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Liquid Methane in Titan’s Canyons

It was in 2012 that Cassini data showed us the presence of the river system now called Vid Flumina, which empties into Titan’s Ligeia Mare after a journey of more than 400 kilometers. Given surface temperatures on this largest of Saturn’s moons, researchers assumed liquid methane would be the key player here. The question was whether the river — and the eight canyons that branched off from it along its course — were still filled with liquid or long dry.

Vid-Flumina-195x1024

Now we have the answer, thanks to new work from Valerio Poggiali (La Sapienza University, Rome) and colleagues. Using radar signals bounced off Titan’s surface in May of 2013, the researchers probed the deep gorges near Titan’s north pole and were able to distinguish rocky material from smooth liquid. We’re clearly looking at a surface that is actively eroding, one with striking comparisons to the landscapes of Utah and Arizona as well as the Nile River gorge.

Key to the work here is the use of Cassini’s radar as an altimeter, measuring the height of features on the surface. Poggiali and team were able to use the altimetry data in combination with previous radar imagery of the area to analyze the Vid Flamina channels. Radar returns from the channels are highly reflective, producing a telltale glint, and the radar backscatter in relation to nearby terrain implicates smooth surfaces. From the paper:

…we interpret these smoothness constraints as requiring liquid surfaces. This represents the first direct detection of liquid-filled channels on Titan. Furthermore, channels exhibit canyon-like morphology, with the liquid surface elevations of the higher-order tributaries of the Vid Flumina network…occurring at the same elevation as Ligeia Mare. We also find lower order tributaries with liquid surface elevations above the level of Ligeia Mare, consistent with elevated tributary networks feeding into the main channel system.

The canyons branching off from Vid Flumina are less than a kilometer wide, with walls as high as 570 meters. They were likely carved by the liquid methane as it drained into Vid Flumina, a process we see on Earth in the shaping of river gorges. These are steep walls, rising as sharply as 40 degrees. What remains unknown is the age of the processes at work here, and the depth of the liquid methane. What we can assume is that the presence of liquid in these canyons reflects a process of canyon formation that is ongoing on this active geological surface.

Image: Liquid methane and ethane flowing through Vid Flumina, a 400-kilometer long river often compared to Earth’s Nile River, is fed by canyon channels running hundreds of meters deep. Credit: NASA, JPL-Caltech, Agenzia Spaziale Italiana.

Such steep clefts in Titan’s landscape could be the result of several processes including terrain uplift and changes in sea level. This JPL news release draws comparisons with the Grand Canyon, where rising terrain caused the Colorado River to cut deeply into the landscape below over a timespan of several million years. But canyons formed from changes in water level are also found on Earth, as is evident at Lake Powell, a reservoir that straddles the border between Arizona and Utah. Here, the Colorado’s rate of erosion increases when the water level in the reservoir drops. On Titan, both process may be in play.

“It’s likely that a combination of these forces contributed to the formation of the deep canyons,” says Poggiali, “but at present it’s not clear to what degree each was involved. What is clear is that any description of Titan’s geological evolution needs to be able to explain how the canyons got there.”

canyon

Image: NASA’s Cassini spacecraft pinged the surface of Titan with microwaves, finding that some channels are deep, steep-sided canyons filled with liquid hydrocarbons. One such feature is Vid Flumina, the branching network of narrow lines in the upper-left quadrant of the image. Credit: NASA/JPL-Caltech/ASI.

We have other channels to study on Titan, and many may be hidden below the resolution of the Cassini instruments. But bear in mind as well that when the Cassini mission ends on September 15 of next year, we will have used its radar in imaging mode to cover a total area of 67 percent of the surface. That’s a triumph for the mission, but also a reminder of how much we leave unseen. No matter how successful the mission, it always points to what needs study next.

The paper is Poggiali et al., “Liquid-filled canyons on Titan,” published online by Geophysical Research Letters 9 August 2016 (abstract).

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Comments on this entry are closed.

  • RobFlores August 11, 2016, 18:47

    This is great work, what a tourist ride that rafting down those canyons,
    I guess Bonestell’s drawings of Rugged moons are very true on TITAN.
    Once you look at that terrain, how can you even think of Lunar terrain as
    dynamic. Even Mars looks a bit dull in comparison.
    If I understand correctly, Titan is not as “wet” with methane as predicted.
    There was supposed to be a global ocean. But it is apparently too warm for full methane seas. Since the Sun was substantially cooler a few billion years ago there may have been methane seas in the past, but we maybe looking at time epoch for Titan where Methane is beginning to permanently be in gaseous form, leaving only true H20 Ice as the surface’s main substance.

