While trying to figure out where Saturn’s biggest moon gets all of its methane, a study team found a massive ice structure on Titan. Titan, like Earth, has rain, oceans, and a deteriorating biological surface. However, methane, not water, make up the rains and fills the lakes of Titan. The results of earlier Titan flights were also confirmed by this study, which employed Principal Components Analysis in an unusual method.
Both Earth and Saturn’s biggest moon, Titan, have rain, oceans, and a surface of dissolving biological stuff. On Titan, however, methane, not water, is responsible for the slushy raindrops that fall into the lakes. A team of scientists looking for the source of Titan’s methane uncovered something unexpected: a 4,000-mile-long (6,400 km) ice tunnel that runs almost halfway around the planet. Many of the mysteries of Saturn’s odd moon Titan are hidden under layers and layers of thick haze, but scientists have now looked through the haze in a novel way and discovered a vast stretch of water ice.
Caitlin Griffith is a professor at the University of Arizona’s Lunar and Planetary Laboratory and the main author of a study published in the peer-reviewed journal Nature Astronomy on April 29, 2019. Griffith said in a statement:
“This icy corridor is puzzling because it doesn’t correlate with any surface features nor measurements of the subsurface.”
On Titan, sunlight constantly breaks apart atmospheric methane molecules. The resultant haze rises to the top and collects as organic sediments, rapidly diminishing the atmosphere’s methane supply. This organic veneer is made up of remnants of previous environments. Except for the evaporation of methane from arctic lakes, there is no clear source of methane. Titan’s lakes, on the other hand, barely hold a third of the methane in Titan’s atmosphere.
Titan’s characteristics put an uncanny twist on the world we know and love, therefore scientists are interested in learning more about it. Liquids shower down onto the moon’s surface, filling lakes and seas, thanks to its thick, nitrogen-rich atmosphere. Those liquids, however, are organic molecules dropping onto a water ice-covered surface. It’s strange. It’s also difficult to learn since everything gets in the way of each other.
Subsurface reserves that release methane into the atmosphere might be one source of methane, according to one idea. Prior Titan research has shown the existence of a single area known as Sotra, which resembles a cryovolcano and has ice flow characteristics.
Griffith’s team set out to investigate Titan’s surface composition, partially in the hopes of discovering tiny cryo-volcano possibilities. They studied half of Titan’s surface and found none, but Sotra was determined to be unique in that it had the most pronounced ice characteristics. However, the primary ice feature discovered by the researchers was entirely unanticipated. It’s made up of a 40 percent ice corridor that runs around Titan’s perimeter.
“This icy corridor is puzzling because it doesn’t correlate with any surface features nor measurements of the subsurface,” Griffith said. “Given that our study and past work indicate that Titan is currently not volcanically active, the trace of the corridor is likely a vestige of the past. We detect this feature on steep slopes, but not on all slopes. This suggests that the icy corridor is currently eroding, potentially unveiling the presence of ice and organic strata.”
The researchers set out to investigate the composition of Titan’s surface by examining photos from the NASA Cassini mission’s flybys of Titan, partially in the hopes of discovering tiny cryovolcano candidates. They studied half of Titan’s surface and found none, but they did come upon the ice feature, which was a pleasant surprise. The researchers wrote:
“Titan’s global ice feature presents a puzzle. Ice-rich terrains in other areas of Titan occur only in local regions excavated by craters or exposed by erosion, suggesting that cryovolcanism, if active, is currently not widespread.”
In certain areas, the team’s study reveals a diversity of organic material. Because laboratory models of Titan’s atmosphere create physiologically intriguing molecules like amino acids, these surface deposits are of interest. Griffith used an approach that permitted the detection of faint surface characteristics to examine tens of thousands of spectral pictures obtained of the uppermost layer of the surface by Cassini’s Visible and Infrared Mapping Spectrometer.
Griffith’s use of principal components analysis, or PCA, was crucial in accomplishing this achievement. It enabled her to distinguish tiny characteristics on Titan’s surface generated by ice and organic deposits from the omnipresent haze and more apparent surface features. The PCA recognizes the major and more subtle characteristics by using all of the pixels in an image rather than evaluating the surface features individually for each pixel.
Griffith and his colleagues compared their findings to previous research, such as the Huygens probe, which arrived on Titan in 2005. Both the approach and the findings were confirmed by the comparison. Plans are in the works to utilize the technology to investigate the poles, which are home to methane seas.
“Both Titan and Earth followed different evolutionary paths, and both ended up with unique organic-rich atmospheres and surfaces,” Griffth said. “But it is not clear whether Titan and Earth are common blueprints of the organic-rich of bodies or two among many possible organic-rich worlds.”
The presence of the ice corridor, according to researchers, increases the possibility that tectonic processes had a role in Titan’s creation. The structure appears to be the consequence of a major faulting cracking event that pushed a section of water-ice bedrock upward and exposed it. If this is the true, the feature might provide a glimpse into a layer of Titan that has not yet been explored.