   Jan 06, 2016

Saturn Two Moons

The Cassini spacecraft took a photo of two moons of Saturn, Tethys and Enceladus, beautifully aligned with each other. The cosmic ballet goes on. (via slate)

11 years of Saturn photos from the Cassini probe

posted by Jason Kottke   Nov 20, 2015

The Cassini probe, launched from Earth in 1997 (six months before I started publishing kottke.org), has been taking photos of Saturn and its moons for 11 years now. The Wall Street Journal has a great feature that shows exactly what the probe has been looking at all that time. (Note: the video above features flashing images, so beware if that sort of thing is harmful to you.)

Cassini sippin’ on Enceladus

posted by Jason Kottke   Oct 28, 2015

Whoa, how have I not heard about this before today: the Cassini spacecraft is going to dive through a jet of water erupting from Enceladus, a Saturnian moon.

Discovering life was not on the agenda when Cassini was designed and launched two decades ago. Its instruments can’t capture microbes or detect life, but in a couple of dozen passes through the plumes of Enceladus, it has detected various molecules associated with life: water vapor, carbon dioxide, methane, molecular nitrogen, propane, acetylene, formaldehyde and traces of ammonia.

Wednesday’s dive will be the deepest Cassini will make through the plumes, only 30 miles above the icy surface. Scientists are especially interested in measuring the amount of hydrogen gas in the plume, which would tell them how much energy and heat are being generated by chemical reactions in hydrothermal vents at the bottom of the moon’s ocean.

That’s pretty crazy…it sounds like science fiction. NASA is doing a wonderful job producing great science with the lean budgets they are given.

Hydrothermal hints of the potential for life on Enceladus

posted by Jason Kottke   Mar 12, 2015


Two teams of NASA scientists have discovered evidence that hydrothermal vents on the Saturnian moon of Enceladus show signs of “active hot-water chemistry”. Why is that exciting? Because similar chemistry occurs deep in the Earth’s oceans *and* can support life. Phil Plait explains.

We see these vents in the ocean bottom on Earth, too. The water there is very hot, heated by tectonic processes inside Earth’s crust. It brings up minerals and nutrients, and life thrives there. A lot of the processes are the same as what’s imagined is happening on Enceladus; minerals are dissolved in hot water that spews up into the cold ocean, precipitating out. A lot of it is sulfur based, but amazingly life exists there anyway. The environment is highly toxic to humans-huge pressure, boiling water near the vents, freezing a bit farther away, and loaded with icky chemicals-but as a scientist once said, “Life finds a way.”

Between the evidence of past flowing water on Mars, Titan’s hydrocarbon lakes, Europa’s underground ocean, and Enceladus, it seems increasingly probable we’ll find life somewhere else in the solar system. That’s a pretty exciting prospect! (via @ericholthaus)

Update: It was also announced today that the Hubble has detected signs of a salty underground ocean on Jupiter’s moon Ganymede.

New observations of the moon using Hubble support this. Ganymede has a weak magnetic field, and, like on Earth, this generates an aurora-the glow created when high-speed subatomic particles slam into the extremely thin atmosphere. This glow is brightest in ultraviolet, and so astronomers used the Space Telescope Imaging Spectrograph (my old camera!) on Hubble to observe Ganymede. STIS is quite sensitive to UV and detected the aurora.

Now this part is a bit tricky: Jupiter has a powerful magnetic field as well, which interacts with Ganymede’s. As they do, the aurora changes position over time, moving up and down in latitude. However, the observations show that the aurorae do not change nearly as much as expected if Ganymede were solid. The best way to explain this is if the moon has a salty ocean under its surface. The ocean would have its own magnetic field and would resist the influence of Jupiter’s magnetic field, which in turn keeps the aurora steadier.

Turns out there’s water all over the place in the solar system. How about that?

The truth of science with your own eyes

posted by Jason Kottke   May 14, 2014

Clive Thompson recently saw the moons of Jupiter with his own eyes and has a moment.

I saw one huge, bright dot, with three other tiny pinpoints of light nearby, all lined up in a row (just like the image at the top of this story). Holy moses, I realized; that’s no star. That’s Jupiter! And those are the moons of Jupiter!

I’m a science journalist and a space buff, and I grew up oohing and aahing over the pictures of Jupiter sent back by various NASA space probes. But I’d never owned a telescope, and never done much stargazing other than looking up in the night unaided. In my 45 years I’d never directly observed Jupiter and its moons myself.

So I freaked out. In a good way! It was a curiously intense existential moment.

For my birthday when I was seven or eight, my dad bought me a telescope. (It was a Jason telescope; didn’t everyone have a telescope named after them?) We lived in the country in the middle of nowhere where it was nice and dark, so over the next few years, we looked at all sorts of celestial objects through that telescope. Craters on the Moon, the moons of Jupiter, Mars, and even sunspots on the Sun with the aid of some filters. But the thing that really got me, that provided me with my own version of Thompson’s “curiously intense existential moment”, was seeing the rings of Saturn through a telescope.

