Bitter winter weather conjures visions of Saturn’s moon Titan

Saturn’s moons Titan (larger) and Rhea area a study in contrasts. Rhea is icy, airless, crater-gouged and 950 miles across. Titan is 3,200 miles in diameter (about half again as big as our moon) and enveloped in a dense atmosphere of nitrogen with a haze of hydrocarbons. The orange color comes from tar-like substances that form when methane is bombarded by ultraviolet light from the sun. Credit: NASA / JPL / Space Science Institute

We’ve got bitter cold weather on the way here in Duluth, Minn. with highs predicted around -7 F (-21 C) and lows at night of -20 F (-29 C). What better time to drop in on an even colder place, Saturn’s largest moon Titan. There the average daily high is 290 below zero (-179 C). In those frigid conditions, gases like ethane and methane, of which this moon has an abundance, rain down from the clouds and pool into hundreds of lakes, rivers and seas. From an orbiting satellite, you’d think you were looking at an aerial view of northern Minnesota.

Radar image from NASA’s Cassini orbiter showing a network of lakes in Titan’s northern hemisphere.  Titan’s atmosphere, which is about 95% nitrogen and 5% methane (natural gas) gives the moon a surface pressure 1.6x that of Earth. Credit: NASA/JPL

With a surface pressure 1.6 times greater than Earth, Titan’s atmosphere is thick enough to allow liquid hydrocarbons to exist on its surface. It’s the only known body aside from Earth with great quantities of exposed fluids. As for water ice, yes, Titan has that too, but it’s as hard as rock in such a brutal environment.

How about a swim in Titan’s Sea of Ligeia? This body of liquid hydrocarbons (ethane and methane) with a surface area bigger than Lake Superior, is located in Titan’s Arctic latitudes, has been artificially colored blue. Rivers of methane have carved many channels around its periphery. Credit: Antoine Lucas, Oded Aharonson & The Cassini Radar Science Team, Caltech/JPL/NASA

A new paper by scientists on NASA’s Cassini mission finds that blocks of hydrocarbon ice might dot the moon’s lakes and seas. Their presence is inferred by mixed readings of the lakes’ reflectivity. This is an interesting premise since solid methane ice is denser than the liquid variety and would be expected to sink. But scientists discovered that methane ice will float if the temperature is below the freezing point of methane (-297 F) and the ice contains at least 5% air absorbed from Titan’s atmosphere. Click HERE to read more on the topic.

Titan descent video. At the end at touchdown, you’ll see the shadow of the parachute – amazing!

Eight years ago this week, the European Space Agency’s battery-powered Huygens (HOI-gens) probe entered Titan’s atmosphere after departing the Cassini “mother ship” 3 weeks prior. Huygen ejected its back shell and heat shield and floated down by parachute through the moon’s orange haze. Two and a half hours later it made a slippery-slidey touchdown on the surface. Scientists had hoped it would land in an ocean, since it was made to float, but instead the probe struck terra firma (Titania firma?).

The Huygens probe landed on a soft, sandy riverbed. The rocks you see are most likely made of water ice. Credit: ESA/NASA/JPL/University of Arizona

On the way down, Huygens transmitted pictures of its descent as well as photos from the surface. Networks of streams were seen from the air; on the ground, eerie ice boulders are visible near to far under an orange sky. If there were ever a place you’d call alien, Titan would be it.

I expect once the cold sets in, all the extra clothing we vulnerable humans will don will give the place a similar otherworldly look. Cold weather and plenty of atmosphere – two things Titan and Duluth have in common. Maybe we should consider starting a “sister planet” program.

Here are a couple more videos of Huygens’ descent to Titan including one where you can heard winds buffeting the probe and another showing a brand new animation re-creating the craft’s final descent and peculiar landing. Enjoy!

Simulation of how the probe landed based on data sent back by Huygens.  

The winds of Titan – listen to the sound

21 Responses

  1. Wayne Hawk

    Aloha Astro Bob!

    In sitting here in absolute AWE with my mouth so wide open that my chin is actually touching the floor! Well, not so much the latter but definitely the former! How did we humans manage to gather the knowledge to DO ‘stuff’ like this? Incredible, absolutely incredible. Thank you for putting those videos on your blog (and your blog was nothing to “sneeze” at either).

    If memory serves me correctly, does it seem to you that the skies seem much more CLEAR (when it is near or cloudless) when the temperature falls to what we call “bitterly cold”? I used to do a LOT of walking when I was in high school since I didn’t feel the need to own a car since all my friends had one and would often choose to walk home from friends’ houses when it was rather late at night (for a high-schooler anyway). I’d almost always stop and gaze at the sky and be awestruck by those “northern lights” and the sheer number or “stars” in the sky. I’d never really be concerned about the below zero weather because I always dressed for it (I could have cared less for “fashion” then, as now) and would let myself “plop” down into a snow bank and just lie on my back for the better part of an hour watching the “show” that nature was giving me…and wondering, always wondering.

