Hopes that Saturn's large moon Titan could possibly support life have taken a serious blow from new data from NASA's Cassini spacecraft. The newly published results reveal that Titan's icy shell is thicker and more rigid than scientists previously thought.
"The ice is much stronger than anyone expected," Doug Hemingway, a planetary sciences doctoral student at the University of California at Santa Cruz, told Discovery News.
Previous studies indicated that Titan might have an ocean hidden beneath its icy shell. In order to learn more about the ocean, scientists needed more information about the shell they believe is covering it. Hemingway dissected the Cassini probe scans of Titan's gravity field, reports NBC. These results were then compared with the moon's structure.
Since the power of the gravitational pull at any point on a surface is dependent on how much mass is beneath that point, the stronger the pull the greater the mass beneath. Scientist expected the highest elevations on Titan to have the most gravity due to the larger amount of mass that they believed was underneath them. But they were astonished to discover that areas of highest elevation on Titan had a weaker gravitational pull than the low elevation areas.
According to Hemingway and his team, this is possible only if the moon’s surface ice is both very rigid and greatly eroded.
"It was very surprising to see that," Hemingway told Space.com. "We assumed at first that we got things wrong, that we were seeing the data backwards, but after we ran out of options to make that finding go away, we came up with a model that explains these observations."
Scientists now believe Titan's subsurface ocean is separated from the surface by a rigid sheet of ice that may be as thick as 62 miles. This icy shell's lack of movement debunks earlier beliefs on Titan's geological activity as well.
"It's good if you have some way of moving material from the top of the ice shell down to the ocean and then back up," UC Santa Cruz scientist Francis Nimmo told Discovery News. "That makes a place more habitable and it also gives you a better chance of detecting things."
But on Titan, "it's hard to envisage a way of transferring material through 100 kilometers' worth of rigid ice down to the ocean, or from the ocean back up to the surface."
Along with their continued study of the icy layer, though, the team is also now looking into the large amount of erosion their model suggests exists deep on Titan's surface. "We now need different groups of people to figure out how so much material could get broken up and transported long distances across Titan's surface," said Hemingway.
As part of this new research, they are looking to determine whether Titan's interior is separated into layers or not. This will provide a better understanding of just how the interior of Titan may have contributed to the large amounts of surface erosion. The details of the scientists findings will appear in this week's Nature.