Possible Cyrovolcanism on Titan

Today we are going to visit on of Saturn’s moons, Titan. Surrounded by a thick, orangey haze of an atmosphere, Titan isn’t very exciting when viewed by the eye, but peering past the haze with various scientific instruments shows a much more interesting story. In some ways Titan, the “Earth of the outer solar system”, is very Earth-like: there are dune fields, mountains, lakes and rainstorms. However, instead of water, there is liquid methane.
Titan, appearing as an orangy sphere, in front of Saturn. Saturn's rings are nearly edge on and appear to pierce through Titan; details of the rings can be seen as a shadow on Saturn. Image Credit: NASA/JPL-Caltech/Space Science Institute/J. Major. Astronomy Picture of the Day for July 3rd, 2012.
Titan, appearing as an orangy sphere, in front of Saturn. Saturn’s rings are nearly edge on and appear to pierce through Titan; details of the rings can be seen as a shadow on Saturn. Image Credit: NASA/JPL-Caltech/Space Science Institute/J. Major. Astronomy Picture of the Day for July 3rd, 2012.
Titan may even have its own version of volcanoes. Called cyrovolcanoes or ‘ice volcanoes’, these have melted or partially melted ‘magma’. In the case of Titan, this would likely be an ammonia-water mixture, perhaps mixed with methanol or other chemicals. Cyrovolcanoes are known to exist on Enceladus, another of Saturn’s moons, and perhaps have shaped Jupiter’s moons Europa and Ganymede, and Neptune’s moon Triton. The existence of cyrocolvanoes of Titan, however, is debated.  Perhaps cyrovolcanism has only happened once in the history of Titan, or perhaps it is periodic. Either way, there is not any proof.
That brings us to today’s article, “Cryovolcanism on Titan: New results from Cassini RADAR and VIMS” by  R. M. C. LopesR. L. KirkK. L. MitchellA. LeGall and a dozen others. RADAR and VIMS  (Visible and Infrared Mapping Spectrometer) both refer to instruments on the Cassini spacecraft orbiting Saturn . The article was published in 2013 in the American Geophysical Union’s Journal of Geophysical Research: Planets. These sixteen people examined sites on Titan that have been suggested to be cyrovolcanic in origin. Instead of going in with preconceived notions, they looked at each area with fresh eyes, carefully inspecting them for evidence for or against cyrovolcanism. Cyrovolcanism would explain the presence of certain elements of the atmosphere, but cyrovolcanic features can appear similar to fluvial (formed by a river) features. 
So how can you tell the origins of such things? There are several hints. If a hot spot, an extra-warm section often found under terrestrial volcanoes, is discovered on Titan, that would be a strong indication of at least the possibility of cyrovolcanism. None have been seen on Titan so far. There has also not been any noted changes on the surface. This does not mean there is no cyrovolcanism on Titan; it may mean that it has gone unseen (not all of Titan has been mapped), or that it is not a current process.
Many of the features on Titan suggested to be cyrovolcanic in origin involve features that appear to have been caused by some sort of liquid running across its surface. But was this cyrolava, or the liquid methane of Titan’s lakes and rivers? There are a few ways to figure this out. One: identify the source that the flow came from. A flow from a fissure or circular region is unlikely to be a river, for example. Secondly, note the topography. Cyrovolanic flows can have a variety of shapes and heights, but sedimentary flows will only pool in low-lying regions. Lastly, look at the pattern: fluvial flows often have dendritic patterns; the many branched system of waterways we are used to on Earth.
Multiple regions once suggested to be cyrovolcanic were found to not be of such origins when more closely examined with fresh data. Some features have too little data on them to be able to tell either way. Briefly, I present the features of Titan that are possibly, or more than likely, cyrovolcanic.
Tui Regio: the Tui Regio section of Titan has fluvial channels with nearby mountains. It also has a feature that looks like it could be a cyrovolcanic flow. There is not a lot of topographical data, and without that, the evidence given neither supports nor rules out cyrovolcanism. The authors called this ‘possibly cyrovolcanic’.
Hotei Regio: This area involves two low regions that could be paleolakes (ancient lakes, no longer with liquid) or a caldera (volcanic crater). Valleys that appear fluvial in nature are associated with nearby mountains, but there is no rule forbidding fluvial and cyrovolcanic features to occur together. There are also other flows that are higher than the fluvial features, and run the same height as each other. The authors left this as fluvial, but with possibly cyrovolcanic features that are topographically high.
Western Xanadu Region: This was put in the category of possibly cyrovolcanic. It has what appears to be overlapping flows. It has a similar form to the Hotei as well as Sotra (see below), but there is not a lot of data. The authors cannot say for sure either way.
A still from a video that features a flyover of the Sotra Patera region, along with an explanation of its importance. A link to this video can be found in the bibliography. Credit: NASA/JPL-Caltech/ASI/USGS/University of Arizona
A still from a video that features a flyover of the Sotra Patera region, along with an explanation of its importance. A link to this video can be found in the bibliography. Credit: NASA/JPL-Caltech/ASI/USGS/University of Arizona
Sotra Patera Region: This is the most likely spot for cyrovolcanism so far seen on Titan. It hosts two large mountains, Doom Mons, the tallest known mountain on Titan, and Erebor Mons. There are other mountains as well, along with pits, including the largest known pit on the moon. It is possible that Doom Mons is or was a cyrovolcano, with Sotra Patera as a caldera or pit. This feature is oval, and is unlikely to be an impact crater. Doom Mons also seems to be the source of flows, which resemble volcanic flows on Earth. Most likely, both Erebor Mons and Doom Mons were cyrovolcanoes, and Sotra Patera is one of several pits on Titan’s surface in this region. Since the flows have no fluvial channels, they are likely not fluvial in origin.
In the end, there is still a variety of possible cyrovolcanic possibilities for Titan. Keep in mind that the authors only had data for 48% of Titan, so many features and discoveries may remain hidden under Titan’s haze of orange. Cyrovolcanism may or may not still be active on Titan, but it is possible, and appears it has happened, though it was not a major part of shaping Titan’s current surface.

 

Bibliography
Astronomy Picture of the Day. “In the Shadow of Saturn’s Rings.” N.p., 3 July 2012. Web.
The site for the first image used in this post, of Saturn and Titan together.
Lopes, R. M. C., et al. (2013), Cryovolcanism on Titan: New results from Cassini RADAR and VIMS, J. GeophysRes. Planets, 118, 416–435, doi:10.1002/jgre.20062.
Today’s main article.
National Aeronautics and Space Administration. “About Saturn & Its Moons: Titan.” Cassini Solstice Mission. N.p., n.d. Web.
A page discussing Titan, with much information on the moon in its tabs.
National Aeronautics and Space Administration. “Introduction: Cassini Solstice Mission.” Cassini Solstice Mission. N.p., n.d. Web.
This page is the home page of the Cassini mission. Cassini has been orbiting Saturn since 2004. In 2005, the associated Huygens probe landed on the surface of Titan. The data used for this article was collected by Cassini.
National Aeronautics and Space Administration, Jet Propulsion Labratory. “Flyover of Sotra Facula, Titan.” N.p., 14 December 2010. Web.
Sotra Patera was formerly known as Sotra Facula. This is the page from which I retrieved the second image used in this post. A direct link to the video the image is from is here.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s