    Kind of a long way to ask a simple question, but I never thought to ask anyone else if they thought the same of those below zero night skies and I know you would notice something like that since you do what you do (and do it so well)! Was it just “me” or do you agree?

    Aloha For Now!

    1. Profile photo of astrobob

      Really enjoyed hearing about your walks and lack of fashion. Although there’s less humidity on subzero nights I’ve never been sure they’re noticeably clearer. I want to think that, but it’s so hard to tell because of the reflected light from snow cover in our area. We could find out by doing a limiting magnitude comparison now and during mid-summer from the same dark location.

      1. Giorgio Rizzarelli

        I was asking myself the same question just in these days. From my personal experience I have too the impression that winter nights are more clear (the few winter good weather nights we have here), but possibly it’s just an impression given by the fact that they’re darker (if at New Moon) because Sun is well under horizon. Of course this depends on latitude, and possibly local climate is important for the clearness. For example we here in Trieste (North East Italy) have a cold wind from Siberia, especially in winter, which cleans the air. The rare days after a rain and/or after wind calms down, we have the best nights.
        Indeed, on the other hand, if there’s snow it lends *much* reflected light. I realized it a couple of days ago when shooting that galaxy I quoted in another post.

  2. Giorgio Rizzarelli

    I like much analogies between other planets and Earth. Some times I think about the definition of habitability of a planet, which is given in terms of the similarity to Earth’s temperature range. On one side, worlds (moons) like Titan and Europa, which could both host life, show that the habitable zone could be redefined to be much wider. On the other hand it’s fun observing that Earth is not *much* habitable… in winter one can survive only in a special “spacesuit” or inside a “base”, while in summer for a long permanence on surface one needs protection from UV radiation. Even with very small eccentricity, Earth had temperatures ranging from -89°C to 57°C, or -129°F to 134°F… would we call this a really habitable planet? 😀

  3. H.Bob

    These are great videos AstroBob, thank you for finding and presenting them. Although the Titan moon landings were great, I also really enjoyed the first few seconds where the earth and our moon were shown to traverse across the sun, and then the rapid pan back to Saturn. It demonstrated scale very well. The microphone idea on the probe was great. Indeed, wouldn’t it be good to have a co tinuous live stream of a mars microphone or even a webcam. Can’t be that difficult these days! On the cold nights and clarity phenomenon, isn’t it the case that air molecules vibrate/move less in cold conditions and that produces slightly clearer skies? I thought that I had read that somewhere.

    1. Profile photo of astrobob

      I have not heard of vibration levels of air molecules producing clearer skies. If anything, I’d think the opposite, since cold air is denser than warm air due to less vibration. In any case, there are many decisive factors involved in how dark the sky the sky can be – humidity comes into play, light pollution, airglow and haze levels – to name a few.

      1. Bob Crozier

        I wonder if cold air (I mean significantly cold arctic air) seems ‘clearer’ because there is much less ‘twinkle’ (a good scientific term. eh?) caused by convection (heat rising) in the atmosphere? Usually arctic air is quite a bit drier too, isn’t it?

  4. Bob Crozier

    Is the final ‘segment’ of the “Titan descent video” (where we can see the shadow of the parachute pass by) actual video or an animated simulation? If it is actual video, then in the lower right corner of the video in that segment after the craft has landed, there seems to be something like heat waves affecting the image. Is that from some kind of thrusters? Also, if it is actual video, then I must say that they landed that craft *very* softly. There doesn’t seem to be any bump or bounce at all.

    How long did that probe function after it landed and is there anything that we learned from it that we did not know already?

    Last question for today: how does a small body like Titan (that I assume has much less gravity than we have on Earth) end up with an atmosphere heavy enough to produce 60% greater atmospheric pressure at the surface than what we have on Earth?

    Thanks Bob! Very cool post!

    1. Profile photo of astrobob

      That’s the real video imagery at the end. The only thing simulated is the pan around the area and the zoom to the sun in Titan’s sky. Huygens landed fairly softly onto muddy-sandy ground. You have a very good eye as far as those heat waves – those were generated by the bright lamp (yellow spot far right) shining on Titan’s surface. In the lower right, you’ll see tiny one-line descriptions describing what’s going on. The batteries were good for a few hours, but the probe sent data back for about 90 minutes. Huygens gave our first and to date only look at Titan from ground level and made in-situ measurements of atmospheric winds as well as taking the first clear photos of drainage channels and shorelines. That’s probably just a short list. Scientists think methane ice and nitrogen were incorporated in the moon when it formed in the early solar system and that it outgasses those materials to this day. Titan can hold onto its atmosphere not only because it’s fairly large for a moon but also because it’s far from the sun and not roasted like our moon.

