Planet Pailly

Titan has held a special place in the hearts and minds of Sci-Fi authors for decades. Initially it was because the thick, opaque atmosphere made Titan a moon on mystery. No one knew what might be hidden on the surface. It seemed like the kind of place where anything could happen.

Unraveling Titan’s mysteries has only increased this large moon’s allure. Chemically speaking, Titan couldn’t be more alien to us, yet it looks eerily familiar. The lakes and rivers, mostly situated in the northern hemisphere, bear an uncanny resemblance to features seen on Earth.

A world both familiar yet alien: sounds like the perfect setting for a science fiction adventure to me. So what would it be like to set foot on the surface of Titan? In 2005, the Huygens probe (a joint mission by NASA and ESA) landed on the surface of Titan, collecting data all the way through its descent and for about 90 minutes after touchdown.

Based on measurements by two impact penetrometers, it seems Huygens landed on a surface of hardened crust atop a layer of softer, perhaps moister material. Scientists at the time compared it to crème brûlée. Of course, this crème brûlée is infused with methane, ethane, butane, etc; so it probably doesn’t taste very good.

Assuming the Huygens landing site is typical of surface conditions in general (which it may or may not be), walking on Titan might feel a little like slogging through mud. The hardened upper crust is probably not thick enough to support your weight, even in the reduced gravity.

Regarding weather, it doesn’t so much rain on Titan as drizzle. Picture a gloomy, overcast day here on Earth with the air heavily saturated by mist. Now drop the temperature to -180 C (-290 F), turn the clouds from grey to dull orange, and change the misty, drizzly precipitation from water to liquid methane. That would be normal weather conditions on Titan.

There is some evidence of heavier rainstorms from time to time, perhaps heavy enough to cause flash flooding, but this appears to be rare compared to the amount of rain and flooding we get here on Earth. I wouldn’t worry too much about this.

Today’s post marks the end of our month-long visit to Saturn and its moons. As the 2015 Mission to the Solar System continues, we can now turn our attention to one of the strangest, most enigmatic planets in the Solar System: Uranus.

Links

Titan Unveiled: Saturn’s Mysterious Moon Explored by Ralph Lorenz and Jacqueline Mitten.

Rare Rains on Titan from Astrobiology Magazine.

“The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ but ‘That’s funny…”

– Isaac Asimov

In the 1980’s, Voyager 1 and Voyager 2 flew past Saturn, collecting data and snapping lots of photos to send back to Earth. One of the features discovered during that mission was a near prefect hexagon-shaped cloud formation at Saturn’s north pole.

In 2009, the Cassini spacecraft confirmed that the hexagon was still there, apparently unchanged after 30 years, and began collecting more data and taking more pictures.

Scientists aren’t 100% sure what causes this hexagon (some wise thinkers on the Internet have proposed a connection to the satanic rituals of the Illuminati). The best theoretical model at the moment seems to be that differing wind speeds in Saturn’s atmosphere have generated a standing wave with six peaks and six troughs (on the sixth planet, making 666… Oh no! The Internet was right!)

Similar hexagonal standing waves have been created in the laboratory.

Researchers also created ovals, triangles, octagons, and other shapes using standing waves, suggesting that there may be more planets out there with geometric cloud formations in their atmospheres.

But the really important thing to know is that, based on infrared imagery, it appears the hexagon is rooted deep into Saturn’s interior structure. The hexagon’s rotation may directly correspond to the rotation of Saturn’s presumably solid, possibly metallic core.

If that’s true, then the hexagon may provide planetary scientists an easy way to study Saturn’s interior, and perhaps a way to learn about the interior structures of gas giants in general. All thanks to a rather odd, rather funny observation of Saturn’s north pole.

Links

Saturn’s Hexagon Recreated in the Laboratory from the Planetary Society.

Science Shot: Mysterious Hexagon May Reveal Length of Saturn’s Day from Science Magazine.

I owe one of Saturn’s moons an apology. Enceladus is on the shortlist of places in the Solar System that might support life, but I never took Enceladian life seriously. You see, Enceladus is really small. I mean really, really small. A mere 300 miles across.

For some time now, we’ve known Enceladus has liquid water beneath its surface. The cryovolcanos in the south polar region make it pretty obvious. You can see them erupting in the totally legit Hubble image above.

But how much water is there, and how long has it been liquid? Could an object so small and so far from the Sun really retain enough internal heat to support a vast, subsurface ocean similar to what we’ve found on Europa?