We had heard from PBS’s Jack Horkheimer, the Star Hustler, that Saturn and its rings would be visible and he showed pictures of what it would look like, something like this:

Saturn through a telescope

But seeing that with your own eyes through a telescope was a different thing entirely. Those tiny blurry rings, visible from millions of miles away. What a thrill! It’s one of my favorite memories.

Saturn without its rings

posted by Jason Kottke   Oct 17, 2013

Over at The Planetary Society, Emily Lakdawalla highlighted an image taken by the Cassini spacecraft of Saturn separate from its rings.

This enormous mosaic showing the flattened globe of Saturn floating amongst the complete disk of its rings must surely be counted among the great images of the Cassini mission. From Earth, we never see Saturn separate from its rings. Here, we can see the whole thing, a gas giant like Jupiter, separated at last from the rings that encircle it.

Taking this idea one step further, I removed the rings completely, along with the “ringlight” lighting up the night hemisphere, creating a more-or-less pure look of what Saturn would look like without its rings.

Saturn Without Rings

Larger version is available on Mlkshk.

Waltz Around Saturn

posted by Jason Kottke   Jul 25, 2013

Fabio Di Donato made this fantastic short film about Saturn using hundreds of thousands of images taken by the Cassini-Huygens spacecraft.

I love the editing technique employed here…the film feels like a silent short from the 1920s but also very contemporary. (via ★interesting)

Photograph from the surface of Titan

posted by Jason Kottke   Feb 05, 2013

So far, humans have taken photos from the surfaces of Earth, the Moon, Venus, and Mars. But I had no idea that a photo from the surface of Titan existed:

Titan Surface

The photo of the Saturnian moon was taken in 2005 by the Huygens probe, which was designed to land safely on the moon’s surface. From Wikipedia:

After landing, Huygens photographed a dark plain covered in small rocks and pebbles, which are composed of water ice. The two rocks just below the middle of the image on the right are smaller than they may appear: the left-hand one is 15 centimeters across, and the one in the center is 4 centimeters across, at a distance of about 85 centimeters from Huygens. There is evidence of erosion at the base of the rocks, indicating possible fluvial activity. The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. The assumption is that the “soil” visible in the images is precipitation from the hydrocarbon haze above.

And a special close-but-no-cigar award goes to the NEAR Shoemaker probe, which snapped this photo from about 400 feet above the surface of the near-Earth asteroid Eros:

Eros surface

The probe landed on the surface of Eros in February 2001 and transmitted usable data for about two weeks afterwards, none of which was photographic in nature.

Lovely watercolor maps

posted by Aaron Cohen   Mar 21, 2012

Well, now, this is gorgeous. Stamen Design overlaid watercolor textures on OpenStreetMap map tiles to show you what it would look like if your favorite watercolorist designed Google Maps.

Watercolor maps

It’s fun to scroll and scroll. (via @tomcoates)

And since we all could stand to look at more pretty things, watch this video of what different landscapes would look like if Earth had Saturn’s rings. (via @ianmurren)

Solar eclipse…by Saturn

posted by Jason Kottke   Sep 12, 2011

The Cassini spacecraft caught this remarkable photo of Saturn eclipsing the Sun in 2006.

Saturn eclipse

Click through for the big image and the massive image. If you look close can see the Earth in the image, for reals!

Saturn fly-by video

posted by Jason Kottke   Mar 15, 2011

There is no 3-D CGI involved in this amazing Saturn fly-by video…it’s made from thousands of hi-res photographs taken by the Cassini orbiter.

Wait for the full-frame full-color video starting at around 1:00. (thx, sam)

Imagining Earth with Saturn’s rings

posted by Jason Kottke   Dec 09, 2009

This video of what Earth would look like with Saturnine rings is pretty ho-hum, yeah, there’s a shot from orbit of the Earth with Saturn’s rings around it, and then BAM! here’s what it would look like at night in NYC:

Earth with Saturn's Rings

The view from Ecuador is pretty great too.

Update: Greg Allen wants an iPhone app that adds in Saturn’s rings to any shot you take with the camera.

With the combination of GPS and orientation data that’s baked in to so many digital photographs, it should be possible to create a filter — I hear the kids call them apps now — that automatically inserts properly positioned Saturn rings into any sky you want.

An augmented reality app would be nice too.

Quadruple transit of Saturn

posted by Jason Kottke   Mar 18, 2009

The Hubble Space Telescope captured four of Saturn’s moons crossing its face at the same time. (via cyn-c)

We’re still finding lots of new moons

posted by Jason Kottke   May 04, 2005

We’re still finding lots of new moons around the planets in our solar systems. Twelve new ones were just discovered around Saturn and Jupiter now has 63.

Amazing Hubble photo of Saturn’s rings

posted by Jason Kottke   Sep 16, 2003

Amazing Hubble photo of Saturn’s rings.