Far below the gaseous atmospheric shroud on Saturn鈥檚 largest moon, Titan, lies Kraken Mare, a sea of liquid methane. Cornell astronomers have estimated that sea to be at least 1,000 feet deep near its center 鈥 enough room for a potential to explore.
After sifting through data from one of the final Titan flybys of the Cassini mission, the researchers detailed their findings in 鈥,鈥 which published Dec. 4, 2020, in the Journal of Geophysical Research.
鈥淭he depth and composition of each of Titan鈥檚 seas had already been measured, except for Titan鈥檚 largest sea, Kraken Mare 鈥 which not only has a great name, but also contains about 80% of the moon鈥檚 surface liquids,鈥 said lead author Valerio Poggiali, research associate in Cornell Center for Astrophysics and Planetary Science (CCAPS), in the 麻豆视频 and 麻豆视频.
A billion miles from Earth, frigid Titan is cloaked in a golden haze of gaseous nitrogen. But peeking through the clouds, the moonscape has an Earthlike appearance, with liquid methane rivers, lakes and seas, according to NASA.
In fact, the data for this discovery was gathered on Cassini鈥檚 T104 flyby of Titan on Aug. 21, 2014. The spacecraft鈥檚 radar surveyed Ligeia Mare 鈥 a smaller sea in the moon鈥檚 northern polar region 鈥 to look for the mysteriously disappearing and reappearing 鈥,鈥 which was an earlier Cornell discovery.
While Cassini cruised at 13,000 mph nearly 600 miles above Titan鈥檚 surface, the spacecraft used its radar altimeter to measure the liquid depth at Kraken Mare and Moray Sinus, an estuary located at the sea鈥檚 northern end. The Cornell scientists, along with engineers from NASA鈥檚 Jet Propulsion Laboratory, had figured out how to discern lake and sea bathymetry (depth) by noting the radar鈥檚 return time differences on the liquid surface and sea bottom, as well as the sea鈥檚 composition by acknowledging the amount of radar energy absorbed during transit through the liquid.
It turns out that Moray Sinus is about 280 feet deep, shallower than the depths of central Kraken Mare, which was too deep for the radar to measure. Surprisingly the liquid鈥檚 composition, primarily a mixture of ethane and methane, was methane-dominated and similar to the composition of nearby Ligeia Mare, Titan鈥檚 second-largest sea.
Earlier scientists had speculated that Kraken may be more ethane rich, both because of its size and extension to the moon鈥檚 lower latitudes. The observation that the liquid composition is not markedly different from the other northern seas is an important finding that will help in assessing models of Titan鈥檚 Earth-like hydrologic system.
Beyond deep, Kraken Mare also is immense 鈥 nearly the size of all five Great Lakes combined.
Titan represents a model environment of a possible atmosphere of early Earth, Poggiali said.
鈥淚n this context,鈥 he said, 鈥渢o understand the depth and composition of Kraken Mare and the Moray Sinus is important because this enables a more precise assessment on Titan鈥檚 methane hydrology. Still, we have to solve many mysteries.鈥
One such puzzle is the origin of the liquid methane. Titan鈥檚 solar light 鈥 about 100 times less intense than on Earth 鈥 constantly converts methane in the atmosphere into ethane; over roughly 10 million-year periods, this process would completely deplete Titan鈥檚 surface stores, according to Poggiali.
In the distant future, a submarine 鈥 likely without a mechanical engine 鈥 will visit and cruise Kraken Mare, Poggiali said.
鈥淭hanks to our measurements,鈥 he said, 鈥渟cientists can now infer the density of the liquid with higher precision, and consequently better calibrate the sonar aboard the vessel and understand the sea鈥檚 directional flows.鈥
Co-authors on the paper are: Alex Hayes, professor of astronomy and director of CCAPS; Jonathan Lunine, the David C. Duncan Professor in the Physical 麻豆视频, and chair, Department of Astronomy; Marco Mastrogiuseppe, former Cornell postdoctoral researcher, now research associate at Sapienza University of Rome, Italy; Alice Le Gall, The Institut Universitaire de France, Paris; and research associates Illeana Gomez-Leal and Daniel Lalich.
NASA provided funding for this research.
.
More News from A&S
Social sciences
AI in science
