Category Archives: Saturn’s Moons
By now you probably know about the lakes of liquid hydrocarbons on Titan. Thanks to Cassini, we know that Saturn’s largest moon is the one other place in the solar system where liquid can be found in stable amounts on the surface, except that it’s not water like we have here on Earth, but rather liquid methane. (Thank you for not smoking!) Now, radar measurements by Cassini show that Titan’s lakes are nearly all found in one 600 x 1100-mile region around its north pole — a true “land o’lakes!”
The animation above, made up of colorized radar data acquired over the past 9 years that the spacecraft has been in orbit around Saturn, takes us on a flyover tour of Titan’s northern lakes region. Fasten your seat belts!
A combination of exceptionally clear weather, the steady approach of northern summer, and a poleward orbital path has given Cassini — and Cassini scientists — unprecedented views of countless lakes scattered across Titan’s north polar region. In the near-infrared mosaic above they can be seen as dark splotches and speckles scattered around the moon’s north pole. Previously observed mainly via radar, these are the best visual and infrared wavelength images ever obtained of Titan’s northern “land o’ lakes!”
(But don’t even think about going swimming in these lakes — they’re filled with liquid METHANE, nearly 300 degrees below zero!)
It’s been thought for some time that Saturn’s largest moon Titan has a complex internal structure consisting of multiple layers of ice and liquid water. At one point it was even suggested that there are water ice “cryovolcanoes” on Titan, where watery slush oozes to the surface and freezes solid in the moon’s 270-degree-below temperatures, in very much the same way that liquid rock does on Earth. Now, thanks to recent gravitational observations by Cassini (and who else?) some researchers think that Titan’s icy shell may be much thicker in places than once thought, making the existence of ice volcanoes and Earthlike plate tectonics much less likely.
What looks like a single open-quote (or backwards comma) is really Saturn’s two-toned moon Iapetus, seen here in RGB composite color made from raw images acquired by Cassini on Aug. 30 from a distance of about 1.5 million miles.
With a leading side stained a dark reddish hue and a trailing side bright white, the 914-mile-wide Iapetus (eye-AH-peh-tus) is — almost literally — the yin-yang of Saturn’s family of moons.
The color variation on Iapetus is due to the fine coating of dark material that falls onto its leading hemisphere, possibly sent its way by smaller, distant Phoebe. This dark coating of dust causes that half of Iapetus’ surface to warm up ever-so-slightly-more than the other, making the water ice evaporate and redepositing it on the other side. This in turn just reinforces the whole cycle…a positive feedback loop.
Image: NASA/JPL/Space Science Institute. Composite by Jason Major.
Here’s a particularly nice view of Saturn backlit by the Sun, captured by Cassini while on the ringed planet’s night side on August 12, 2013. Titan is visible at the upper right, its thick atmosphere scattering sunlight into a nearly-complete ring around it.
The color-composite above was assembled from raw images captured in red, green, and blue color filters. Thanks to Cassini and the imaging team at the Space Science Institute in Boulder, CO for the opportunity to share another fantastic vista from Saturn!
Image: NASA/JPL-Caltech/SSI. Composite by Jason Major.
Saturn’s largest moon Titan has often been likened to a primordial Earth, with its thick atmosphere, changing weather patterns, and — most intriguing of all — vast amounts of liquid on its surface in the form of lakes, streams, and rivers. One big difference though: nearly ten times farther from the Sun than we are, temperatures on Titan are a chilly 290 degrees below zero (F) and so the liquid isn’t water, it’s methane… what’s called natural gas on Earth.
Still, methane does a good job replacing water in Titan’s own version of a hydrologic cycle. Methane rain falls to fill streams, carving gullies and canyons through the frozen landscape (where water is harder than rock) and eventually filling methane lakes and seas — some as large as our Great Lakes! Cassini has found evidence of Titan’s lakes in both repeated radar scans as well as visible-light images… but what hasn’t been found yet, strangely enough, are waves on the surfaces of these lakes. If they are indeed liquid methane, and Titan has weather capable of creating rain and sculpting dunes, then why are these enormous lakes so incredibly flat?
As seasons slowly change, Cassini will find out the answer.
Scientists working with data from NASA’s Cassini mission have confirmed the presence of a population of complex hydrocarbons in the upper atmosphere of Saturn’s largest moon, Titan, that later evolve into the components that give the moon a distinctive orange-brown haze. The presence of these complex, ringed hydrocarbons, known as polycyclic aromatic hydrocarbons (PAHs), explains the origin of the aerosol particles found in the lowest haze layer that blankets Titan’s surface. Scientists think these PAH compounds aggregate into larger particles as they drift downward.
“With the huge amount of methane in its atmosphere, Titan smog is like L.A. smog on steroids.”
– Scott Edgington, Cassini deputy project scientist