For the most part, the scientific literature has talked about a localized subsurface lake near the south pole or maybe just a tiny pocket of melt water. The kind of thing that might form periodically and then freeze solid again. This hardly sounds like a suitable environment for the evolution of life.

It was hard to believe in a vast subsurface ocean teeming with Enceladian microbes and Enceladian fish. Until now.

Just this month, an important new paper came out in the journal Icarus. It seems Enceladus rocks back and forth (“librates,” to use the technical term) a little too much to be solid all the way through. Something must be sloshing around inside, with the moon’s entire eggshell-like surface floating on top.

This discovery follows on the heels of another paper, published in July by Nature, which offered a global subsurface ocean as one of two possible explanations for an observed discrepancy in Enceladus’s cryovolcanic eruptions. The eruptions were occurring several hours after they should have according to previous models.

It’s interesting that not one by two scientific papers, each following different lines of research, came to almost the same conclusion. According to the paper in Nature, Enceladus might—just might—have a global subsurface ocean; and according to the Icarus paper, it totally does have an ocean, just like Europa.

None of this proves Enceladus has life, but that possibility seems a lot more credible in a global ocean than in tiny pockets of melt water.

So Enceladus, I’m sorry. I never should have doubted you.

P.S.: It’s still unclear how Enceladus maintains enough internal heat for its ocean. To quote the Icarus paper, “[…] a global ocean within Enceladus is problematic according to many thermal models […].” The best guess for now is that Saturn exerts more tidal forces on Enceladus than previously thought.

Links

Timing of Water Plume Eruptions on Enceladus Explained by Interior Viscosity Structure from Nature Geoscience.

Enceladus’s Measured Physical Libration Requires a Global Subsurface Ocean from Icarus.

What’s Inside Saturn Moon Enceladus? Geyser Timing Gives Hints from Space.com.

Enceladus: A Global Ocean from Centauri Dreams.

Imagine you’re a hotshot space pilot on approach to Saturn. You know perfectly well you’re not supposed to fly through Saturn’s rings. The rings are protected by an intergalactic trust. You could get in a lot of trouble.

Okay, if we’re doing this, let’s do it the awesome way! The thickness and density of the rings varies somewhat, so let’s aim for one of the main rings (which astronomers call the A-ring, B-ring, and C-ring). In fact, aim for the middle band of the B-ring. That’s one of the thickest, densest parts.

Saturn’s rings are a mix of stuff, including rock and organic compounds, but most of the material is water ice. According to one source I found, the rings are composed of 90 to 95% ice. Most of this ice is in the form of teeny, tiny crystals, so basically we’re flying into a vast expanse of snowflakes.

Some of these snowflakes are floating free. Others have clumped together, forming larger objects. In 2005, the Cassini mission beamed radio waves at Saturn’s rings. By seeing which wavelengths bounced back, scientists got a rough estimate of the sizes of these tiny and sometimes not-so-tiny objects.

In the B-ring, most of the objects we’ll encounter will be at least 5 centimeters in diameter. Many will be larger than that. Perhaps much larger. Unfortunately, the ring particles in the middle of the B-ring are so close together that virtually all of Cassini’s radio waves bounced back. So it’s hard to say how large individual objects might be in there.

I guess we’re about to find out!

Don’t panic. It seems objects in Saturn’s rings are continuously coalescing and disintegrating due to collisions with each other and interactions with Saturn’s gravity. That suggests these objects are merely loose rubble piles of tiny ice crystals. Collide with one, and it should just burst apart like a lightly packed snowball.

Still, you should probably slow down a bit. At your current velocity, collisions with even the tiniest speck of dust could puncture your spaceship’s hull.  Seriously.  You need to slow down!  Look out for the—!

Disclaimer: Today’s post is not intended as advice on whether or not you should attempt to fly through Saturn’s rings. If you decide to fly through Saturn’s rings, you do so at your own risk, and the author of this post cannot be held liable for any damages that may ensue.

Links

Cassini Radio Signals Decipher Saturn Ring Structure from NASA.

Particle Sizes in Saturn’s Rings from Astronomy Picture of the Day.

Saturn’s Rings from NASA Jet Propulsion Laboratory (great chart to help you identify each of Saturn’s rings).

Saturn Rapidly Creates and Destroys Its Moonlets from Discovery News.