  • Mike Fidler August 11, 2016, 22:38

    I remember seeing this despeckling technique last year but they have been doing it on more of the images, much better perspective!

    A new way to view Titan: ‘Despeckle’ it.

    http://phys.org/news/2015-02-view-titan-despeckle.html
    http://www.nasa.gov/jpl/cassini/pia19051
    http://www.titanexploration.com/TitanImages2015Plus/TitanImages2015.htm

  • ljk August 12, 2016, 8:52

    Titan does have a global ocean of liquid water under its surface:

    http://www.skyandtelescope.com/astronomy-news/titans-latest-twist-ahiddenocean/

    Why we are not sending major expeditions to that amazing alien world just shows how messed up human priorities are. Just as with interstellar travel, we have the technology and the knowhow but people would rather focus on the Kardashians or how their fantasy football team is doing. And of course many of those people in charge of countries and corporations make sure that billions are unable to focus on much else besides everyday survival.

    While I am talking about sending deep space probes to the Saturn system, we also need to be examining this world, the one that looks like an egg!

    http://www.planetary.org/blogs/emily-lakdawalla/2012/05211206.html

    There are no excuses not to be exploring and colonizing the Sol system, then the galaxy.

    • Steve August 29, 2016, 12:07

      Absolument d’accord avec votre commentaire ! We should increase at once the budget of space exploration at least tenfold, probably more. We may have a narrow window of opportunity to do this before we are prevented by war, chaos, authoritarian regimes, economic collapse or else … This is now (within the next couple of years?) or never

  • djlactin August 12, 2016, 13:41

    On Earth, with liquid water, thermodynamic considerations mean that lipids assemble into spheres that consist of a lipid-lipid bilayer surrounding a sphere that surrounds water and that is surrounded by water. This arrangement is the basis of the cell, and of life. I wonder whether some analogous process could yield enclosed spheres in methane. Does anybody have sufficient biochemical/physical skllls to solve this problem?

    • Michael August 12, 2016, 17:31

      Might help, but even if there is life on Titan it is so cold any life would be very, very slow indeed.

      http://www.iflscience.com/space/template-methane-based-life-forms-titan/

      • Rob Henry August 14, 2016, 21:55

        That old chestnut again! Do you really think that life on Titan would be glacial? Well consider this… Most life on Earth (ie most of its biomass), is endolithic, much of it living in hotter environments than our more familiar surface life (some even >100C). There metabolic rates are always three or four orders of MAGNITUDE less than our extravagant surface forms.’How can this be?’ I hear you ask. Its simple… For life, reaction rates are set to an evolutionary optimum, by special catalysts called enzymes.

        Sure, for forms on Titan, intermediate metabolism will be based on organic free radicals, probably carbenes, of which we know very little, because they are unstable at our temperatures. However, poorly studied doesn’t mean that they won’t work perfect, and with similar specificity to more familiar biochemicals, except at 93K.

        I also note that diffusion rates will be slower – only 60% those on Earth, but here’s the killer… Free radicals have magnetic fields! Combine that with a charge, and enzymes can break the diffusion limit, by using these fields to guide the substrate to the reaction centre. On Earth, superoxide dismutase does exactly that, and is the only enzyme I know of that can break the limit!

        Doesn’t that just make you think there could be biochemists on Titan right now, quietly dismissing interest in life on Earth, because it is too hot for free radical intermediate metabolism, and as such, life would be diffusion limited, making it too slow to evolve higher forms.

        • Eniac August 16, 2016, 20:25

          Well said!

        • ljk August 17, 2016, 10:36

          What if Titan itself is alive and being billions of years old, operates at its own pace which only seems glacial to humans because our lifespans are the cosmic equivalent of mayflies? Plus our understanding of what is and could be alive is still so very parochial? We keep thinking of life on Titan being in those ethane lakes, but what if we are literally missing the forest for the trees?

          The overused phrase “That’s no moon!” could take on a whole new meaning.

          Yeah, I went there.