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Of a Mountain on Titan

If Saturn’s inner moons are, as we discussed yesterday, as ‘young’ as the Cretaceous, then we have much to think about in terms of possible astrobiology there. But Titan is unaffected by the model put forward by Drs. Ćuk, Dones and Nesvorný, being beyond the range of these complex interactions. Huge, possessed of fascinating weather patterns within a dense atmosphere, Titan probably dates back to Saturn’s earliest days, in some ways a frigid ‘early Earth’ analog.

When my son Miles was a boy, we drove through the Appalachians on a journey that eventually took us into Canada. Somewhere in the Shenandoah Valley he commented on how insignificant the mountains seemed compared to what he was used to out west, where the Rockies dominate the sky. True enough, but of course the Smokies and the Cumberlands have their own tale to tell. Once monumental, they’ve fallen prey to wind and rain, ancient relics of once grander peaks.

The latest work on Titan from Cassini data now reveals something about similar erosion on Titan, where we have rain, lakes and seas, not to mention rivers cutting their way through the landscape. But Jani Radebaugh (Brigham Young University, Utah), who works with the Cassini radar team, notes that erosion on Titan is actually a much slower process than on Earth, thanks to Titan’s being ten times Earth’s distance from the Sun. There is just that much less energy to drive these processes in the thick atmosphere. See this JPL news release for more.

With Titan we have to think in terms of analogies. On Earth it’s water that freezes, thaws, vaporizes, providing a hydrological cycle that works its seasonal magic in terms of weather change. On Titan it’s methane that performs a similar function. Meanwhile, Titan’s water ice behaves much more like rock on Earth, an icy crust overlaying what is likely to be an ocean of liquid water — here the analogy is with Earth’s upper mantle. In both cases, these inner layers accommodate slow changes as mountains form and ranges begin to settle.

Radebaugh’s team used Cassini’s radar instrument to study the ridges known as the Mithrim Montes, among which is found the moon’s tallest peak, some 3337 meters high. “It’s not only the highest point we’ve found so far on Titan, but we think it’s the highest point we’re likely to find,” says Stephen Wall (JPL), deputy lead of the Cassini radar team. The results were presented at the 47th Lunar and Planetary Science Conference in Texas.

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Image: The trio of ridges on Titan known as Mithrim Montes is home to the hazy Saturnian moon’s tallest peak. The mountain, which has an elevation of 3,337 meters, is located midway along the lower of the three ridges shown in this radar image from NASA’s Cassini spacecraft. Credit: NASA/JPL-Caltech/ASI.

The view above was acquired on the T-43 flyby back on May 12, 2008 at an incidence angle of about 34 degrees. Remember that this is a radar image, which uses reflections scattered off the moon’s surface to see through the thick, opaque atmosphere. Dark areas indicate regions that are relatively smooth or otherwise absorb radar waves, while bright regions are rougher materials that scatter the beam. A ‘speckle’ pattern is an artifact of the technique — in this image, ‘despeckling’ methods were used to reduce the noise and produce clearer views.

Titan’s mountains don’t reach the heights we see in some of Earth’s ranges, but researchers hadn’t expected they would because the water-ice bedrock is softer than Earth’s rock. But it is significant that we find tall mountains here, an indication of active forces shaping the surface that are perhaps Titan’s response to tidal forces from Saturn, or perhaps cooling of the crust. Finding such ‘active zones’ in the crust tells us something about Titan’s history.

“As explorers, we’re motivated to find the highest or deepest places, partly because it’s exciting,” adds Radebaugh. “But Titan’s extremes also tell us important things about forces affecting its evolution. There is lot of value in examining the topography of Titan in a broad, global sense, since it tells us about forces acting on the surface from below as well as above.”

Titan’s highest mountains all seem to be close to the equator, with other peaks of a similar height being found within the Mithrim Montes (for Tolkien cognoscenti, the Mountains of Mithrim ran northwest from the Ered Engrin, dividing Dor-lómin from Mithrim, and that is as far as I go with Tolkien today). Other peaks are known in the Xanadu region. Learning more about the forces that formed them is now a priority for researchers probing Titan’s mysteries.

