While icy cryovolcanoes on Titan have been theorized in the past, scientists didn’t have any hard evidence for them. But now, researchers from the Cassini mission have found proof that jumped out of their data in the form of 3-D mountain peaks. Using a new three-dimensional mapping technique, the team was able to create a realistic 3-D flyover of a region on Titan, above, where volcanic-like mountains appear to be lined up in a mountain range-type formation, complete with calderas and material flows. If cryovolcanoes do exist on Titan, they would potentially answer the question of why Titan has so much methane in its atmosphere.
“A combination of features makes us think we’ve found the best evidence so far for icy volcanoes on the moon Titan,” said Randy Kirk, a geophysicist with the U.S. Geological Survey and a member of the Cassini team. “Sotra Facular is a classic volcano with a crater on it and lava flows coming out of it.
Kirk presented the team’s findings at the American Geophysical Union conference in San Francisco.
Rather than erupting hot, molten rock, it is theorized that the cryovolcanoes of Titan would erupt volatiles such as water, methane, and ammonia. “A volcano is a place where material on the inside of a planetary body has gotten warm enough that it can erupt to the surface,” Kirk said. “When a body is made of ice and not rock, you get a cryovolcano.”
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Scientists have suspected cryovolcanoes might populate Titan, and the Cassini mission has collected data on several previous passes of the moon that suggest their existence. Kirk shared radar imagery from early in the Cassini spacecraft’s mission that showed Sotra Facular as bright spot on Titan’s equatorial sand sea, as seen above.
“There were thousands of places where bright ground peeks out of the dark places,” Kirk said, “and in particular we noticed a rose-type round feature, which we called The Rose, with a flows coming from it and we wondered if it was a volcano.”
Combining new data from Cassini’s radar instrument and the visual and infrared mapping spectrometer, the team was able to create the 3-D flyover movie, which shows two peaks more than 1,000 meters (3,000 feet) tall and multiple craters as deep as 1,500 meters (5,000 feet). It also shows finger-like flows. All of these are land features that indicate cryovolcanism.
“We were excited and quite happy when we saw the video,” Kirk told Universe Today at a press briefing on Tuesday. “There was a long time lapse between seeing the image of The Rose, and everybody was wondering if it was a volcano. When we finally managed to create the three dimensional from the topographic maps, I was shocked, and I made it from our own data set! I showed the video to team and they shared that reaction.”
Kirk said the flows were quite thin – thinner than anticipated at less than 100 meters (300 feet) thick — but there were more volcanoes in the same field as Sotra Facula than what the team expected.
In the video, mountains appear, with a huge pit like a volcanic calderas –“ a big bite out of the mountain,” as Kirk described it.
The topography in the video has been vertically exaggerated by a factor of 10. The false color in the initial frames show different compositions of surface material, as detected by Cassini’s visual and infrared mapping spectrometer. In this color scheme, dunes tend to look relatively brown-blue. Blue suggests the presence of some exposed ice. Scientists think the bright areas have an organic coating that hides the ice and is different and lighter than the dunes. The finger-like flows appear bright yellowish-white, like the mountain and caldera. The second set of colors shows elevation, with blue being lowest and yellow and white being the highest. Here, the dunes appear blue because they tend to occupy low areas.
Cryovolcanism could release methane from Titan’s interior, which explains Titan’s seemingly continuous supply of fresh methane in its atmosphere. Without replenishment, scientists say, Titan’s original atmospheric methane should have been exhausted long ago.
“One of mysteries on Titan is the source of methane,” said Linda Spilker, Cassini project scientist, “so cryovoclanoes offer the perfect opportunity to get methane from interior into the atmosphere of Titan.”
Kirk and his team calculated that a Sotra-sized volcanic eruption every 1,000 years would maintain the current level of methane in Titan’s atmosphere.
Jeff Kargel from the University of Arizona, who provided an independent assessment of the potential of cryovolcanoes on Titan, said that no one yet knows what the flows are made of from these volcanoes, but — providing a tantalizing visualization — said an ammonia-water cryolava with methane and carbon dioxide would make frothy, pumice-like deposits on Titan.
Kargel also added that the strongest evidence for cryovolcanoes on Titan is the topographical data that Kirk and his team have provided. “The strong evidence here is the is juxtaposition of the high and low topography in this region on Titan. There are very few tectonic activities that can produce comparable conic mountain like this.”
For more imagery from Kirk’s presentation and other presentations about the Saturn system at AGU, see this NASA webpage.
I just can’t get over the quality of the images and science coming from this spacecraft.
@SteveZodiac: I agree, the images are incredible. Couldn’t the atmospheric methane also be a result of large methane lakes on Titan? Excellent work Cassini team!
Add my voice to the chorus, fantastic. William, I think there is a reasonable case for a Methane cycle with methane rain collecting into lakes and slowly seeping into the ground. There is certainly some exchange between surface liquid and vapor phases…But the question remained how did it replenish the atmosphere. There has to be more coming in all the time because solar radiation catalyzes reactions in the upper atmosphere that consume methane and ammonia to make tholins. So it seems the circle is now completed by actual cryovolcanos. Beautiful.
But where on Titan does all that methane come from? Is it primordial? That is heaps of cosmic methane. Maybe it comes from methanogens. Cyanobacteria-like titanians that live in subtitanian ammoniated water slush. If they can cope with the cold, the ammonia and the pressure …Oh we’ve just got to go back there. We’ll have a back sale.
It is a bit of a bummer if eruptions is the supply, because then there is no guarantee for a continuous supply and so lower chance for a robust biosphere.
@ Procyan:
Currently there are more than enough potential biosignatures on Titan to be excited about, such as hydrogen and acetylene imbalances. As for methanogens, it is iffy IMO.
First, it isn’t cyanobacteria that makes methane, which is pity since they or their ancestors are implied as very old from phototropic growing stromatolites going back 3.5 Gy. It is instead archaea, which from rather small diversity, ease of making rather robust phylogenetic trees from few genes, testing close (likely sister) relationship to eukaryotes, and harboring robust extremophiles are likely among the youngest clades.
Second, methanogenic metabolism _may_ be mechanistically difficult. It derives from simpler methylotropic metabolism which it shares a core of enzymes with. Which btw is an aerobic metabolism, another test for archaea/methanogens as young: they must derive after the Earth oxygenation event at some 2.5 – 2 Gy ago. For whatever reason it may be among the youngest major metabolisms out there, mechanistic difficulty but certainly also evolutionary contingency are implied as potential causes.