  5. Lauren

    “On the way down, Huygens transmitted pictures of its descent as well as photos from the surface. Networks of streams were seen from the air; on the ground, eerie ice boulders are visible near to far under an orange sky. If there were ever a place you’d call alien, Titan would be it.’

    How is this so “alien” compared to our planet? We have large rivers with networks of hundreds tributaries, such as the Amazon River. In the artic, we have glaciers, huge ice masses. If you have a good view, not in the city, the sunset and sunrise are sometimes orange, as well as purples, pinks, reds, and other vibrant, deep, colors.
    I wasn’t able to view the videos on the computer I’m on, but I saw the picturesm and they were amazing.
    I question nearly everything in life. We may consider the moon Titan an alien, but wouldn’t any life from other planets onsider us the same?
    I imagine the planets forming were something like evolution. They started off as the same, enormous slow moving mass. Then smaller pieces began to break off, similar in style to icebergs and glaciers. They floated off in their own direction, and slowly adapted to being as far or as near to the sun as they were. The Earth, for example, was able to sustain life because it was just the right distance from the sun, not too close to burn up, but not so far away to freeze.

    I may not be very good at science, but I’m young and haven’t gone to very good schools in my few years. Science interests me a lot, the very core of everything. I’ve heard of the string theory, about possibly finding the very smallest unit in everything. I don’t know a whole lot about it, but there has to be something that caused that. And what caused that?? Science is like a merri-go-round, you think you’ve finally found the foundation of everything, and 20 years later, you find something even smaller with even better technology. A never ending cycle, like a circle. If there’s a God, who or what created him? There will always be questions, always a thirst to have them answered. And I would like to learn something big myself, eventually. Lkke I said, I may be young, but I question the very thing we call life. Would an animal as common as a house cat be considered alien siimply because we are not one organism? If we call a foreignor an alien, or even one of the moons of a different planet alien, who is to say we’re not alein to each other? We may find a form of fish on another planet. Would they be considered alien? I think so. But then again, what if we look closer into it and find it is closely related to a known species of fish here on Earth? Would it be considered alien then? Even the best scientist could not answer the questions I would ask.This is just a small portion. Give me an answer, I’ll come up with 3 more questions to ask about it. Science is a circle, trying to quench our thirst of knowledge.

    1. Profile photo of astrobob

      You could even argue we’re aliens to each other, since it’s so hard to get inside another person’s head at times. Though Titan does have similar land forms as Earth, there are key differences. Titan’s average temperature is nearly 300 below zero and its “water cycle” is based on liquid ethane and methane rather than water as on Earth. Its gravity is also considerably less than Earth’s and the atmosphere is filled with pink smog. That qualifies as alien from my perspective, but I agree that there are also striking similarities between Titan and our planet. Keep asking questions and I hope you continue your studies in science.

  6. Lauren

    Thank you, and I will keep studying science, as much as I can, I haven’t yet made it to college, but I do hope to study astrology one day.

    I do have another question, as well. Do we know what the center is made of yet, or no, not quite?? Such as underneath our watery surface, Earth is made up of mostly metals and rock down to the core.
    I’m not very updated with Titan, as I’ve been scanning the news for information about the Mars drones and pictures, but I’d like to learn more about Titan as well.
    Also, I apologize about the typos in my previous message. It was quite late, and I forgot to do a spell check before posting.

  7. Lauren

    Sort of like Earth’s core, except for the water ocean and the fact that there seems to be ice instead of liquid metals.
    Also, I was looking at how old the planets are. There doesn’t seem to be any difference between them, except when I googled Earth it said it said 2.54 billion years, instead of 2.5 billion years for most of the other planets. I know it is believed that the planets and other terrestial objects are aftermath of the Sun becoming a star. But, is that a fact, or a mere theory? Is it possible that there is several hundred light years difference between the planets, or were they created at the same time and google is wrong about the difference between Earth and the other planets beginnings?
    Just let me know if my questions bother you. I’ll just try to find out more on my own, elsewhere.

    1. Profile photo of astrobob

      The planets all formed about the same time about 4.6 billion years ago. Scientists study radioactive decay of of various elements found in meteorites, rocks from the moon and from the Earth’s crust to make the determination. The numbers you Googled are incorrect – not sure what they refer to but they’re definitely not the age of the planets.

          1. Profile photo of astrobob

            You may have misunderstood my earlier post. Just to be clear, meteorites are not radioactive in the sense of producing dangerous radiation. They may contain trace amounts of radioactive elements like uranium which decays to lead at a specific rate that allows scientists to determine the meteorite’s age. No meteorite I’ve ever held or heard of produces enough radiation through decay to worry about. Another common element used for dating is potassium, which decays into argon.
            Mars rocks have different ages and compositions from moon rocks and Earth rocks though all three have similarities. Many moon and Mars rocks resemble igneous rocks that form when magma or lava solidifies. Earth has a great many igneous rocks. If you ever come to the north shore of Lake Superior, they’re everywhere.

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