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Comments on this entry are closed.

  • RobFlores March 29, 2016, 15:53

    Aside from the goal of geophysical characterization of Titan by the research there is possibly another reason to find the high peaks or high
    plateaus on Titan. Placing a future permanent base there would be
    ease one POTENTIAL aggravation which can be more easily mitigated.
    At lower altitudes the Barometric pressure on Titan is around 1470 mb or so. at that pressure to have a safeguard against incursions from the outside atmosphere (in particular methane-ethane-cyanogen) you would want a positive pressure gradient of possibly 10%. While we think being a human base with a resulting 1610-20 mb pressure should not be harmful, I don’t know if anyone has tested human physiology under those conditions for months let alone years.
    At around 3.1km high the Barometric pressure on Titan is somewhat friendlier at 1260 mb with an additional 10% you would have around 1386 mb base pressurization. It would have the added value of making semi inflatable base modules somewhat easier to design (assuming the material can insulate and withstand Titans cold exterior).
    As a bonus, if turns out that these ice mountains have near by geysers of ammonia-water, it might be energy efficient to try and collect this “lose”
    ice materials BEFORE it gives up all it’s latent heat and becomes at hard as stone. (because there is ICE and there is super cooled ice under pressure)

  • Ashley Baldwin March 29, 2016, 19:43

    Thanks Paul.
    I sadly have a coloured map of Beleriand adorning my office wall at work. It is the subject of considerable debate though it doesn’t feature in LOTR directly .
    Titan and Saturn’s other moons could easily be mapped in considerable detail by the technology developed in various cometary and asteroid technology missions passed and yet to come. ESA missions like Rosetta produced the wonderful VIRTIS , visual and infrared thermal imaging satellite ( improved further by Dawn and Venus Express ) that along with the mass spectrometers of New Frontiers Osiris-Rex and its OLA, laser altimeter could accurately map Titan and other moons both mineralogically , spatially and topographically through any smog and much cheaper and higher resolution than radar .
    Just two or three instruments which combined with a decent imager ( I would love to see a combination of dim target LORRI from New Horizons and ultra high res telescope / camera HiRISE from MRO. Both long lasting , proven and fully developed so probably reasonably priced . These few instruments mean that Flagship science can now be deliverered by both the highly successful New Frontiers and Discovery programmes which MUST be continued in their current format or more often as the incremental breeding ground of new technology .
    With the U.S. Making Pu238 again hopefully an RTG will be offered as standard if required though solar arrays can now work out to Saturn ( which may be vital for power hungry HiRISE) . Time unfortunately is an object so the sooner we have a low cost heavy launcher the better then it’s Enceladus and Saturn in four years with a just a ten year return trip for even sample return LIFE , with two years in situ science too. How good would that be ? The NEAT ion drive might be offered too providing long term Cassini style multi flyby versions of ELF , maybe of more than one planet with a suitable Titan gravity assist . An Ice giant would be nice .
    With modern data compression even the four years return leg of LIFE alone would be filled with mission science .

  • P March 29, 2016, 20:00

    I for one would love to see more of Cassini’s radar dataset denoised like this, even if its just from an aesthetic pov. And what about that radar dark circular area south of the highest ridge? Impact feature? Cryovolcano? Daipir?

    P

  • Brett Bellmore March 31, 2016, 20:19

    A good deal of Earthly weathering is driven by two factors missing on Titan.

    First, water is almost unique in that it expands when it freezes. This leads to the freeze/thaw cycle where liquid water penetrates the tiniest crack, and then in freezing produces enormous force to wedge it open. Water isn’t going to do much thawing at Titan’s temperatures.

    Second, many rocks are chemically unstable when exposed to our atmosphere. I don’t see that happening much on Titan, either.

    So, VERY slow weathering.

  • Brett Bellmore March 31, 2016, 20:20

    Creep is probably a bigger factor.

  • Michael April 6, 2016, 9:43

    I vaguely remember a post about suspected cryo-volcanism changing a landscape near an island or shore, it is more likely an upwelling of material from the interior of Titan causing uplift and this mountain region as well. This should be more proof of a subsurface ocean.